Richard S Glass

Interests

No activities entered.

Courses

Scholarly Contributions

Journals/Publications

• Abul-Futouh, H., Almazahreh, L. R., Sakamoto, T., Stessman, N. Y., Lichtenberger, D. L., Glass, R. S., Görls, H., El-Khateeb, M., Schollhammer, P., Mloston, G., & Weigand, W. (2017). [FeFe]-Hydrogenase H-Cluster Mimics with Unique Planar μ-(SCH2 )2 ER2 Linkers (E=Ge and Sn). Chemistry (Weinheim an der Bergstrasse, Germany), 23(2), 346-359.
  More info

  Analogues of the [2Fe-2S] subcluster of hydrogenase enzymes in which the central group of the three-atom chain linker between the sulfur atoms is replaced by GeR2 and SnR2 groups are studied. The six-membered FeSCECS rings in these complexes (E=Ge or Sn) adopt an unusual conformation with nearly co-planar SCECS atoms perpendicular to the Fe-Fe core. Computational modelling traces this result to the steric interaction of the Me groups with the axial carbonyls of the Fe2 (CO)6 cluster and low torsional strain for GeMe2 and SnMe2 moieties owing to the long C-Ge and C-Sn bonds. Gas-phase photoelectron spectroscopy of these complexes shows a shift of ionization potentials to lower energies with substantial sulfur orbital character and, as supported by the computations, an increase in sulfur character in the predominantly metal-metal bonding HOMO. Cyclic voltammetry reveals that the complexes follow an ECE-type reduction mechanism (E=electron transfer and C=chemical process) in the absence of acid and catalysis of proton reduction in the presence of acid. Two cyclic tetranuclear complexes featuring the sulfur atoms of two Fe2 S2 (CO)6 cores bridged by CH2 SnR2 CH2 , R=Me, Ph, linkers were also obtained and characterized.
• Almazahreh, L. R., Abdul-Futouh, H., Sakamoto, T., Stessman, N., Lichtenberger, D. L., Glass, R. S., El-khateeb, M., & Weigand, W. (2017). [FeFe]​-​Hydrogenase H-​Cluster Mimics with Unique Planar μ-​(SCH2)​2ER2 Linkers (E = Ge and Sn). Chemistry, A European Journal, 23(2), 346-359.
• Dirlam, P. T., Park, J., Simmonds, A. G., Domanik, K., Arrington, C. B., Schaefer, J. L., Oleshko, V. P., Kleine, T. S., Char, K., Glass, R. S., Soles, C. L., Kim, C., Pinna, N., Sung, Y. E., & Pyun, J. (2016). Elemental Sulfur and Molybdenum Disulfide Composites for Li-S Batteries with Long Cycle Life and High-Rate Capability. ACS applied materials & interfaces, 8(21), 13437-48.
  More info

  The practical implementation of Li-S technology has been hindered by short cycle life and poor rate capability owing to deleterious effects resulting from the varied solubilities of different Li polysulfide redox products. Here, we report the preparation and utilization of composites with a sulfur-rich matrix and molybdenum disulfide (MoS2) particulate inclusions as Li-S cathode materials with the capability to mitigate the dissolution of the Li polysulfide redox products via the MoS2 inclusions acting as "polysulfide anchors". In situ composite formation was completed via a facile, one-pot method with commercially available starting materials. The composites were afforded by first dispersing MoS2 directly in liquid elemental sulfur (S8) with sequential polymerization of the sulfur phase via thermal ring opening polymerization or copolymerization via inverse vulcanization. For the practical utility of this system to be highlighted, it was demonstrated that the composite formation methodology was amenable to larger scale processes with composites easily prepared in 100 g batches. Cathodes fabricated with the high sulfur content composites as the active material afforded Li-S cells that exhibited extended cycle lifetimes of up to 1000 cycles with low capacity decay (0.07% per cycle) and demonstrated exceptional rate capability with the delivery of reversible capacity up to 500 mAh/g at 5 C.
• Yamamoto, T., Dai, J., Jacobsen, N. E., Ammam, M., Hall, G. B., Mozziconacci, O., Schöneich, C., Wilson, G. S., & Glass, R. S. (2016). Neighboring π-Amide Participation in Thioether Oxidation: Conformational Control. Organic letters, 18(15), 3522-5.
  More info

  The electrochemical oxidation of thioethers is shown to be facilitated by neighboring amide participation. (1)H NMR spectroscopic analysis in acetonitrile solution of two conformationally constrained compounds with such facilitation shows that two-electron participation by the amide π2 orbital can occur to stabilize the developing sulfur radical cation.
• Dirlam, P. T., Simmonds, A. G., Kleine, T. S., Nguyen, N. A., Anderson, L. E., Klever, A. O., Florian, A., Costanzo, P. J., Theato, P., Mackay, M. E., Glass, R. S., Char, K., & Pyun, J. (2015). Inverse vulcanization of elemental sulfur with 1,4-diphenylbutadiyne for cathode materials in Li-S batteries. RSC ADVANCES, 5(31), 24718-24722.
• Dirlam, P. T., Simmonds, A. G., Shallcross, R. C., Arrington, K. J., Chung, W. J., Griebel, J. J., Hill, L. J., Glass, R. S., Char, K., & Pyun, J. (2015). Improving the Charge Conductance of Elemental Sulfur via Tandem Inverse Vulcanization and Electropolymerization. ACS MACRO LETTERS, 4(1), 111-114.
  More info

  The synthesis of polymeric materials using elemental sulfur (S8) as the chemical feedstock has recently been developed using a process termed inverse vulcanization. The preparation of chemically stable sulfur copolymers was previously prepared by the inverse vulcanization of S-8 and 1,3-diisopropenylbenzene (DIB); however, the development of synthetic methods to introduce new chemical functionality into this novel class of polymers remains an important challenge. In this report the introduction of polythiophene segments into poly(sulfur-random-1,3-diisopropenylbenzene) is achieved by the inverse vulcanization of S-8 with a styrenic functional 3,4-propylenedioxythiophene (ProDOT-Sty) and DIB, followed by electropolymerization of ProDOT side chains. This methodology demonstrates for the first time a facile approach to introduce new functionality into sulfur and high sulfur content polymers, while specifically enhancing the charge conductivity of these intrinsically highly resistive materials.
• Griebel, J. J., Li, G., Glass, R. S., Char, K., & Pyun, J. (2015). Kilogram Scale Inverse Vulcanization of Elemental Sulfur to Prepare High Capacity Polymer Electrodes for Li-S Batteries. JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY, 53(2), 173-177.
  More info

  The synthesis of high content sulfur copolymers via the inverse vulcanization of elemental sulfur and 1,3-diisopropenylbenzene (DIB) on a one-kilogram scale is reported in a single step process. Investigation into the effects of temperature, reaction scale, and comonomer feed ratios on the inverse vulcanization process of S-8 and DIB were explored to suppress the Trommsdorf effect and enable large scale synthesis of these copolymers. The copolymers were then successfully used as the active cathode materials in Li-S batteries, exhibiting enhanced capacity retention and battery lifetimes (608 mAh/g at 640 cycles) at a C/10 rate. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 173-177
• Monney, N. P., Bally, T., Yamamoto, T., & Glass, R. S. (2015). Spectroscopic Evidence for Through-Space Arene-Sulfur-Arene Bonding Interaction in m-Terphenyl Thioether Radical Cations. The journal of physical chemistry. A, 119(52), 12990-8.
  More info

  Electronic absorption spectra and quantum chemical calculations of the radical cations of m-terphenyl tert-butyl thioethers, where the S-t-Bu bond is forced to be perpendicular to the central phenyl ring, show the occurrence of through-space [π···S···π](+) bonding interactions which lead to a stabilization of the thioether radical cations. In the corresponding methyl derivatives there is a competition between delocalization of the hole that is centered on a p-AO of the S atom into the π-system of the central phenyl ring or through space into the flanking phenyl groups, which leads to a mixture of planar and perpendicular conformations in the radical cation. Adding a second m-terphenyl tert-butyl thioether moiety does not lead to further delocalization; the spin and charge remain in one of the two halves of the radical cation. These findings have interesting implications with regard to the role of methionines as hopping stations in electron transfer through proteins.
• Griebel, J. J., Namnabat, S., Kim, E. T., Himmelhuber, R., Moronta, D. H., Chung, W. J., Simmonds, A. G., Kim, K., van der Laan, J., Nguyen, N. A., Dereniak, E. L., Mackay, M. E., Char, K., Glass, R. S., Norwood, R. A., & Pyun, J. (2014). New Infrared Transmitting Material via Inverse Vulcanization of Elemental Sulfur to Prepare High Refractive Index Polymers. ADVANCED MATERIALS, 26(19), 3014-3018.
• Griebel, J. J., Namnabat, S., Kim, E. T., Himmelhuber, R., Moronta, D. H., Chung, W. J., Simmonds, A. G., Kim, K., van der Laan, J., Nguyen, N. A., Dereniak, E. L., Mackay, M. E., Char, K., Glass, R. S., Norwood, R. A., & Pyun, J. (2014). New infrared transmitting material via inverse vulcanization of elemental sulfur to prepare high refractive index polymers. Advanced materials (Deerfield Beach, Fla.), 26(19), 3014-8.
  More info

  Polymers for IR imaging: The preparation of high refractive index polymers (n = 1.75 to 1.86) via the inverse vulcanization of elemental sulfur is reported. High quality imaging in the near (1.5 μm) and mid-IR (3-5 μm) regions using high refractive index polymeric lenses from these sulfur materials was demonstrated.
• Griebel, J. J., Nguyen, N. A., Astashkin, A. V., Glass, R. S., Mackay, M. E., Char, K., & Pyun, J. (2014). Preparation of Dynamic Covalent Polymers via Inverse Vulcanization of Elemental Sulfur. ACS MACRO LETTERS, 3(12), 1258-1261.
  More info

  The synthesis of dynamic covalent polymers with controllable amounts of sulfur sulfur (S-S) bonds in the polymer backbone via inverse vulcanization of elemental sulfur (S-8) and 1,3-diisopropenylbenzene (DIB) is reported. An attractive feature of the inverse vulcanization process is the ability to control the number and dynamic nature of S-S bonds in poly(sulfur-random-(1,3-diisopropenylbenzene)) (poly(S-r-DIB) copolymers by simple variation of S-8/1201B feed ratios in the copolymerization. S-S bonds in poly(S-r-DIB) copolymers of high sulfur content and sulfur rank were found to be more dynamic upon exposure to either heat, or mechanical stimuli. Interrogation of dynamic S-S bonds was conducted in the solid-state utilizing electron paramagnetic resonance spectroscopy and in situ rheological measurements. Time-dependent theological property behavior demonstrated a compositional dependence of the healing behavior in the copolymers, with the highest sulfur (80 wt % sulfur) content affording the most rapid dynamic response and recovery of theological properties.
• Hall, G. B., Kottani, R., A., G., Yamamoto, T., Evans, D. H., Glass, R. S., & Lichtenberger, D. L. (2014). Intramolecular electron transfer in bipyridinium disulfides. Journal of the American Chemical Society, 136(10), 4012-4018.
  More info

  Abstract: Reductive cleavage of disulfide bonds is an important step in many biological and chemical processes. Whether cleavage occurs stepwise or concertedly with electron transfer is of interest. Also of interest is whether the disulfide bond is reduced directly by intermolecular electron transfer from an external reducing agent or mediated intramolecularly by internal electron transfer from another redox-active moiety elsewhere within the molecule. The electrochemical reductions of 4,4′-bipyridyl-3,3′-disulfide (1) and the di-N-methylated derivative (22+) have been studied in acetonitrile. Simulations of the cyclic voltammograms in combination with DFT (density functional theory) computations provide a consistent model of the reductive processes. Compound 1 undergoes reduction directly at the disulfide moiety with a substantially more negative potential for the first electron than for the second electron, resulting in an overall two-electron reduction and rapid cleavage of the S-S bond to form the dithiolate. In contrast, compound 22+ is reduced at less negative potential than 1 and at the dimethyl bipyridinium moiety rather than at the disulfide moiety. Most interesting, the second reduction of the bipyridinium moiety results in a fast and reversible intramolecular two-electron transfer to reduce the disulfide moiety and form the dithiolate. Thus, the redox-active bipyridinium moiety provides a low energy pathway for reductive cleavage of the S-S bond that avoids the highly negative potential for the first direct electron reduction. Following the intramolecular two-electron transfer and cleavage of the S-S bond the bipyridinium undergoes two additional reversible reductions at more negative potentials. © 2014 American Chemical Society.
• Hall, G. B., Kottani, R., Felton, G. A., Yamamoto, T., Evans, D. H., Glass, R. S., & Lichtenberger, D. L. (2014). Intramolecular Electron Transfer in Bipyridinium Disulfides. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136(10), 4012-4018.
  More info

  Reductive cleavage of disulfide bonds is an important step in many biological and chemical processes. Whether cleavage occurs stepwise or concertedly with electron transfer is of interest. Also of interest is whether the disulfide bond is reduced directly by intermolecular electron transfer from an external reducing agent or mediated intramolecularly by internal electron transfer from another redox-active moiety elsewhere within the molecule. The electrochemical reductions of 4,4'-bipyridyl-3,3'-disulfide (1) and the di-N-methylated derivative (2(2+)) have been studied in acetonitrile. Simulations of the cyclic voltammograms in combination with DFT (density functional theory) computations provide a consistent model of the reductive processes. Compound 1 undergoes reduction directly at the disulfide moiety with a substantially more negative potential for the first electron than for the second electron, resulting in an overall two-electron reduction and rapid cleavage of the S S bond to form the dithiolate. In contrast, compound 2(2+) is reduced at less negative potential than 1 and at the dimethyl bipyridinium moiety rather than at the disulfide moiety. Most interesting, the second reduction of the bipyridinium moiety results in a fast and reversible intramolecular two-electron transfer to reduce the disulfide moiety and form the dithiolate. Thus, the redox-active bipyridinium moiety provides a low energy pathway for reductive cleavage of the S S bond that avoids the highly negative potential for the first direct electron reduction. Following the intramolecular two-electron transfer and cleavage of the S S bond the bipyridinium undergoes two additional reversible reductions at more negative potentials.
• Hall, G. B., Kottani, R., Felton, G. A., Yamamoto, T., Evans, D. H., Glass, R. S., & Lichtenberger, D. L. (2014). Intramolecular electron transfer in bipyridinium disulfides. Journal of the American Chemical Society, 136(10), 4012-8.
  More info

  Reductive cleavage of disulfide bonds is an important step in many biological and chemical processes. Whether cleavage occurs stepwise or concertedly with electron transfer is of interest. Also of interest is whether the disulfide bond is reduced directly by intermolecular electron transfer from an external reducing agent or mediated intramolecularly by internal electron transfer from another redox-active moiety elsewhere within the molecule. The electrochemical reductions of 4,4'-bipyridyl-3,3'-disulfide (1) and the di-N-methylated derivative (2(2+)) have been studied in acetonitrile. Simulations of the cyclic voltammograms in combination with DFT (density functional theory) computations provide a consistent model of the reductive processes. Compound 1 undergoes reduction directly at the disulfide moiety with a substantially more negative potential for the first electron than for the second electron, resulting in an overall two-electron reduction and rapid cleavage of the S-S bond to form the dithiolate. In contrast, compound 2(2+) is reduced at less negative potential than 1 and at the dimethyl bipyridinium moiety rather than at the disulfide moiety. Most interesting, the second reduction of the bipyridinium moiety results in a fast and reversible intramolecular two-electron transfer to reduce the disulfide moiety and form the dithiolate. Thus, the redox-active bipyridinium moiety provides a low energy pathway for reductive cleavage of the S-S bond that avoids the highly negative potential for the first direct electron reduction. Following the intramolecular two-electron transfer and cleavage of the S-S bond the bipyridinium undergoes two additional reversible reductions at more negative potentials.
• Harb, M. K., Daraosheh, A., Goerls, H., Smith, E. R., Meyer, G. J., Swenson, M. T., Sakamoto, T., Glass, R. S., Lichtenberger, D. L., Evans, D. H., El-khateeb, M., & Weigand, W. (2014). Effects of Alkane Linker Length and Chalcogen Character in [FeFe]-Hydrogenase Inspired Compounds. HETEROATOM CHEMISTRY, 25(6), 592-606.
  More info

  Models of [FeFe]-hydrogenases containing diselenolato ligands with different bridge linker length have been prepared: Fe-2(mu-Se(CH2)(4)Se-mu)(CO)(6) (4DS), and Fe-2(mu-Se(CH2)(5)Se-mu)(CO)(6) (5DS) as well as dithiolato Fe-2(mu-S(CH2)(4)S-mu)(CO)(6) (4DT) and compared with Fe-2(mu-S(CH2)(3)S-mu)(CO)(6) (PDT) and Fe-2(mu-Se(CH2)(3)Se-mu)(CO)(6) (PDS). Compounds 4DT, PDS, 4DS, and 5DS were characterized by spectroscopic techniques including NMR, IR, mass spectrometry, ultraviolet photoelectron spectroscopy (UPS), elemental analysis, and X-ray crystal structure analysis. Combinations of electrochemical measurements, UPS, and density functional theory calculations indicate that oxidations of these five compounds are not significantly affected by chalcogen character but instead are governed by linker length. Cations for all compounds are calculated to adopt a bridged CO "rotated" structure with a vacant site on one of the Fe centers. In 4DT, 4DS, and 5DS, the alkane linker forms an agostic interaction with the vacant site on the rotated Fe. The reduction potentials for these compounds shift positively on average 0.16 V for each carbon added to the alkane linker with shifts being as large as 0.23 V between PDT and 4DT, and as small as 0.09 V between 4DS and 5DS. Catalytic reduction of protons from acetic acid in CH2Cl2 occurs at -1.79 and -1.86 V for PDT and 4DT and -2.02, -2.09, and -2.04 V for PDS, 4DS, and 5DS, indicating that chalcogen character is the primary factor that affects catalytic potential. On average the S-containing compounds catalyze proton reduction at potentials, which are 0.23 V less negative than the Se-containing compounds in this study. (C) 2014 Wiley Periodicals, Inc.
• In-noi, O., Haller, K. J., Hall, G. B., Brezinski, W. P., Marx, J. M., Sakamoto, T., Evans, D. H., Glass, R. S., & Lichtenberger, D. L. (2014). Electrochemical, Spectroscopic, and Computational Study of Bis(mu-methylthiolato)diironhexacarbonyl: Homoassociative Stabilization of the Dianion and a Chemically Reversible Reduction/Reoxidation Cycle. ORGANOMETALLICS, 33(18), 5009-5019.
  More info

  The redox characteristics of (mu-SMe)(2)Fe-2(CO)(6) from the 1+ to 2- charge states are reported. This [2Fe-2S] compound is related to the active sites of [FeFe]-hydrogenases but notably without a linker between the sulfur atoms. The 1+ charge state was studied both by ionization in the gas phase by photoelectron spectroscopy and by oxidation in the solution phase by cyclic voltammetry. The adiabatic ionization is to a cation whose structure features a semibridging carbonyl, similar to the structure of the active site of [FeFe]-hydrogenases in the same oxidation state. The reduction of the compound by cyclic voltammetry gives an electrochemically irreversible cathodic peak, which often suggests disproportionation or other irreversible chemical processes in this class of molecules. However, the return scan through electrochemically irreversible oxidation peaks that occur at potentials around 1 V more positive than the reduction led to the recovery of the initial neutral compound. The dependence of the CVs on scan rate, IR spectroelectrochemistry of reduction and oxidation cycles, chronocoulometry, and DFT computations indicate a mechanism in which stabilization of the dianion plays a key role. Initial one-electron reduction of the compound is accompanied in the same cathodic peak with a second slower electron reduction to the dianion. Geometric reorganization and solvation stabilize the [2Fe-2S](2-) dianion such that the potential for addition of the second electron is slightly less negative than that of the first (potential inversion). The return oxidation peaks at more positive potentials follow from rapid pairing of the dianion with another neutral molecule in solution (termed homoassociation) to form a stabilized [4Fe-4S](2-) dianion. Two one-electron oxidations of this [4Fe-4S](2-) dianion result in regeneration of the initial neutral compound. The implications of this homoassociation for the [FeFe]-hydrogenase enzyme, in which the H-cluster active site features a [2Fe-2S] site associated with a [4Fe-4S] cubane cluster via a thiolate bridge, are discussed.
• Kim, E. T., Chung, W. J., Lim, J., Johe, P., Glass, R. S., Pyun, J., & Char, K. (2014). One-pot synthesis of PbS NP/sulfur-oleylamine copolymer nanocomposites via the copolymerization of elemental sulfur with oleylamine. POLYMER CHEMISTRY, 5(11), 3617-3623.
  More info

  A novel synthetic and processing strategy for converting elemental sulfur into polymeric and nanocomposite materials is reported. We describe a facile one-pot reaction using elemental sulfur and oleylamine as comonomers to prepare high sulfur content copolymers and lead sulfide nanoparticle (PbS NP) nanocomposites. This process enables the preparation of solution processable copolymers and nanocomposites, where the loading and dispersion of PbS NP inclusions could be precisely controlled. We demonstrate the dual roles of oleylamine with sulfur for both the copolymerization of sulfur copolymers as well as the in situ synthesis of PbS NPs in a one-pot fashion.
• Simmonds, A. G., Griebel, J. J., Park, J., Kim, K. R., Chung, W. J., Oleshko, V. P., Kim, J., Kim, E. T., Glass, R. S., Soles, C. L., Sung, Y., Char, K., & Pyun, J. (2014). Inverse Vulcanization of Elemental Sulfur to Prepare Polymeric Electrode Materials for Li-S Batteries. ACS MACRO LETTERS, 3(3), 229-232.
  More info

  Sulfur-rich copolymers based on poly(sulfur-random-1,3-diisopropenylbenzene) (poly(S-r-DIB)) were synthesized via inverse vulcanization to create cathode materials for lithium sulfur battery applications. These materials exhibit enhanced capacity retention (1005 mAh/g at 100 cycles) and battery lifetimes over 500 cycles at a C/10 rate. These poly(S-r-DIB) copolymers represent a new class of polymeric electrode materials that exhibit one of the highest charge capacities reported, particularly after extended charge discharge cycling in Li-S batteries.
• Chung, W. J., Bhagavathy, G. V., Jacobsen, N. E., Senef, S., & Glass, R. S. (2013). An unusual epimerization of a thioether. Journal of Sulfur Chemistry, 34(1-2), 67-78.
  More info

  Abstract: Reaction of 6-exo-methylthio-2-exo-phenylbicyclo[2.2.1]heptan-2-endo-ol with sodium azide and acid afforded the corresponding 2-exo-azide. This azide was reduced and acetylated to give a crystalline derivative whose structure was unequivocally established by X-ray crystallographic analysis. Surprisingly, the isomeric 6-endo-methylthio-2-exo-phenylbicyclo[2.2.1]heptan-2-endo-ol on reaction with sodium azide and acid yielded the same azide as the 6-exo-methylthio analogue. Evidence for the mechanism of thioisomerization is presented. © 2013 Copyright Taylor and Francis Group, LLC.© 2013 Copyright Taylor and Francis Group, LLC.
• Chung, W. J., Griebel, J. J., Kim, E. T., Yoon, H., Simmonds, A. G., Ji, H. J., Dirlam, P. T., Glass, R. S., Wie, J. J., Nguyen, N. A., Guralnick, B. W., Park, J., Somogyi, A., Theato, P., Mackay, M. E., Sung, Y., Char, K., & Pyun, J. (2013). The use of elemental sulfur as an alternative feedstock for polymeric materials. Nature chemistry, 5(6), 518-24.
  More info

  An excess of elemental sulfur is generated annually from hydrodesulfurization in petroleum refining processes; however, it has a limited number of uses, of which one example is the production of sulfuric acid. Despite this excess, the development of synthetic and processing methods to convert elemental sulfur into useful chemical substances has not been investigated widely. Here we report a facile method (termed 'inverse vulcanization') to prepare chemically stable and processable polymeric materials through the direct copolymerization of elemental sulfur with vinylic monomers. This methodology enabled the modification of sulfur into processable copolymer forms with tunable thermomechanical properties, which leads to well-defined sulfur-rich micropatterned films created by imprint lithography. We also demonstrate that these copolymers exhibit comparable electrochemical properties to elemental sulfur and could serve as the active material in Li-S batteries, exhibiting high specific capacity (823 mA h g(-1) at 100 cycles) and enhanced capacity retention.
• Chung, W. J., Griebel, J. J., Kim, E. T., Yoon, H., Simmonds, A. G., Ji, H. J., Dirlam, P. T., Glass, R. S., Wie, J. J., Nguyen, N. A., Guralnick, B. W., Park, J., Somogyi, Á., Theato, P., Mackay, M. E., Sung, Y., Char, K., & Pyun, J. (2013). The use of elemental sulfur as an alternative feedstock for polymeric materials. Nature Chemistry, 5(6), 518-524.
  More info

  PMID: 23695634;Abstract: An excess of elemental sulfur is generated annually from hydrodesulfurization in petroleum refining processes; however, it has a limited number of uses, of which one example is the production of sulfuric acid. Despite this excess, the development of synthetic and processing methods to convert elemental sulfur into useful chemical substances has not been investigated widely. Here we report a facile method (termed 'inverse vulcanization') to prepare chemically stable and processable polymeric materials through the direct copolymerization of elemental sulfur with vinylic monomers. This methodology enabled the modification of sulfur into processable copolymer forms with tunable thermomechanical properties, which leads to well-defined sulfur-rich micropatterned films created by imprint lithography. We also demonstrate that these copolymers exhibit comparable electrochemical properties to elemental sulfur and could serve as the active material in Li-S batteries, exhibiting high specific capacity (823 mA h g-1 at 100 cycles) and enhanced capacity retention. © 2013 Macmillan Publishers Limited.
• Glass, R., Monney, N. P., Bally, T., Bhagavathy, G. S., & Glass, R. S. (2013). Spectroscopic Evidence for a New Type of Bonding between a Thioether Radical Cation and a Phenyl Group. Organic letters, 15(19).
  More info

  The oxidation potential of thioethers constrained to be near aromatic rings is lowered, due to an antibonding interaction between the p-type sulfur lone pair with the neighboring phenyl π-system which on removal of an electron becomes a new kind of 3-electron S∴π bonding that reveals itself in the photoelectron spectrum and by an electronic transition involving the orbitals participating in the S∴π bond.
• Hall, G. B., Chen, J., Mebi, C. A., Okumura, N., Swenson, M. T., Ossowski, S. E., Zakai, U. I., Nichol, G. S., Lichtenberger, D. L., Evans, D. H., & Glass, R. S. (2013). Redox chemistry of noninnocent quinones annulated to 2Fe2S cores. Organometallics, 32(21), 6605-6612.
  More info

  Abstract: Noninnocent ligands that are electronically coupled to active catalytic sites can influence the redox behavior of the catalysts. A series of (μ-dithiolato)Fe2(CO)6 complexes, in which the sulfur atoms of the μ-dithiolato ligand are bridged by 5-substituted (Me, OMe, Cl, t-Bu)-1,4-benzoquinones, 1,4-naphthoquinone, or 1,4-anthraquinone, have been synthesized and characterized. In addition, the bis-phosphine complex derived from the 1,4-naphthoquinone-bridged complex has also been prepared and characterized. Cyclic voltammetry of these complexes shows two reversible one-electron reductions at potentials 0.2 to 0.5 V less negative than their corresponding parent quinones. In the presence of acetic acid two-electron reductions of the complexes result in conversion of the quinones to hydroquinone moieties. EPR spectroscopic and computational studies of the one-electron-reduced complexes show electron delocalization from the semiquinones to the 2Fe2S moieties, thereby revealing the " noninnocent" behavior of these ligands with these catalysts. © 2013 American Chemical Society.
• Monney, N. P., Bally, T., Bhagavathy, G. S., & Glass, R. S. (2013). Spectroscopic evidence for a new type of bonding between a thioether radical cation and a phenyl group. Organic Letters, 15(19), 4932-4935.
  More info

  PMID: 24059648;Abstract: The oxidation potential of thioethers constrained to be near aromatic rings is lowered, due to an antibonding interaction between the p-type sulfur lone pair with the neighboring phenyl π-system which on removal of an electron becomes a new kind of 3-electron Sπ bonding that reveals itself in the photoelectron spectrum and by an electronic transition involving the orbitals participating in the Sπ bond. © 2013 American Chemical Society.
• Seidel, R. A., Hall, G. B., Swenson, M. T., Nichol, G. S., Lichtenberger, D. L., Evans, D. H., & Glass, R. S. (2013). Synthesis and characterization of [FeFe]-hydrogenase mimics appended with a 2-phenylazopyridine ligand. Journal of Sulfur Chemistry, 34(6), 566-579.
  More info

  Abstract: Two new complexes in which 2-phenylazopyridine (pap) chelates iron in hydrogenase mimics, 1,2-(-benzenedithiolato)-2′- phenylazopyridinediirontetracarbonyl and 1,3-(-propanedithiolato)-2′- phenylazo- pyridinediirontetracarbonyl have been synthesized and fully characterized, including X-ray crystal structure determinations. The electronic structures of the two complexes are compared with the analogous 1,2-(-benzenedithiolato)diironhexacarbonyl and 1,3-(-propanedithiolato) diironhexacarbonyl complexes. Based on comparison of the crystal structures, the overall bonding in the 2Fe2S core of the molecules is little perturbed by replacing two carbonyl ligands with the pap ligand. Also, the coordinated pap ligand retains a similar structure and NN bond distance to that of the uncoordinated ligand. However, the charge asymmetry in the 2Fe2S core that results from chelating the pap ligand on one of the iron atoms induces substantial localization of the individual orbital characters in the 2Fe2S core. Most interesting, the pap-substituted complexes feature a novel strong long wavelength absorption in the visible region that imparts a deep blue color to the molecules. TDDFT calculations reveal the nature of this absorption as excitation to a low-lying empty orbital on the pap ligand mixed with filled primarily metal d orbitals of the 2Fe2S core. © 2013 Taylor & Francis.
• Apfel, U., Görls, H., A., G., Evans, D. H., Glass, R. S., Lichtenberger, D. L., & Weigand, W. (2012). {1,1'-(Dimethylsilylene)bis[methanechalcogenolato]}diiron complexes [2Fe2E(Si)] (E=S, Se, Te)-[FeFe] hydrogenase models. Helvetica Chimica Acta, 95(11), 2168-2175.
  More info

  Abstract: (Bis-selenolato) and (bis-tellurolato)diiron complexes [2Fe2E(Si)] were prepared and compared with the known (bis-thiolato)diiron complex A to assess their ability to produce hydrogen from protons. Treatment of [Fe 3(CO)12] with 4,4-dimethyl-1,2,4-diselenasilolane (1) in boiling toluene afforded hexacarbonyl{μ-{[1,1'-(dimethylsilylene) bis[methaneselenolato-κSe: κSe]](2 -)}}diiron(Fe-Fe) (2). The analog bis-tellurolato complex hexacarbonyl{μ-{[1,1'-(dimethylsilylene) bis[methanetellurolato-κTe: κTe]](2 -)}}diiron(Fe-Fe) (3) was obtained by treatment of [Fe3(CO)12] with dimethylbis(tellurocyanatomethyl)dimethylsilane, which was prepared in situ. All compounds were characterized by NMR, IR spectroscopy, mass spectrometry, elemental analysis and single-crystal X-ray analysis. The electrocatalytic properties of the [2Fe2X(Si)] (X=S, Se, Te) model complexes A, 1, and 2 towards hydrogen formation were evaluated. © 2012 Verlag Helvetica Chimica Acta AG, Zürich, Switzerland.
• Harb, M. K., Windhager, J., Niksch, T., Görls, H., Sakamoto, T., Smith, E. R., Glass, R. S., Lichtenberger, D. L., Evans, D. H., El-Khateeb, M., & Weigand, W. (2012). Comparison of S and Se dichalcogenolato [FeFe]-hydrogenase models with central S and Se atoms in the bridgehead chain. Tetrahedron, 68(51), 10592-10599.
  More info

  Abstract: In order to study the influence of sulfur and selenium atoms incorporated into the structure of complexes that model the active site of [FeFe]-hydrogenases, a series of diiron dithiolato and diselenolato complexes of the form (μ-ECH 2XCH 2E-μ)Fe 2(CO) 6 have been prepared and characterized, where the diiron bridging atoms E are S or Se, and the linker bridgehead X is CH 2, S, or Se. The electron energies have been compared by gas-phase photoelectron spectroscopy, and the oxidation, and reduction behaviors, as well as the ability to reduce protons from acetic acid to form H 2, have been compared by cyclic voltammetry. Density functional theory computations agree well with the structures and electron energies of these molecules, and shed additional light on the oxidation and reduction properties. The computations indicate that the HOMO of each molecule where the bridgehead X is S or Se contains substantial chalcogen 'lone pair' orbital character. The presence of the bridgehead chalcogen lone pairs favors the Fe(CO) 3 'rotated' structures for both the cations and dianions of these complexes, but in different ways. In the cations one Fe(CO) 3 rotates to put one carbonyl ligand in a semibridging position, and the bridgehead chalcogen lone pair electrons donate to the vacant coordination site created on the iron to stabilize the positive charge. In the dianions one Fe(CO) 3 rotates to put one carbonyl ligand in a fully bridging position, and one bridging chalcogen atom breaks its bond with an iron atom, pulling the bridgehead chalcogen lone pair away from the iron to minimize the electron-electron repulsions. © 2012 Elsevier Ltd. All rights reserved.
• Yamamoto, T., Chen, P., Lin, G., B̈och-Mechkour, A., Jacobsen, N. E., Bally, T., & Glass, R. S. (2012). Synthesis and rotation barriers in 2, 6-Di-(o-anisyl) anisole. Journal of Physical Organic Chemistry, 25(10), 878-882.
  More info

  Abstract: Variable temperature 1H NMR spectroscopic studies of 2, 6-di(o-anisyl) anisole show syn and anti atropisomers at low temperature. The barrier for interconverting these isomers by rotation about the aryl-aryl bond, found by fitting the experimental data, is 41.2 kJ/mol. Copyright © 2012 John Wiley & Sons, Ltd.
• Chen, J., Vannucci, A. K., Mebi, C. A., Okumura, N., Borowski, S. C., Lockett, L. T., Swenson, M., Lichtenberger, D. L., Evans, D. H., & Glass, R. S. (2011). Catalysis of electrochemical reduction of weak acids to produce H ₂: Role of O-H..S hydrogen bonding. Phosphorus, Sulfur and Silicon and the Related Elements, 186(5), 1288-1292.
  More info

  Abstract: The role of intramolecular OH.. S hydrogen bonding in the electrochemical reduction of protons from acetic acid using biomimetically inspired catalysts has been studied. The catalysts, hydroquinone moieties annulated to an Fe 2S2(CO)6 core, were synthesized by piperidine-mediated conjugate addition of the dithiol Fe2(SH) 2(CO)6 to quinones in 26-76% yields. These complexes catalyze electrochemical H2 production from acetic acid. Evidence for weak intramolecular OH.. Shydrogen bonding in the neutral complexes is presented. Such hydrogen bonding becomes stronger as the charge increases on the sulfur in the electrochemically produced dianions due to "charge assistance," and this has chemical consequences. Copyright © Taylor & Francis Group, LLC.
• Chung, W. J., Simmonds, A. G., Griebel, J. J., Kim, E. T., Suh, H. S., Shim, I., Glass, R. S., Loy, D. A., Theato, P., Sung, Y., Char, K., & Pyun, J. (2011). Elemental sulfur as a reactive medium for gold nanoparticles and nanocomposite materials. Angewandte Chemie (International ed. in English), 50(48), 11409-12.
• Glass, R. S., Schöneich, C., Wilson, G. S., Nauser, T., Yamamoto, T., Lorance, E., Nichol, G. S., & Ammam, M. (2011). Neighboring pyrrolidine amide participation in thioether oxidation. Methionine as a "hopping" site. Organic letters, 13(11), 2837-9.
  More info

  Methionine residues have been shown to function as efficient "hopping" sites in long-range electron transfer in model polyprolyl peptides. We suggest that a key to this ability of methionine is stabilization of the transient sulfur radical cation by neighboring proline amide participation. That is, in a model system a neighboring pyrrolidine amide lowers the oxidation potential of the thioether by over 0.5 V by formation of a two-center three-electron SO bond.
• Glass, R. S., Schöneich, C., Wilson, G. S., Nauser, T., Yamamoto, T., Lorance, E., Nichol, G. S., & Ammam, M. (2011). Neighboring pyrrolidine amide participation in thioether oxidation. methionine as a "hopping" site. Organic Letters, 13(11), 2837-2839.
  More info

  PMID: 21563771;Abstract: Methionine residues have been shown to function as efficient "hopping" sites in long-range electron transfer in model polyprolyl peptides. We suggest that a key to this ability of methionine is stabilization of the transient sulfur radical cation by neighboring proline amide participation. That is, in a model system a neighboring pyrrolidine amide lowers the oxidation potential of the thioether by over 0.5 V by formation of a two-center three-electron SO bond. © 2011 American Chemical Society.
• Hall, G. B., M., L., A., G., Wang, S., Evans, D. H., Glass, R. S., & Lichtenberger, D. L. (2011). Increased stability of (μ-1,3-propanedithiolato)-diironhexacarbonyl anion, and new electrocatalytic pathways for molecular hydrogen production. ACS National Meeting Book of Abstracts.
  More info

  Abstract: Inexpensive and efficient production of molecular hydrogen is crucial to a renewable energy economy. Hydrogen production catalyzed by [μ-1,3-C3H6S2]Fe2(CO)6 (1), and [μ-1,3-C3H4(1,3-CH3)2S2]Fe2(CO)6 (2), which have features similar to the active sites of [FeFe]hydrogenases, are being studied. The electronic structure of 2 is found to be very similar to that of the previously studied catalyst 1 as probed by photoelectron and infrared spectroscopies. However, reduction of 1 is largely irreversible on the cyclic voltammetry (CV) time scale and has been shown to form a dimer, whereas the reduction of 2 is reversible on the CV time scale. The catalyzed reduction of protons from weak acids with pKa values from 18 to 25 in acetonitrile has revealed new catalytic mechanisms occurring at significantly less negative reduction potentials than previously observed. Possible pathways of these new mechanisms are examined by density functional theory and simulation of the electrochemical data.
• M., L., Hall, G. B., V., N., Evans, D. H., Glass, R. S., & Lichtenberger, D. L. (2011). Electrochemical, structural and computational study of a diiron hydrogenase active site mimic for the catalytic production of hydrogen, [(μ-3,4-thiophenedithiolato)][Fe(CO)₃]₂. ACS National Meeting Book of Abstracts.
  More info

  Abstract: A new functional mimic, [(μ-3,4-thiophenedithiolato)][Fe(CO)3]2, 1, of [FeFe]hydrogenase was prepared and characterized including using photoelectron spectroscopy, electrochemistry, and DFT computations. 1 has a semi-reversible two-electron reduction at -1.3 V and catalyzes reduction of protons from weak acid to produce hydrogen in acetonitrile at -1.9 V vs Fc+/Fc. 1 features unique structural distortions in forming a rotated cation 2 as well as dianion 3. The behavior is compared and contrasted with that of the analogous [(μ-1,2-benzenedithiolato)][Fe(CO)3]2.
• Ammam, M., Zakai, U. I., Wilson, G. S., & Glass, R. S. (2010). Anodic oxidation of m-terphenyl thio-, selenoand telluroethers: Lowered oxidation potentials due to chalcogen⋯πinteraction. Pure and Applied Chemistry, 82(3), 555-563.
  More info

  Abstract: The electrochemistry of m-terphenylthio-, seleno-, and telluroethers was studied using cyclic voltammetry in acetonitrile. All of the compounds studied showed irreversible oxidations. The first oxidation potentials for the thio- and selenoethers are less positive than expected. This facilitation in oxidation is ascribed to through-space S⋯πand Se⋯πinteraction, respectively, on removal of an electron. No evidence for a comparable effect was found for the phenyltelluro-ethers studied. © 2010 IUPAC.
• Chen, J., Vannucci, A. K., Mebi, C. A., Okumura, N., Borowski, S. C., Swenson, M., Lockett, L. T., Evans, D. H., Glass, R. S., & Lichtenberger, D. L. (2010). Synthesis of diiron hydrogenase mimics bearing hydroquinone and related ligands. Electrochemical and computational studies of the mechanism of hydrogen production and the role of O-H⋯S hydrogen bonding. Organometallics, 29(21), 5330-5340.
  More info

  Abstract: A new synthetic method for annulating hydroquinones to Fe2S 2(CO)6 moieties is reported. Piperidine catalyzed a multistep reaction between Fe2(μ-SH)2(CO)6 and quinones to afford bridged adducts in 26-76% yields. The hydroquinone adducts undergo reversible two-electron reductions. In the presence of acetic acid, hydrogen is produced catalytically with these adducts at potentials more negative than that of the initial reversible reduction. Spectroscopic studies suggest the presence of intramolecular hydrogen bonding between the phenolic OH groups and the adjacent sulfur atoms. Computations, which are in good agreement with the electrochemical studies and spectroscopic data, indicate that the hydrogen bonding is most important in the reduced forms of the catalysts. This hydrogen bonding lowers the reduction potential for catalysis but also lowers the basicity and thereby the reactivity of the catalysts. © 2010 American Chemical Society.
• Evans, D. H., Gruhn, N. E., Jin, J., Bo, L. i., Lorance, E., Okumura, N., Macías-Ruvalcaba, N. A., Zakai, U. I., Zhang, S., Block, E., & Glass, R. S. (2010). Electrochemical and chemical oxidation of dithia-, diselena-, ditellura-, selenathia-, and tellurathiamesocycles and stability of the oxidized species. Journal of Organic Chemistry, 75(6), 1997-2009.
  More info

  PMID: 20180528;Abstract: "Chemical Equation Presented" The diverse electrochemical and chemical oxidations of dichalcogena-mesocycles are analyzed, broadening our understanding of the chemistry of the corresponding radical cations and dications. 1,5-Diselenocane and 1,5-dithiocane undergo reversible two-electron oxidation with inverted potentials analogous to 1,5-dithiocane. On the other hand, 1,5-selenathiocane and 1,5-tellurathiocane undergo one-electron oxidative dimerization. The X-ray crystal structures of the Se-Se dimer of the 1,5-selenathiocane one-electron oxidized product and the monomeric two-electron oxidized product (dication) of 1,5-tellurathiocane are reported. 1,5-Dithiocanes and 1,5-diselenocanes with group 14 atoms as ring members undergo irreversible oxidation, unlike the reversible two-electron oxidation of the corresponding silicon-containing 1,5-ditellurocanes. These results demonstrate the chemical consequences of the dication stabilities Te+-Te+ > Se+-Se+> S+-S+, as well as Se+-Se+ > Se+-S+ and Te +-Te+ > Te+-S+. © 2010 American Chemical Society.
• Glass, R., Evans, D. H., Gruhn, N. E., Jin, J., Li, B., Lorance, E., Okumura, N., Macías-Ruvalcaba, N. A., Zakai, U. I., Zhang, S., Block, E., & Glass, R. S. (2010). Electrochemical and chemical oxidation of dithia-, diselena-, ditellura-, selenathia-, and tellurathiamesocycles and stability of the oxidized species. The Journal of organic chemistry, 75(6).
  More info

  The diverse electrochemical and chemical oxidations of dichalcogena-mesocycles are analyzed, broadening our understanding of the chemistry of the corresponding radical cations and dications. 1,5-Diselenocane and 1,5-ditellurocane undergo reversible two-electron oxidation with inverted potentials analogous to 1,5-dithiocane. On the other hand, 1,5-selenathiocane and 1,5-tellurathiocane undergo one-electron oxidative dimerization. The X-ray crystal structures of the Se-Se dimer of the 1,5-selenathiocane one-electron oxidized product and the monomeric two-electron oxidized product (dication) of 1,5-tellurathiocane are reported. 1,5-Dithiocanes and 1,5-diselenocanes with group 14 atoms as ring members undergo irreversible oxidation, unlike the reversible two-electron oxidation of the corresponding silicon-containing 1,5-ditellurocanes. These results demonstrate the chemical consequences of the dication stabilities Te(+)-Te(+) > Se(+)-Se(+) > S(+)-S(+), as well as Se(+)-Se(+) > Se(+)-S(+) and Te(+)-Te(+) > Te(+)-S(+).
• Glass, R., Vannucci, A. K., Wang, S., Nichol, G. S., Lichtenberger, D. L., Evans, D. H., & Glass, R. S. (2010). Electronic and geometric effects of phosphatriazaadamantane ligands on the catalytic activity of an [FeFe] hydrogenase inspired complex. Dalton transactions (Cambridge, England : 2003), 39(12).
  More info

  The [FeFe] hydrogenase enzyme active site inspired complexes [Fe(2)(mu-C(6)H(4)S(2))(CO)(5)PTA] (1PTA) and [Fe(2)(mu-C(6)H(4)S(2))(CO)(4)PTA(2)] (1PTA(2)) (PTA = 1,3,5-triaza-7-phosphaadamantane) were synthesized and characterized. The ability of 1PTA and 1PTA(2) to catalytically produce molecular hydrogen in solution from the weak acid acetic acid was examined electrochemically and compared to previous studies on the all carbonyl containing analogue [Fe(2)(mu-C(6)H(4)S(2))(CO)(6)] (1). Computational methods and cyclic voltammograms indicated that the substitution of CO ligands by PTA in 1 resulted in markedly different reduction chemistry. Both 1PTA and 1PTA(2) catalytically produce molecular hydrogen from acetic acid, however, the mechanism by which and 1PTA and 1PTA(2) catalyze hydrogen differ in the initial reductive processes.
• Glass, R., Zakai, U. I., Błoch-Mechkour, A., Jacobsen, N. E., Abrell, L., Lin, G., Nichol, G. S., Bally, T., & Glass, R. S. (2010). Synthesis and structure of m-terphenyl thio-, seleno-, and telluroethers. The Journal of organic chemistry, 75(24).
  More info

  Several routes for the synthesis of m-terphenyl thio-, seleno-, and telluroethers were investigated. m-Terphenyl iodides react with diphenyl diselenides or ditellurides (CsOH·H(2)O, DMSO, 110 °C) to give the desired compounds in 19-84% yield which significantly extends the previously reported such reactions because o-benzyne cannot be an intermediate as previously suggested. However, the most general synthetic route was that involving reaction of 2,6-diaryl Grignard reagents with sulfur, selenium, or tellurium electrophiles. The m-terphenyl thio-, seleno-, and telluroethers were characterized spectroscopically and, in one case, by single-crystal X-ray analysis. Certain of these compounds showed atropisomerism and barriers for interconversion of isomers were determined by variable-temperature NMR spectroscopy. The barriers for interconverting the syn and anti atropisomers increase on going from the analogous S to Se to Te compounds. Calculations on this isomerization revealed that the barriers are due to rotation about the aryl-aryl bond and that the barriers for rotation about the aryl-chalcogen bond are much lower.
• Harb, M. K., Görls, H., Sakamoto, T., A., G., Evans, D. H., Glass, R. S., Lichtenberger, D. L., El-Khateeb, M., & Weigand, W. (2010). Synthesis and characterization of [FeFe]-hydrogenase models with bridging moieties containing (S, Se) and (S, Te) (European Journal of Inorganic Chemistry (2010) 3976-3985)). European Journal of Inorganic Chemistry, 4561-.
• Harb, M. K., Görls, H., Sakamoto, T., A., G., Evans, D. H., Glass, R. S., Lichtenberger, D. L., El-Khateeb, M., & Weigand, W. (2010). Synthesis and characterization of [FeFe]-hydrogenase models with bridging moieties containing (S, Se) and (S, Te). European Journal of Inorganic Chemistry, 3976-3985.
  More info

  Abstract: [FeFe]-hydrogenase-active-site models containing larger chalcogens such as Se or Te have exhibited greater electron richness at the metal centers and smaller gas-phase ionization energies and reorganization energies relative to molecules containing S atoms. Diiron complexes related to the much-studied molecule [Fe2(μ-SC3H6S)(CO)6] (1) have been prepared with one S atom replaced either by one Se atom to give [Fe2(μ-SC3H6Se)(CO)6] (2) or by one Te atom to give [Fe2(μ-SC3H6Te)(CO) 6] (3). The molecules have been characterized by use of mass spectrometry and 13C{1H} NMR, 77Se{ 1H} NMR, IR, and photoelectron spectroscopic techniques along with structure determination with single-crystal X-ray diffraction, electrochemical measurements, and DFT calculations. He I photoelectron spectra and DFT computations of 2 and 3 show a lowering of ionization energies relative to those of the all-sulfur complex 1, indicating increased electron richness at the metal centers that favors electrocatalytic reduction of protons from weak acids to produce H2. However, chalcogen substitution from S to Se or Te also causes an increase in the Fe-Fe bond length, which disfavors the formation of a carbonyl-bridged "rotated" structure, as also shown by the photoelectron spectra and computations. This "rotated" structure is believed to be important in the mechanism of H2 production. As a consequence of the competing influences of increased electron richness at the metals with less favorable "rotated" structures, the catalytic efficiency of the Se and Te molecules 2 and 3 is found to be comparable to that of molecule 1. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
• Vannucci, A. K., Wang, S., Nichol, G. S., Lichtenberger, D. L., Evans, D. H., & Glass, R. S. (2010). Electronic and geometric effects of phosphatriazaadamantane ligands on the catalytic activity of an [FeFe] hydrogenase inspired complex. Dalton Transactions, 39(12), 3050-3056.
  More info

  PMID: 20221539;Abstract: The [FeFe] hydrogenase enzyme active site inspired complexes [Fe 2(μ-C6H4S2)(CO)5PTA] (1PTA) and [Fe2(μ-C6H4S2)(CO) 4PTA2] (1PTA2) (PTA = 1,3,5-triaza-7- phosphaadamantane) were synthesized and characterized. The ability of 1PTA and 1PTA2 to catalytically produce molecular hydrogen in solution from the weak acid acetic acid was examined electrochemically and compared to previous studies on the all carbonyl containing analogue [Fe2(μ- C6H4S2)(CO)6] (1). Computational methods and cyclic voltammograms indicated that the substitution of CO ligands by PTA in 1 resulted in markedly different reduction chemistry. Both 1PTA and 1PTA2 catalytically produce molecular hydrogen from acetic acid, however, the mechanism by which 1 and 1PTA and 1PTA2 catalyze hydrogen differ in the initial reductive processes. © 2010 The Royal Society of Chemistry.
• Zakai, U. I., Błoch-Mechkour, A., Jacobsen, N. E., Abrell, L., Lin, G., Nichol, G. S., Bally, T., & Glass, R. S. (2010). Synthesis and structure of m-terphenyl thio-, seleno-, and telluroethers. Journal of Organic Chemistry, 75(24), 8363-8371.
  More info

  PMID: 21080662;Abstract: Several routes for the synthesis of m-terphenyl thio-, seleno-, and telluroethers were investigated. m-Terphenyl iodides react with diphenyl diselenides or ditellurides (CsOH·H2O, DMSO, 110 °C) to give the desired compounds in 19-84% yield which significantly extends the previously reported such reactions because o-benzyne cannot be an intermediate as previously suggested. However, the most general synthetic route was that involving reaction of 2,6-diaryl Grignard reagents with sulfur, selenium, or tellurium electrophiles. The m-terphenyl thio-, seleno-, and telluroethers were characterized spectroscopically and, in one case, by single-crystal X-ray analysis. Certain of these compounds showed atropisomerism and barriers for interconversion of isomers were determined by variable-temperature NMR spectroscopy. The barriers for interconverting the syn and anti atropisomers increase on going from the analogous S to Se to Te compounds. Calculations on this isomerization revealed that the barriers are due to rotation about the aryl-aryl bond and that the barriers for rotation about the aryl-chalcogen bond are much lower. © 2010 American Chemical Society.
• A., G., Petro, B. J., Glass, R. S., Lichtenberger, D. L., & Evans, D. H. (2009). One- to two-electron reduction of an [FeFe]-hydrogenase active site mimic: The critical role of fluxionality of the [2Fe2S] core. Journal of the American Chemical Society, 131(32), 11290-11291.
  More info

  PMID: 19630410;Abstract: (Figure Presented) The one- to two-electron reduction of μ-(1,2-ethanedithiolato)diironhexacarbonyl that has been observed under electrochemical conditions is dependent on scan rate and temperature, suggesting activation of a structural rearrangement. This structural rearrangement is attributed to fluxionality of the [2Fe2S] core in the initially formed anion. Computations support this assessment. Upon an initial one-electron reduction, the inherent fluxionality of the [2Fe2S] complex anion allows for a second one-electron reduction at a less negative potential to form a dianionic species. The structure of this dianion is characterized by a rotated iron center, a bridging carbonyl ligand, and, most significantly, a dissociated Fe-S bond. This fluxionality of the [2Fe2S] core upon reduction has direct implications for the chemistry of [FeFe]-hydrogenase mimics and for iron-sulfur cluster chemistry in general. © 2009 American Chemical Society.
• Chung, W. J., Ammam, M., Gruhn, N. E., Nichol, G. S., Singh, W. P., Wilson, G. S., & Glass, R. S. (2009). Interactions of arenes and thioethers resulting in facilitated oxidation. Organic Letters, 11(2), 397-400.
  More info

  PMID: 19102660;Abstract: (Figure Presented) Synthesis of 6-endo and 6-exomethylthio-2- endoarylbicyclo[2.2.1]heptanes was accomplished stereoselectively. The ionization energies, determined by photoelectron spectroscopy, and electrochemical oxidation potentials, determined by cyclic voltammetry, were lower for the 6-endomethylthio compounds than for their 6-exomethylthio analogues. Calculations supported the notion that facilitation of electron transfer in the 6-endomethylthio compounds results from through-space S⋯π interaction. © 2009 American Chemical Society.
• Felton, G. A., Mebi, C. A., Petro, B. J., Vannucci, A. K., Evans, D. H., Glass, R. S., & Lichtenberger, D. L. (2009). Review of electrochemical studies of complexes containing the Fe₂S₂ core characteristic of [FeFe]-hydrogenases including catalysis by these complexes of the reduction of acids to form dihydrogen. Journal of Organometallic Chemistry, 694(17), 2681-2699.
  More info

  Abstract: This article reviews published literature on the electrochemical reduction and oxidation of complexes containing the Fe2S2 core characteristic of the active site of [FeFe]-hydrogenases. Correlations between reduction and oxidation potentials and molecular structure are developed and presented. In cases where the complexes have been studied with regard to their ability to catalyze the reduction of acids to give dihydrogen, the overpotentials for such catalyzed reduction are presented and an attempt is made to estimate, at least qualitatively, the efficiency of such catalysis. © 2009 Elsevier B.V. All rights reserved.
• Felton, G. A., Petro, B. J., Glass, R. S., Lichtenberger, D. L., & Evans, D. H. (2009). One- to two-electron reduction of an [FeFe]-hydrogenase active site mimic: the critical role of fluxionality of the [2Fe2S] core. Journal of the American Chemical Society, 131(32), 11290-1.
  More info

  The one- to two-electron reduction of mu-(1,2-ethanedithiolato)diironhexacarbonyl that has been observed under electrochemical conditions is dependent on scan rate and temperature, suggesting activation of a structural rearrangement. This structural rearrangement is attributed to fluxionality of the [2Fe2S] core in the initially formed anion. Computations support this assessment. Upon an initial one-electron reduction, the inherent fluxionality of the [2Fe2S] complex anion allows for a second one-electron reduction at a less negative potential to form a dianionic species. The structure of this dianion is characterized by a rotated iron center, a bridging carbonyl ligand, and, most significantly, a dissociated Fe-S bond. This fluxionality of the [2Fe2S] core upon reduction has direct implications for the chemistry of [FeFe]-hydrogenase mimics and for iron-sulfur cluster chemistry in general.
• Glass, R. S., Hug, G. L., Schöneich, C., Wilson, G. S., Kuznetsova, L., Lee, T., Ammam, M., Lorance, E., Nauser, T., Nichol, G. S., & Yamamoto, T. (2009). Neighboring amide participation in thioether oxidation: Relevance to biological oxidation. Journal of the American Chemical Society, 131(38), 13791-13805.
  More info

  PMID: 19772365;Abstract: To investigate neighboring amide participation in thioether oxidation, which may be relevant to brain oxidative stress accompanying β-amyloid peptide aggregation, conformationally constrained methylthionorbornyl derivatives with amido moieties were synthesized and characterized, including an X-ray crystallographic study of one of them. Electrochemical oxidation of these compounds, studied by cyclic voltammetry, revealed that their oxidation peak potentials were less positive for those compounds in which neighboring group participation was geometrically possible. Pulse radiolysis studies provided evidence for bond formation between the amide moiety and sulfur on one-electron oxidation in cases where the moieties are juxtaposed. Furthermore, molecular constraints in spiro analogues revealed that S-O bonds are formed on one-electron oxidation. DFT calculations suggest that isomeric σ*SO radicals are formed in these systems. © 2009 American Chemical Society.
• Glass, R. S., Hug, G. L., Schöneich, C., Wilson, G. S., Kuznetsova, L., Lee, T., Ammam, M., Lorance, E., Nauser, T., Nichol, G. S., & Yamamoto, T. (2009). Neighboring amide participation in thioether oxidation: relevance to biological oxidation. Journal of the American Chemical Society, 131(38), 13791-805.
  More info

  To investigate neighboring amide participation in thioether oxidation, which may be relevant to brain oxidative stress accompanying beta-amyloid peptide aggregation, conformationally constrained methylthionorbornyl derivatives with amido moieties were synthesized and characterized, including an X-ray crystallographic study of one of them. Electrochemical oxidation of these compounds, studied by cyclic voltammetry, revealed that their oxidation peak potentials were less positive for those compounds in which neighboring group participation was geometrically possible. Pulse radiolysis studies provided evidence for bond formation between the amide moiety and sulfur on one-electron oxidation in cases where the moieties are juxtaposed. Furthermore, molecular constraints in spiro analogues revealed that S-O bonds are formed on one-electron oxidation. DFT calculations suggest that isomeric sigma*(SO) radicals are formed in these systems.
• Glass, R., Chung, W. J., Ammam, M., Gruhn, N. E., Nichol, G. S., Singh, W. P., Wilson, G. S., & Glass, R. S. (2009). Interactions of arenes and thioethers resulting in facilitated oxidation. Organic letters, 11(2).
  More info

  Synthesis of 6-endo and 6-exomethylthio-2-endoarylbicyclo[2.2.1]heptanes was accomplished stereoselectively. The ionization energies, determined by photoelectron spectroscopy, and electrochemical oxidation potentials, determined by cyclic voltammetry, were lower for the 6-endomethylthio compounds than for their 6-exomethylthio analogues. Calculations supported the notion that facilitation of electron transfer in the 6-endomethylthio compounds results from through-space S...pi interaction.
• Harb, M. K., Apfel, U., Kübel, J., Görls, H., Feiton, G. A., Sakamoto, T., Evans, D. H., Glass, R. S., Lichtenberger, D. L., El-khateeb, M., & Weigand, W. (2009). Preparation and characterization of homologous diiron dithiolato, diselenato, and ditellurato complexes: [FeFe]-hydrogenase models. Organometallics, 28(23), 6666-6675.
  More info

  Abstract: In order to elucidate the influence of the bridging chalcogen atoms in hydrogenase model complexes, diiron dithiolato, diselenolato, and ditellurolato complexes have been prepared and characterized. Treatment of Fe 3(CO)12 with 3,3-bis(thiocyanatomethyl)oxetane (1) or a mixture of 2-oxa-6,7-dithiaspiro[3.4]octane (2a) and 2-oxa-6,7,8-trithiaspiro[3. 5]nonane (2b) in toluene at reflux afforded the model compound Fe 2(μ-S2C5H8O)(CO)6 (3). The analogous diselenolato and ditellurolato complexes, Fe2(μ- Se2C5H8O)(CO)6 (4) and Fe 2(μ-Te2C5H8O)(CO)6 (5), were obtained from the reaction of Fe3(CO)12 with 2-oxa-6,7-diselenaspiro[3.4]octane (6) and 2-oxa-6,7-ditelluraspiro[3.4]octane (7), respectively. Compounds 3-5 were characterized by spectroscopic techniques (NMR, IR, photoelectron spectroscopy), mass spectrometry, single-crystal X-ray analysis, and computational modeling. The electrochemical properties for the new compounds have been studied to assess their ability to catalyze electrochemical reduction of protons to give dihydrogen, and the catalytic rate is found to decrease on going from the sulfur to selenium to tellurium compounds. In the series 3-5 the reorganization energy on going to the corresponding cation decreased from 3 to 4 to 5. Spectroscopic and computational analysis suggests that the increasing size of the chalcogen atoms from S to Se to Te increases the Fe-Fe distance and decreases the ability of the complex to form the structure with a rotated Fe(CO)3 group that has a bridging carbonyl ligand and a vacant coordination site for protonation. This effect is mirrored on reduction of 3-5 in that the rotated structure with a bridging carbonyl, which creates a vacant coordination site for protonation, is disfavored on going from the S to Se to Te complexes. © 2009 American Chemical Society.
• Harb, M. K., Niksch, T., Windhager, J., Görls, H., Holze, R., Lockett, L. T., Okumura, N., Evans, D. H., Glass, R. S., Lichtenberger, D. L., El-khateeb, M., & Weigand, W. (2009). Synthesis and characterization of diiron diselenolato complexes including Iron Hydrogenase models. Organometallics, 28(4), 1039-1048.
  More info

  Abstract: Diiron diselenolato complexes have been prepared as models of the active site of [FeFe]-hydrogenases. Treatment of Fe 3(CO) 12 with 1 equiv of 1,3-diselenocyanatopropane (1) in THF at reflux afforded the model compound Fe 2(μ-Se 2C 3H 6)(CO) 6 (2) in 68% yield. The analogous methyl-substituted complex, Fe 2(μ-Se 2C 3H 5CH3)(CO) 6 (3), was obtained from the reaction of Fe 3(CO) 12 with the in situ generated compound 3-methyl-1,2-diselenolane (4). In contrast, the reaction of Fe 3(CO) 12 with 1,3,5-triselenacy-clohexane (5) produced a mixture of Fe 2(μ 2,k-Se,C-SeCH 2SeCH 2)(CO) 6 (6), Fe 2[(μ- SeCH 2) 2Se](CO) 6 (7), and Fe 2(μ- Se 2CH 2)(CO) 6 (8). Compounds 2, 3, 6, and 7 were characterized by IR, 1H, 13C, and 77Se NMR spectroscopy, mass spectrometry, elemental analysis, and X-ray single-crystal structure analysis. The He I and He II photoelectron spectra for 3 are reported, and the electronic structure is further analyzed with the aid of DFT computations. The calculated reorganization energy of the cation of 3 to the "rotated" structure, which has a semibridging carbonyl ligand, is less than that of the analogous complexes with sulfur instead of selenium. Complexes 2 and 3 have been proved to be catalysts for electrochemical reduction of protons from the weak acids pivalic and acetic acid, respectively, to give hydrogen. © 2009 American Chemical Society.
• Harb, M. K., Windhager, J., Ahmad, D., Görls, H., Lockett, L., Okumura, N., Evans, D. H., Glass, R. S., Lichtenberger, D. L., El-khateeb, M., & Weigand, W. (2009). Phosphane- and phosphite-substituted diiron diselenolato complexes as models for [FeFe]-hydrogenases. European Journal of Inorganic Chemistry, 3414-3420.
  More info

  Abstract: The displacement of terminal CO ligands in Fe2(μSe 2C3H5CH3)(CO)6 (1) by triphenylphosphane, trimethyl phosphite, and bis(diphenylphosphanyl)ethane (dppe) li:jands is investigated. Treatment of 1 with 1. equiv. of triphenylphosphane afforded Fe2(μ-Se2C3H 5CH3)(CO)5(PPh3) (2). The mono- and disubstituted phosphite complexes Fe2(μSe2C 3H5CH3)(CO)5P(OMe)3(3) and Fe2(μ-Se2C3H5CH 3)(CO)4-[P(OMe)3]2 (4) were obtained from the reaction of 1 with excess P(OMe)3 at reflux in toluene. In contrast, the reaction of 1 with 1 equiv. of dppe in the presence of Me 3NO-2H2O gave a mixture of Fe2(μ-Se 2C3H5CH3)(CO)4(κ 2-dppe) (5) and [Fe2(μ-Se2C 3H5CH3)(CO)5]2(μ-dppe) (6). The newly synthesized complexes 2-6 were fully characterized by IR, 1H NMR, 13C NMR, 77Se{1H} NMR, and 31P{1H} NMR spectroscopy, mass spectrometry, elemental analysis, and X-ray diffraction analysis. Complex 2 has proved to be a catalyst for the electrochemical reduction of the weak acid, acetic acid, to give molecular hydrogen. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.
• Naumov, S., Bonifačić, M., Glass, R. S., & Asmus, K. (2009). Theoretical calculations and experimental data on spectral, kinetic and thermodynamic properties of Se;N and S;N three-electron-bonded, structurally stabilized σ²σ* radicals. Research on Chemical Intermediates, 35(4), 479-496.
  More info

  Abstract: A complementary quantum mechanical and experimental study has been undertaken on the reactivity, formation and properties of Se;N and S;N σ2/σ* three-electron-bonded radical species, generated upon one-electron oxidation of selenomethionine, methionine and structurally related compounds. The quantum chemical calculations were based on density functional theory (DFT) hybrid B3LYP and BHandHLYP methods with basis sets ranging from 6-31G(d) to 6-311+G(d,p). Solvent effects, which play an important role concerning structure and energy of ground and excited states, were taken into account as dielectric continuum as well as explicit water molecules. They fully confirm new and previously obtained experimental results concerning the Vis/near-UV absorptions and thermodynamic stability. Special emphasis was put on a comparison between selenium and sulfur. The calculations clearly confirm the higher thermodynamic stability of the Se;N radical species relative to the S;N ones, and also corroborate the observed much higher kinetic stability of the former. Concerning optical absorptions, the calculations predict the Se;N transients to exhibit a blue-shift by about 20 nm relative to the S-based analogues, confirming the few experimental data available so far. The theoretical study includes a comparison of various calculation levels and the influence of the solvent environment, by comparison with vacuum. New experimental data within the scope of this study have been obtained on intramolecularlyformed S;N radical cation moieties, structurally stabilized by a rigid norbornane backbone. The methionine-related species, with an endo-2-amino, exo-2-carboxyl,and endo-6 methylthio substitution, for example, exhibits almost identical optical and kinetic stability properties as the corresponding species from free methionine. Its optical absorption depends on the protonation state of the carboxyl group, with λmax at 410 nm for the carboxylate (zwitterionic) form and at 390 nm for the overall cationicform with the protonated carboxyl group. The fast exponential decays with t1/2 of 490 ns and 2 mu;s pertain to the decarboxylation of the respective species. A much longer-lived S;N species with t1/2>500 ls and second order decay kinetics (λmax 465 nm) was obtained from an endo-2-cyclohexylamino norbornane analogue which does not carry a carboxyl group. The methionine-based S;N species is not stable anymore in vacuum and in low polarity solvents. This is explained by a decrease in stabilization energy of the 3-e-bond and a faster electron transfer from the carboxylate into the cationic 3-e-center. In conclusion, seleniumenhances the thermodynamic and kinetic stability of its radical transients, relative to the sulfur analogues. © Springer Science+Business Media BV 2009.
• Velarde, L., Habteyes, T., Glass, R. S., & Sanov, A. (2009). Observation and characterization of the CH ₃S(O)CH ^- and CH ₃S(O)CH ^-· H ₂O carbene anions by photoelectron imaging and photofragment spectroscopy. Journal of Physical Chemistry A, 113(15), 3528-3534.
  More info

  PMID: 19309097;Abstract: We report the observation of the CH 3S(O)CH - and CH 3S(O)CH -·H 2O carbene anions formed upon overall H 2+ abstraction from dimethyl sulfoxide by O -. Photoelectron spectroscopy reveals singlet and triplet carbenes for the remaining neutral, with the singlet state assigned as the ground state. Although some formation of the distonic CH 2S(O)CH 2- radical anion is also expected, no conclusive evidence of the presence of this isomer is found. The photoelectron spectrum of HCSO - is also reported for the first time. Photofragmentation of CH 3S(O)CH - with 532 nm light reveals two main types of anionic products: a dominant HCSO - fragment, resulting from methyl elimination, and a less intense SO - product. For the monohydrated anion, an additional SO - · H 2O fragment is observed. Intriguingly, both the SO -·H 2O and SO - products are produced with much higher yields in the fragmentation of CH 3S(O)CH - · H 2O, compared to the SO - yield from the dissociation of the bare CH 3S(O)CH- anion. Two possible pathways are proposed as likely mechanisms for the SO --based photoproducts, both involving a photoinduced intramolecular rearrangement and the formation of a C-C bond. © 2009 American Chemical Society.
• Velarde, L., Habteyes, T., Glass, R. S., & Sanov, A. (2009). Observation and characterization of the CH3S(O)CH- and CH3S(O)CH- x H2O carbene anions by photoelectron imaging and photofragment spectroscopy. The journal of physical chemistry. A, 113(15), 3528-34.
  More info

  We report the observation of the CH(3)S(O)CH(-) and CH(3)S(O)CH(-) x H(2)O carbene anions formed upon overall H(2)(+) abstraction from dimethyl sulfoxide by O(-). Photoelectron spectroscopy reveals singlet and triplet carbenes for the remaining neutral, with the singlet state assigned as the ground state. Although some formation of the distonic CH(2)S(O)CH(2)(-) radical anion is also expected, no conclusive evidence of the presence of this isomer is found. The photoelectron spectrum of HCSO(-) is also reported for the first time. Photofragmentation of CH(3)S(O)CH(-) with 532 nm light reveals two main types of anionic products: a dominant HCSO(-) fragment, resulting from methyl elimination, and a less intense SO(-) product. For the monohydrated anion, an additional SO(-) x H(2)O fragment is observed. Intriguingly, both the SO(-) x H(2)O and SO(-) products are produced with much higher yields in the fragmentation of CH(3)S(O)CH(-) x H(2)O, compared to the SO(-) yield from the dissociation of the bare CH(3)S(O)CH(-) anion. Two possible pathways are proposed as likely mechanisms for the SO(-)-based photoproducts, both involving a photoinduced intramolecular rearrangement and the formation of a C-C bond.
• A., G., Vannucci, A. K., Okumura, N., Lockett, L. T., Evans, D. H., Glass, R. S., & Lichtenberger, D. L. (2008). Hydrogen generation from weak acids: electrochemical and computational studies in the [(η⁵-C₅H₅)Fe(CO) ₂]₂ system. Organometallics, 27(18), 4671-4679.
  More info

  Abstract: (η5-C5H5)Fe(CO)2H (FpH) is stable to weak acids such as acetic acid. However, reduction of FpH in acetonitrile in the presence of weak acids generates H2 catalytically. Evidence for the catalytic generation of H2 from just water also is observed. Since reduction of Fp2 generates Fp -, which can be protonated with weak acids, Fp2 serves as a convenient procatalyst for the electrocatalytic production of H2. Electrochemical simulations provide values for the key parameters of a catalytic mechanism for production of H2 in this system. Protonation of Fp- is found to be the rate-determining step preceding H2 production. The wealth of structural, spectroscopic, and thermodynamic information available on the key Fp2, Fp-, and FpH species provide a variety of checkpoints for computational modeling of the catalytic mechanism. The computations give good agreement with the crystal structure of Fp2, the IR spectra of Fp2, Fp-, and FpH, and the photoelectron spectra of Fp2 and FpH. The computations also account well for the reduction potentials and equilibrium constants in the electrochemical simulations. The FpH- anion is found to be susceptible to a direct and rapid attack by a proton to produce H2 and the Fp radical, which is then reduced and protonated to continue the electrocatalytic cycle. This direct energetically downhill step of metal hydride protonation to produce molecular hydrogen may be common for sufficiently electron rich metal hydrides and/or sufficiently strong acids among many of the hydrogenase mimics reported thus far. © 2008 American Chemical Society.
• Block, E., Glass, R. S., Gruhn, N., Jin, J., Lorance, E., Zakai, U. I., & Zhang, S. (2008). Chemistry of mixed sulfur-, selenium-, or tellurium- and silicon-, or tin-containing heterocycles. Phosphorus, Sulfur and Silicon and the Related Elements, 183(4), 856-862.
  More info

  Abstract: Lone pair ionization energies for 1,5-dichalcogenocanes containing endocyclic 3,7-R2Si groups and the parent 1,5-dichalcogenocanes, estimated from the TCNE charge-transfer wavelength maxima, are in good agreement with ionization energies directly obtained from photoelectron spectroscopy. These data indicate the occurrence of substantial intra-annular interaction between the chalcogen atoms and silyl groups, consistent with the well-known β-effect of silicon and the novel β-disilyl effect, when R (in R 2Si) is Me3Si.
• Glass, R. S., Berry, M. J., Block, E., Boakye, H. T., Carlson, B. A., Gailer, J., George, G. N., Gladyshev, V. N., Hatfield, D. L., Jacobsen, N. E., Johnson, S., Kahakachchi, C., Kaminski, R., Manley, S. A., Mix, H., Pickering, I. J., Prenner, E. J., Saira, K., Skowronska, A., , Tyson, J. F., et al. (2008). Insights into the chemical biology of selenium. Phosphorus, Sulfur and Silicon and the Related Elements, 183(4), 924-930.
  More info

  Abstract: The long-sought pathway by which selenocysteyl-tRNA[Ser]Sec is synthesized in eukaryotes has been revealed. Seryl-tRNA[Ser]Sec is O-phosphorylated and SecS, a pyridoxal phosphate-dependent protein, catalyzes the reaction of O-phosphoseryl-tRNA[Ser]Sec with monoselenophosphate to give selenocysteyl-tRNA[Ser]Sec. 1H-77Se HMQC-TOCSY NMR spectroscopy has been developed to detect the selenium-containing amino acids present in selenized yeast after protease XIV digestion. An archived selenized yeast sample is found to contain the novel amino acid S-(methylseleno)cysteine in addition to selenomethionine. Arsenite and selenite react with GSH to form (GS)2AsSe-. The structure of this compound has been determined by EXAFS, 77Se NMR and Raman spectroscopic and chromatographic studies. Its formation under biological conditions has been demonstrated.
• Petro, B. J., Vannucci, A. K., Lockett, L. T., Mebi, C., Kottani, R., Gruhn, N. E., Nichol, G. S., Goodyer, P. A., Evans, D. H., Glass, R. S., & Lichtenberger, D. L. (2008). Photoelectron spectroscopy of dithiolatodiironhexacarbonyl models for the active site of [Fe-Fe] hydrogenases: Insight into the reorganization energy of the "rotated" structure in the enzyme. Journal of Molecular Structure, 890(1-3), 281-288.
  More info

  Abstract: Synthetic analogs, μ-(RS)2Fe2(CO)6, of the active site of [Fe-Fe] hydrogenases do not have the semi-bridged CO and "rotated" structure found in the enzyme. However, recent studies have shown that cations of dithiolatodiiron complexes adopt this rotated structure. This paper reports the use of photoelectron spectroscopy in combination with density functional theory calculations to show that two previously reported complexes: μ-(1,2-benzenedithiolato)Fe2(CO)6 and μ-(1,3-propanedithiolato)Fe2(CO)6 and two new complexes: μ-(2,3-pyridinodithiolato)Fe2(CO)6 and μ-(norbornane-2-exo,3-exo-dithiolato)Fe2(CO)6 favor the "rotated" structure in their corresponding cations. Furthermore, these methods provide a measure of the reorganization energy between the "rotated" and "unrotated" structures in the gas phase. The results provide insight on the entatic state of the dithiolatodiiron site in the enzyme, in which the protein controls the structure of the active site. This structure influences the redox energy and reorganization energy enabling fast electron transfer. © 2008.
• A., G., Glass, R. S., Lichtenberger, D. L., & Evans, D. H. (2007). Erratum: Iron-only hydrogenase mimics. Thermodynamic aspects of the use of electrochemistry to evaluate catalytic efficiency for hydrogen generation (Inorganic Chemistry (2005) 44). Inorganic Chemistry, 46(12), 5126-.
• A., G., Glass, R. S., Lichtenberger, D. L., & Evans, D. H. (2007). Erratum: Iron-only hydrogenase mimics. Thermodynamic aspects of the use of electrochemistry to evaluate catalytic efficiency for hydrogen generation (Inorganic Chemistry (2006) 45, (5126)). Inorganic Chemistry, 46(19), 8098-.
• A., G., Vannucci, A. K., Chen, J., Lockett, L. T., Okumura, N., Petro, B. J., Zakai, U. I., Evans, D. H., Glass, R. S., & Lichtenberger, D. L. (2007). Hydrogen generation from weak acids: Electrochemical and computational studies of a diiron hydrogenase mimic. Journal of the American Chemical Society, 129(41), 12521-12530.
  More info

  PMID: 17894491;Abstract: Extended investigation of electrocatalytic generation of dihydrogen using [(μ-1,2-benzenedithiolato)][Fe(CO)3]2 has revealed that weak acids, such as acetic acid, can be used. The catalytic reduction producing dihydrogen occurs at approximately -2 V for several carboxylic acids and phenols resulting in overpotentials of only -0.44 to -0.71 V depending on the weak acid used. This unusual catalytic reduction occurs at a potential at which the starting material, in the absence of a proton source, does not show a reduction peak. The mechanism for this process and structures for the intermediates have been discerned by electrochemical and computational analysis. These studies reveal that the catalyst is the monoanion of the starting material and an ECEC mechanism occurs. © 2007 American Chemical Society.
• Block, E., Glass, R. S., Dikarev, E. V., Gruhn, N. E., Jin, J., Bo, L. i., Lorance, E., Zakai, U. I., & Zhang, S. (2007). Synthesis, structure, reactions, and photoelectron spectra of new mixed sulfur-, selenium- Or tellurium and silicon- Or tin-containing heterocycles. Heteroatom Chemistry, 18(5), 509-515.
  More info

  Abstract: More than 40 new 4- to 12-membered ring heterocycles containing various combinations of Group 14 elements (Si and Sn) and Group 16 elements (S, Se, and Te) have been synthesized and fully characterized. Synthesis of these small-ring as well as medium-ring (mesocyclic) heterocycles from αa, ω-dihalides was facilitated by the presence of gemdialkylsilyl and gem-dialkylstannyl groups in the precursors. Solid-state conformations of the new ring systems have been determined by X-ray crystallography. Oxidation of mixed S(Se, Te)/Si eight-membered ring mesocycles as well as 1,5-dithia-, 1,5-diselena-, and 1,5-ditelluracyclooctane with NOPF6 gave dications, which can be characterized by NMR. On treatment with nucleophiles, mesocyclic dications or the corresponding radical cations underwent ring contraction to give five- or six-membered ring heterocycles. The ionization energies of the above conformationally constrained β-disilanyl sulfides and selenides were determined by photoelectron spectroscopy. These ionization energies reflect substantial (0.53-0.75 eV) orbital destabilizations. The basis for these destabilizations was investigated by theoretical calculations, which reveal geometry-dependent interaction between sulfur or selenium lone pair orbitais and σ-orbitals, especially Si - Si σ-orbitals. These results suggest facile redox chemistry for these compounds and significantly extend the concept of σ-stabilization of electron-deficient centers. © 2007 Wiley Periodicals, Inc.
• Felton, G. A., Vannucci, A. K., Chen, J., Lockett, L. T., Okumura, N., Petro, B. J., Zakai, U. I., Evans, D. H., Glass, R. S., & Lichtenberger, D. L. (2007). Hydrogen generation from weak acids: electrochemical and computational studies of a diiron hydrogenase mimic. Journal of the American Chemical Society, 129(41), 12521-30.
  More info

  Extended investigation of electrocatalytic generation of dihydrogen using [(mu-1,2-benzenedithiolato)][Fe(CO)3]2 has revealed that weak acids, such as acetic acid, can be used. The catalytic reduction producing dihydrogen occurs at approximately -2 V for several carboxylic acids and phenols resulting in overpotentials of only -0.44 to -0.71 V depending on the weak acid used. This unusual catalytic reduction occurs at a potential at which the starting material, in the absence of a proton source, does not show a reduction peak. The mechanism for this process and structures for the intermediates have been discerned by electrochemical and computational analysis. These studies reveal that the catalyst is the monoanion of the starting material and an ECEC mechanism occurs.
• Glass, R. S., Block, E., Gruhn, N. E., Jin, J., Lorance, E., Zakai, U. I., & Zhang, S. (2007). Interaction of C-Si, C-Sn, and Si-Si sigma-bonds with chalcogen lone pairs. The Journal of organic chemistry, 72(22), 8290-7.
  More info

  The ability of neighboring C-Si, C-Sn, and Si-Si groups in conformationally constrained cyclic molecules to reduce the lowest ionization energies of sulfur, selenium, and tellurium compounds has been determined by charge-transfer spectroscopy of complexes with tetracyanoethylene. For selected compounds, ionization energies were determined by gas-phase photoelectron spectroscopy. The lowest ionization energies measured by photoelectron spectroscopy, with one exception, correlate with the charge-transfer spectroscopic data. In addition, theoretical analysis has provided insight into the photoelectron spectra and the geometry-dependent interaction between C-Si or C-Sn bonds and chalcogen lone pairs. Substantial lowering of ionization energies is found which is anticipated to have important consequences in the chemistry of these and related species.
• Glass, R. S., Block, E., Gruhn, N. E., Jin, J., Lorance, E., Zakai, U. I., & Zhang, S. (2007). Interaction of C-Si, C-Sn, and Si-Si σ-bonds with chalcogen lone pairs. Journal of Organic Chemistry, 72(22), 8290-8297.
  More info

  PMID: 17915922;Abstract: (Figure Presented) The ability of neighboring C-Si, C-Sn, and Si-Si groups in conformationally constrained cyclic molecules to reduce the lowest ionization energies of sulfur, selenium, and tellurium compounds has been determined by charge-transfer spectroscopy of complexes with tetracyanoethylene. For selected compounds, ionization energies were determined by gas-phase photoelectron spectroscopy. The lowest ionization energies measured by photoelectron spectroscopy, with one exception, correlate with the charge-transfer spectroscopic data. In addition, theoretical analysis has provided insight into the photoelectron spectra and the geometry-dependent interaction between C-Si or C-Sn bonds and chalcogen lone pairs. Substantial lowering of ionization energies is found which is anticipated to have important consequences in the chemistry of these and related species. © 2007 American Chemical Society.
• Glass, R. S., Gruhn, N. E., Lorance, E., Singh, M. S., Y., N., & Zakai, U. I. (2007). Erratum: Synthesis, gas-phase photoelectron spectroscopic, and theoretical studies of stannylated dinuclear iron dithiolates (Inorganic Chemistry (2005) 44, (5735)). Inorganic Chemistry, 46(19), 8098-.
• Xu, X., Carlson, B. A., Mix, H., Zhang, Y., Saira, K., Glass, R. S., Berry, M. J., Gladyshev, V. N., & Hatfield, D. L. (2007). Biosynthesis of selenocysteine on its tRNA in eukaryotes. PLoS Biology, 5(1), 0096-0105.
  More info

  Abstract: Selenocysteine (Sec) is cotranslationally inserted into protein in response to UGA codons and is the 21st amino acid in the genetic code. However, the means by which Sec is synthesized in eukaryotes is not known. Herein, comparative genomics and experimental analyses revealed that the mammalian Sec synthase (SecS) is the previously identified pyridoxal phosphate-containing protein known as the soluble liver antigen. SecS required selenophosphate and O-phosphoseryl-tRNA[Ser]Sec as substrates to generate selenocysteyl-tRNA[Ser]Sec. Moreover, it was found that Sec was synthesized on the tRNA scaffold from selenide, ATP, and serine using tRNA [Ser]Sec, seryl-tRNA synthetase, O-phosphoseryl-tRNA [Ser]Sec kinase, selenophosphate synthetase, and SecS. By identifying the pathway of Sec biosynthesis in mammals, this study not only functionally characterized SecS but also assigned the function of the O-phosphoseryl- tRNA[Ser]Sec kinase. In addition, we found that selenophosphate synthetase 2 could synthesize monoselenophosphate in vitro but selenophosphate synthetase 1 could not. Conservation of the overall pathway of Sec biosynthesis suggests that this pathway is also active in other eukaryotes and archaea that synthesize selenoproteins.
• Xu, X., Carlson, B. A., Mix, H., Zhang, Y., Saira, K., Glass, R. S., Berry, M. J., Gladyshev, V. N., & Hatfield, D. L. (2007). Biosynthesis of selenocysteine on its tRNA in eukaryotes. PLoS biology, 5(1), e4.
  More info

  Selenocysteine (Sec) is cotranslationally inserted into protein in response to UGA codons and is the 21st amino acid in the genetic code. However, the means by which Sec is synthesized in eukaryotes is not known. Herein, comparative genomics and experimental analyses revealed that the mammalian Sec synthase (SecS) is the previously identified pyridoxal phosphate-containing protein known as the soluble liver antigen. SecS required selenophosphate and O-phosphoseryl-tRNA([Ser]Sec) as substrates to generate selenocysteyl-tRNA([Ser]Sec). Moreover, it was found that Sec was synthesized on the tRNA scaffold from selenide, ATP, and serine using tRNA([Ser]Sec), seryl-tRNA synthetase, O-phosphoseryl-tRNA([Ser]Sec) kinase, selenophosphate synthetase, and SecS. By identifying the pathway of Sec biosynthesis in mammals, this study not only functionally characterized SecS but also assigned the function of the O-phosphoseryl-tRNA([Ser]Sec) kinase. In addition, we found that selenophosphate synthetase 2 could synthesize monoselenophosphate in vitro but selenophosphate synthetase 1 could not. Conservation of the overall pathway of Sec biosynthesis suggests that this pathway is also active in other eukaryotes and archaea that synthesize selenoproteins.
• Xu, X., Carlson, B. A., Zhang, Y., Mix, H., Kryukov, G. V., Glass, R. S., Berry, M. J., Gladyshev, V. N., & Hatfield, D. L. (2007). New developments in selenium biochemistry: Selenocysteine biosynthesis in eukaryotes and archaea. Biological Trace Element Research, 119(3), 234-241.
  More info

  PMID: 17916946;Abstract: We used comparative genomics and experimental analyses to show that (1) eukaryotes and archaea, which possess the selenocysteine (Sec) protein insertion machinery contain an enzyme, O-phosphoseryl-transfer RNA (tRNA)[Ser]Sec kinase (designated PSTK), which phosphorylates seryl-tRNA[Ser]Sec to form O-phosphoseryl-tRNA[Ser]Sec and (2) the Sec synthase (SecS) in mammals is a pyridoxal phosphate-containing protein previously described as the soluble liver antigen (SLA). SecS uses the product of PSTK, O-phosphoseryl-tRNA[Ser]Sec, and selenophosphate as substrates to generate selenocysteyl-tRNA[Ser]Sec. Sec could be synthesized on tRNA[Ser]Sec from selenide, adenosine triphosphate (ATP), and serine using tRNA[Ser]Sec, seryl-tRNA synthetase, PSTK, selenophosphate synthetase, and SecS. The enzyme that synthesizes monoselenophosphate is a previously identified selenoprotein, selenophosphate synthetase 2 (SPS2), whereas the previously identified mammalian selenophosphate synthetase 1 did not serve this function. Monoselenophosphate also served directly in the reaction replacing ATP, selenide, and SPS2, demonstrating that this compound was the active selenium donor. Conservation of the overall pathway of Sec biosynthesis suggests that this pathway is also active in other eukaryotes and archaea that contain selenoproteins. © Humana Press Inc. 2007.
• Xu, X., Carlson, B. A., Zhang, Y., Mix, H., Kryukov, G. V., Glass, R. S., Berry, M. J., Gladyshev, V. N., & Hatfield, D. L. (2007). New developments in selenium biochemistry: selenocysteine biosynthesis in eukaryotes and archaea. Biological trace element research, 119(3), 234-41.
  More info

  We used comparative genomics and experimental analyses to show that (1) eukaryotes and archaea, which possess the selenocysteine (Sec) protein insertion machinery contain an enzyme, O-phosphoseryl-transfer RNA (tRNA) [Ser]Sec kinase (designated PSTK), which phosphorylates seryl-tRNA [Ser]Sec to form O-phosphoseryl-tRNA [Ser]Sec and (2) the Sec synthase (SecS) in mammals is a pyridoxal phosphate-containing protein previously described as the soluble liver antigen (SLA). SecS uses the product of PSTK, O-phosphoseryl-tRNA[Ser]Sec, and selenophosphate as substrates to generate selenocysteyl-tRNA [Ser]Sec. Sec could be synthesized on tRNA [Ser]Sec from selenide, adenosine triphosphate (ATP), and serine using tRNA[Ser]Sec, seryl-tRNA synthetase, PSTK, selenophosphate synthetase, and SecS. The enzyme that synthesizes monoselenophosphate is a previously identified selenoprotein, selenophosphate synthetase 2 (SPS2), whereas the previously identified mammalian selenophosphate synthetase 1 did not serve this function. Monoselenophosphate also served directly in the reaction replacing ATP, selenide, and SPS2, demonstrating that this compound was the active selenium donor. Conservation of the overall pathway of Sec biosynthesis suggests that this pathway is also active in other eukaryotes and archaea that contain selenoproteins.
• A., G., Glass, R. S., Lichtenberger, D. L., & Evans, D. H. (2006). Iron-only hydrogenase mimics. Thermodynamic aspects of the use of electrochemistry to evaluate catalytic efficiency for hydrogen generation. Inorganic Chemistry, 45(23), 9181-9184.
  More info

  PMID: 17083215;Abstract: Voltammetry is widely used for the evaluation of iron-only hydrogenase mimics and other potential catalysts for hydrogen generation using various dipolar aprotic solvents. Effective catalysts show enhanced current in the presence of a proton donor at the potential where the catalyst is reduced. To facilitate the comparison of catalytic efficiencies, this paper provides a simple means of calculating the standard potential for reduction of the acid, HA, according to the half reaction 2HA + 2e- ⇌ H2 + 2A-. This standard potential depends on the pKa of HA in the solvent being used. It is thermodynamically impossible for reduction of HA to occur at less negative potentials than the standard potential, and the most effective catalysts will operate at potentials as close as possible to the standard potential. In addition, direct reduction of HA at the electrode will compete with the catalyzed reduction, thus complicating evaluation of the rate of the catalyzed reaction. Glassy carbon electrodes, commonly used in such evaluations, show a quite large overpotential for direct reduction of HA so that the necessary corrections are small. However, catalysis at very negative potentials will be contaminated by significant direct reduction of HA at glassy carbon. It is demonstrated that direct reduction can be almost completely suppressed by using a mercury or amalgamated gold electrode, even at very negative potentials. © 2006 American Chemical Society.
• Block, E., Dikarev, E. V., Glass, R. S., Jin, J., Bo, L. i., Xiaojie, L. i., & Zhang, S. (2006). Synthesis, structure, and chemistry of new, mixed group 14 and 16 heterocycles: Nucleophile-induced ring contraction of mesocyclic dications. Journal of the American Chemical Society, 128(46), 14949-14961.
  More info

  PMID: 17105306;Abstract: More than 40 new 4- to 12-membered ring heterocycles containing various combinations of Group 14 and 16 elements Si, Sn, S, Se, and Te have been synthesized and fully characterized. Synthesis of these small-ring as well as medium-ring (mesocyclic) heterocycles from α,ω-dihalides is facilitated by the presence of gem-dialkylsilyl and gem-dialkylstannyl groups in the precursors. Conformations of several of the new ring systems in the solid state have been determined by X-ray crystal structure analysis. Oxidation of mixed S(Se, Te)/Si eight-membered ring mesocycles with NOPF6 or Br2 gives dications or a bicyclic dibromide, respectively, which can be characterized by NMR methods. On treatment with nucleophiles, mesocyclic dications, or the corresponding radical cations undergo ring contraction, giving five- or six-membered ring heterocycles. Photolysis of a S/Se four-membered ring heterocycle gives selenoformaldehyde, trapped in 80% yield with 2,3-dimethyl-1,3-butadiene. © 2006 American Chemical Society.
• Block, E., Dikarev, E. V., Glass, R. S., Jin, J., Li, B., Li, X., & Zhang, S. (2006). Synthesis, structure, and chemistry of new, mixed group 14 and 16 heterocycles: nucleophile-induced ring contraction of mesocyclic dications. Journal of the American Chemical Society, 128(46), 14949-61.
  More info

  More than 40 new 4- to 12-membered ring heterocycles containing various combinations of Group 14 and 16 elements Si, Sn, S, Se, and Te have been synthesized and fully characterized. Synthesis of these small-ring as well as medium-ring (mesocyclic) heterocycles from alpha,omega-dihalides is facilitated by the presence of gem-dialkylsilyl and gem-dialkylstannyl groups in the precursors. Conformations of several of the new ring systems in the solid state have been determined by X-ray crystal structure analysis. Oxidation of mixed S(Se, Te)/Si eight-membered ring mesocycles with NOPF6 or Br2 gives dications or a bicyclic dibromide, respectively, which can be characterized by NMR methods. On treatment with nucleophiles, mesocyclic dications, or the corresponding radical cations undergo ring contraction, giving five- or six-membered ring heterocycles. Photolysis of a S/Se four-membered ring heterocycle gives selenoformaldehyde, trapped in 80% yield with 2,3-dimethyl-1,3-butadiene.
• Felton, G. A., Glass, R. S., Lichtenberger, D. L., & Evans, D. H. (2006). Iron-only hydrogenase mimics. Thermodynamic aspects of the use of electrochemistry to evaluate catalytic efficiency for hydrogen generation. Inorganic chemistry, 45(23), 9181-4.
  More info

  Voltammetry is widely used for the evaluation of iron-only hydrogenase mimics and other potential catalysts for hydrogen generation using various dipolar aprotic solvents. Effective catalysts show enhanced current in the presence of a proton donor at the potential where the catalyst is reduced. To facilitate the comparison of catalytic efficiencies, this paper provides a simple means of calculating the standard potential for reduction of the acid, HA, according to the half reaction 2HA + 2e- H2 + 2A-. This standard potential depends on the pKa of HA in the solvent being used. It is thermodynamically impossible for reduction of HA to occur at less negative potentials than the standard potential, and the most effective catalysts will operate at potentials as close as possible to the standard potential. In addition, direct reduction of HA at the electrode will compete with the catalyzed reduction, thus complicating evaluation of the rate of the catalyzed reaction. Glassy carbon electrodes, commonly used in such evaluations, show a quite large overpotential for direct reduction of HA so that the necessary corrections are small. However, catalysis at very negative potentials will be contaminated by significant direct reduction of HA at glassy carbon. It is demonstrated that direct reduction can be almost completely suppressed by using a mercury or amalgamated gold electrode, even at very negative potentials.
• Glass, R. S., Block, E., Lorance, E., Zakai, U. I., Gruhn, N. E., Jin, J., & Zhang, S. (2006). The Si-Si effect on ionization of beta-disilanyl sulfides and selenides. Journal of the American Chemical Society, 128(39), 12685-92.
  More info

  The ionization energies of conformationally constrained, newly synthesized beta-disilanyl sulfides and selenides were determined by photoelectron spectroscopy. These ionization energies reflect substantial (0.53-0.75 eV) orbital destabilizations. The basis for these destabilizations was investigated by theoretical calculations, which reveal geometry-dependent interaction between sulfur or selenium lone pair orbitals and sigma-orbitals, especially Si-Si sigma-orbitals. These results presage facile redox chemistry for these compounds and significantly extend the concept of sigma-stabilization of electron-deficient centers.
• Glass, R. S., Block, E., Lorance, E., Zakai, U. I., Gruhn, N. E., Jin, J., & Zhang, S. (2006). The Si-Si effect on ionization of β-disilanyl sulfides and selenides. Journal of the American Chemical Society, 128(39), 12685-12692.
  More info

  PMID: 17002362;Abstract: The ionization energies of conformationally constrained, newly synthesized β-disilanyl sulfides and selenides were determined by photoelectron spectroscopy. These ionization energies reflect substantial (0.53-0.75 eV) orbital destabilizations. The basis for these destabilizations was investigated by theoretical calculations, which reveal geometry-dependent interaction between sulfur or selenium lone pair orbitals and σ-orbitals, especially Si-Si σ-orbitals. These results presage facile redox chemistry for these compounds and significantly extend the concept of σ-stabilization of electron-deficient centers. © 2006 American Chemical Society.
• Manley, S. A., George, G. N., Pickering, I. J., Glass, R. S., Prenner, E. J., Yamdagni, R., Qiao, W. u., & Gailer, J. (2006). The seleno bis(S-glutathionyl) arsinium ion is assembled in erythrocyte lysate. Chemical Research in Toxicology, 19(4), 601-607.
  More info

  PMID: 16608173;Abstract: Approximately 75 million people are currently exposed to arsenic concentrations in drinking water, which is associated with the development of internal cancers. One way to ameliorate this undesirable situation is to remove arsenic (arsenite and arsenate) from drinking water. An alternative approach is the development of an inexpensive palliative dietary supplement that promotes the excretion of intestinally absorbed arsenite from the body. To this end, the simultaneous administration of New Zealand white rabbits with arsenite and selenite resulted in the biliary excretion of the seleno-bis (S-glutathionyl) arsinium ion, [(GS)2AsSe]-. This apparent detoxification mechanism has been recently extended to environmentally relevant doses [Gailer, J., Ruprecht, L., Reitmeir, P., Benker, B., and Schramel, P. (2004) Appl. Organometal. Chem. 18, 670-675]. The site of formation of this excretory product in the organism, however, is unknown. To investigate if [(GS) 2AsSe]- is formed in rabbit blood, we added arsenite and selenite and analyzed blood aliquots using arsenic and selenium X-ray absorption spectroscopy. The characteristic arsenic and selenium X-ray absorption spectra of [(GS)2AsSe]- were detected within 2 min after addition and comprised 95% of the blood selenium 30 min after addition. To elucidate if erythrocytes are involved in the biosynthesis of [(GS)2AsSe] - in blood, arsenite and 77Se-selenite were added to rabbit erythrocyte lysate and the obtained solution was analyzed by 77Se NMR spectroscopy (273 K). This resulted in a 77Se NMR signal with a chemical shift identical to that of synthetic [(GS) 2AsSe]- added to lysate. Combined, these results demonstrate that [(GS)2AsSe]- is rapidly formed in blood and that erythrocytes are an important site for the in vivo formation of this toxicologically important metabolite. © 2006 American Chemical Society.
• Manley, S. A., George, G. N., Pickering, I. J., Glass, R. S., Prenner, E. J., Yamdagni, R., Wu, Q., & Gailer, J. (2006). The seleno bis(S-glutathionyl) arsinium ion is assembled in erythrocyte lysate. Chemical research in toxicology, 19(4), 601-7.
  More info

  Approximately 75 million people are currently exposed to arsenic concentrations in drinking water, which is associated with the development of internal cancers. One way to ameliorate this undesirable situation is to remove arsenic (arsenite and arsenate) from drinking water. An alternative approach is the development of an inexpensive palliative dietary supplement that promotes the excretion of intestinally absorbed arsenite from the body. To this end, the simultaneous administration of New Zealand white rabbits with arsenite and selenite resulted in the biliary excretion of the seleno-bis (S-glutathionyl) arsinium ion, [(GS)2AsSe]-. This apparent detoxification mechanism has been recently extended to environmentally relevant doses [Gailer, J., Ruprecht, L., Reitmeir, P., Benker, B., and Schramel, P. (2004) Appl. Organometal. Chem. 18, 670-675]. The site of formation of this excretory product in the organism, however, is unknown. To investigate if [(GS)2AsSe]- is formed in rabbit blood, we added arsenite and selenite and analyzed blood aliquots using arsenic and selenium X-ray absorption spectroscopy. The characteristic arsenic and selenium X-ray absorption spectra of [(GS)2AsSe]- were detected within 2 min after addition and comprised 95% of the blood selenium 30 min after addition. To elucidate if erythrocytes are involved in the biosynthesis of [(GS)2AsSe]- in blood, arsenite and 77Se-selenite were added to rabbit erythrocyte lysate and the obtained solution was analyzed by 77Se NMR spectroscopy (273 K). This resulted in a 77Se NMR signal with a chemical shift identical to that of synthetic [(GS)2AsSe]- added to lysate. Combined, these results demonstrate that [(GS)2AsSe]- is rapidly formed in blood and that erythrocytes are an important site for the in vivo formation of this toxicologically important metabolite.
• Xu, X., Carlson, B. A., Mix, H., Zhang, Y., Saira, K., Glass, R. S., Berry, M. J., Gladyshev, V. N., & Hatfield, D. L. (2006). Biosynthesis of selenocysteine on its tRNA in eukaryotes.. PLoS biology, 5(1), e4.
  More info

  PMID: 17194211;PMCID: PMC1717018;Abstract: Selenocysteine (Sec) is cotranslationally inserted into protein in response to UGA codons and is the 21st amino acid in the genetic code. However, the means by which Sec is synthesized in eukaryotes is not known. Herein, comparative genomics and experimental analyses revealed that the mammalian Sec synthase (SecS) is the previously identified pyridoxal phosphate-containing protein known as the soluble liver antigen. SecS required selenophosphate and O-phosphoseryl-tRNA([Ser]Sec) as substrates to generate selenocysteyl-tRNA([Ser]Sec). Moreover, it was found that Sec was synthesized on the tRNA scaffold from selenide, ATP, and serine using tRNA([Ser]Sec), seryl-tRNA synthetase, O-phosphoseryl-tRNA([Ser]Sec) kinase, selenophosphate synthetase, and SecS. By identifying the pathway of Sec biosynthesis in mammals, this study not only functionally characterized SecS but also assigned the function of the O-phosphoseryl-tRNA([Ser]Sec) kinase. In addition, we found that selenophosphate synthetase 2 could synthesize monoselenophosphate in vitro but selenophosphate synthetase 1 could not. Conservation of the overall pathway of Sec biosynthesis suggests that this pathway is also active in other eukaryotes and archaea that synthesize selenoproteins.
• Glass, R. S., & Singh, M. S. (2005). Reaction of (μ-S)₂Fe₂(CO)₆ dianion with 1,2-vinyl and aryl diiodides. Arkivoc, 2005(6), 185-190.
  More info

  Abstract: The inorganic dithiolate, (μ-S)2Fe2(CO) 62-, reductively deiodinates trans-1,2-diiodo-1,2- diphenylethene to afford diphenylacetylene in 79% yield. Reaction of (μ-S)2Fe2(CO)62- with 1,2-diiodobenzene and 2,3-diiodotoluene results in the formation of the benzenedithiolate complex (μ-S)2Fe2(CO)6 and toluenedithiolate complex (μ-S2C6H4Me) Fe2(CO)6 in 42% and 48% isolated yields, respectively. These reactions appear to involve reductive deiodination of 1,2-diiodobenzene and 2,3-diiodotoluene with (μ-S)2Fe2(CO)62- to the corresponding benzynes followed by trapping with the concomitantly formed disulfide (μ-S2)Fe2(CO) 6, to give the observed complexes. As such, these reactions involve the first examples of thermal [2+2] cycloaddition of benzyne to the S-S bond of an inorganic disulfide. Although the reaction was not observed on treatment of other substituted 1,2-diiodobenzenes, 1,2,4,5-tetraiodobenzene was monodeiodinated to 1,2,4-triiodobenzene in 62% isolated yield. ©ARKAT.
• Glass, R. S., Gruhn, N. E., Lorance, E., Singh, M. S., Stessman, N. Y., & Zakai, U. I. (2005). Synthesis, gas-phase photoelectron spectroscopic, and theoretical studies of stannylated dinuclear iron dithiolates. Inorganic chemistry, 44(16), 5728-37.
  More info

  Stannylated dinuclear iron dithiolates (mu-SSnMe(2)CH(2)S)[Fe(CO)(3)](2), (mu-SCH(2)SnMe(2)CH(2)S) [Fe(CO)(3)](2), and (mu-SCH(2)SnMe(3))(2)[Fe(CO)(3)](2), which are structurally similar to the active site of iron-only hydrogenase, were synthesized and studied by gas-phase photoelectron spectroscopy. The orbital origins of ionizations were assigned by comparison of He I and He II photoelectron spectra and with the aid of hybrid density functional electronic structure calculations. Stannylation lowers the ionization energy of sulfur lone pair orbitals in these systems owing to a geometry-dependent interaction. The Fe-Fe sigma bond, which is the HOMO in all these systems, is also substantially destabilized by stannylation due to a previously unrecognized geometry-dependent interaction between axial sulfur lone pair orbitals and the Fe-Fe sigma bond. Since cleaving the Fe-Fe sigma bond is a key step in the mechanism of action of iron-only hydrogenase, these newly recognized geometry-dependent interactions may be utilized in designing biologically inspired hydrogenase catalysts.
• Glass, R. S., Gruhn, N. E., Lorance, E., Singh, M. S., Y., N., & Zakai, U. I. (2005). Synthesis, gas-phase photoelectron spectroscopic and theoretical studies of stannylated dinuclear iron dithiolates. ACS National Meeting Book of Abstracts, 229(1), INOR-571.
  More info

  Abstract: Hydrogenases catalyze the production and uptake of dihydrogen and are of interest as catalysts in the use of H 2 as a fuel both in its production and consumption in fuel cells. Chemical models for the active site [Fe]-hydrogenase are studied to provide insight into the catalytic mechanism for the enzyme. An accepted mechanism of hydrogen production involves protonation of the iron-iron bond, which is most effective in models containing electron-donating cyanide and phosphine ligands. The greater electon density imparted upon sulfur by a neighboring stannyl group is proposed to have a similar effect without the need for these ligands. This is an abstract of a paper presented at the 229th ACS National Meeting (San Diego, CA 3/13-17/2005).
• Glass, R. S., Gruhn, N. E., Lorance, E., Singh, M. S., Y., N., & Zakai, U. I. (2005). Synthesis, gas-phase photoelectron spectroscopic, and theoretical studies of stannylated dinuclear iron dithiolates. Inorganic Chemistry, 44(16), 5728-5737.
  More info

  PMID: 16060624;Abstract: Stannylated dinuclear iron dithiolates (μ-SSnMe2CH 2S)[Fe(CO)3]2, (μ-SCH2SnMe 2CH2S) [Fe(CO)3]2, and (μ-SCH2-SnMe3)2[Fe(CO)3] 2, which are structurally similar to the active site of iron-only hydrogenase, were synthesized and studied by gas-phase photoelectron spectroscopy. The orbital origins of ionizations were assigned by comparison of He I and He II photoelectron spectra and with the aid of hybrid density functional electronic structure calculations. Stannylation lowers the ionization energy of sulfur lone pair orbitals in these systems owing to a geometry-dependent interaction. The Fe-Fe σ bond, which is the HOMO in all these systems, is also substantially destabilized by stannylation due to a previously unrecognized geometry-dependent interaction between axial sulfur lone pair orbitals and the Fe-Fe σ bond. Since cleaving the Fe-Fe σ bond is a key step in the mechanism of action of iron-only hydrogenase, these newly recognized geometry-dependent interactions may be utilized in designing biologically inspired hydrogenase catalysts. © 2005 American Chemical Society.
• Glass, R. S., Paschos, A., Reissmann, S., Singh, M. S., Wang, H., & Böck, A. (2005). Generation of the [NiFe] hydrogenase active site (sulfur's the one!). Phosphorus, Sulfur and Silicon and the Related Elements, 180(5-6), 1183-1195.
  More info

  Abstract: Chemical and biochemical methods were used to unravel the unprecedented pathway by which the CN ligands of iron in [NiFe] hydrogenase are introduced. Carbamoyl phosphate is the one carbon precursor of these ligands, and reactions involving a protein cysteinyl sulfur are key for processing this precursor into CN ligands. Copyright © Taylor & Francis Inc.
• Block, E., Glass, R. S., Jacobsen, N. E., Johnson, S., Kahakachchi, C., Kamiński, R., Skowrońska, A., Boakye, H. T., Tyson, J. F., & Uden, P. C. (2004). Identification and synthesis of a novel selenium-sulfur amino acid found in selenized yeast: Rapid indirect detection NMR methods for characterizing low-level organoselenium compounds in complex matrices. Journal of Agricultural and Food Chemistry, 52(12), 3761-3771.
  More info

  PMID: 15186094;Abstract: After proteolytic digestion, aqueous extraction, and derivatization with diethyl pyrocarbonate or ethyl chloroformate, HPLC-inductively coupled plasma (ICP)-MS, GC-atomic emission detection (AED), and GC-MS analysis of high-selenium yeast stored at room temperature for more than 10 years showed selenomethionine as the major Se product along with substantial amounts of selenomethionine selenoxide hydrate and the previously unreported selenoamino acid having a Se-S bond, S-(methylseleno)cysteine. The identity of the latter compound was confirmed by synthesis. The natural product was shown to be different from a synthetic sample of the isomeric compound Se-(methylthio)- selenocysteine. Selenium-specific NMR spectroscopic methods were developed to directly analyze the aqueous extracts of the hydrolyzed selenized yeast without derivatization or separation. Selenomethionine and S-(methylseleno)cysteine were identified by 77Se-1H HMQC-TOCSY experiments.
• Block, E., Glass, R. S., Jacobsen, N. E., Johnson, S., Kahakachchi, C., Kamiński, R., Skowrońska, A., Boakye, H. T., Tyson, J. F., & Uden, P. C. (2004). Identification and synthesis of a novel selenium-sulfur amino acid found in selenized yeast: Rapid indirect detection NMR methods for characterizing low-level organoselenium compounds in complex matrices. Journal of agricultural and food chemistry, 52(12), 3761-71.
  More info

  After proteolytic digestion, aqueous extraction, and derivatization with diethyl pyrocarbonate or ethyl chloroformate, HPLC-inductively coupled plasma (ICP)-MS, GC-atomic emission detection (AED), and GC-MS analysis of high-selenium yeast stored at room temperature for more than 10 years showed selenomethionine as the major Se product along with substantial amounts of selenomethionine selenoxide hydrate and the previously unreported selenoamino acid having a Se-S bond, S-(methylseleno)cysteine. The identity of the latter compound was confirmed by synthesis. The natural product was shown to be different from a synthetic sample of the isomeric compound Se-(methylthio)selenocysteine. Selenium-specific NMR spectroscopic methods were developed to directly analyze the aqueous extracts of the hydrolyzed selenized yeast without derivatization or separation. Selenomethionine and S-(methylseleno)cysteine were identified by 77Se-1H HMQC-TOCSY experiments.
• Dufield, D. R., Wilson, G. S., Glass, R. S., & Schöneich, C. (2004). Selective Site-Specific Fenton Oxidation of Methionine in Model Peptides: Evidence for a Metal-Bound Oxidant. Journal of Pharmaceutical Sciences, 93(5), 1122-1130.
  More info

  PMID: 15067689;Abstract: The metal-catalyzed oxidation (MCO) of proteins represents an important pathway for protein degradation. Although many mechanistic details of MCO are currently unknown, such mechanistic information would greatly benefit formulation scientists in the rational design and analysis of protein formulations. Here, we describe the Fenton oxidation (by Fe2+/H 2O2) of several Met-, Tyr-, and His containing model peptides, including one derivative containing a conformationally restricted norbornyl Met analogue (Nor), Nor-Gly-His-Met-NH2. Our results will provide evidence for a metal-bound reactive oxygen species selectively oxidizing Met to Met sulfoxide, indicating a Met-specific oxidant and arguing against the involvement of freely diffusible hydroxyl radicals. The Fenton oxidation of Nor-Gly-His-Met-NH2 yields a 2:1 preference for sulfoxide formation at the C-terminal Met versus the N-terminal Nor residue, respectively, while incubation of the peptide with H2O2 alone results in a 1:1 ratio. These results are rationalized by the better access of the thioether side chain of the flexible C-terminal Met residue to the peptide-bound iron compared with the conformationally restricted Nor residue. It is commonly believed that Fenton oxidation reactions involve hydroxyl radicals, and that Met oxidation in proteins is predominantly controlled by the surface-accessibility of the respective Met residues. However, occasionally protein oxidation in formulations shows selectivities, which are not consistent with these paradigms. Our results demonstrate additional features of the Fenton reaction such as the formation of a metal-bound oxidant specific for Met (and not Tyr or His), which may assist formulation scientists in the rationalization of unexpected oxidation selectivities. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association.
• Dufield, D. R., Wilson, G. S., Glass, R. S., & Schöneich, C. (2004). Selective site-specific fenton oxidation of methionine in model peptides: evidence for a metal-bound oxidant. Journal of pharmaceutical sciences, 93(5), 1122-30.
  More info

  The metal-catalyzed oxidation (MCO) of proteins represents an important pathway for protein degradation. Although many mechanistic details of MCO are currently unknown, such mechanistic information would greatly benefit formulation scientists in the rational design and analysis of protein formulations. Here, we describe the Fenton oxidation (by Fe(2+)/H(2)O(2)) of several Met-, Tyr-, and His containing model peptides, including one derivative containing a conformationally restricted norbornyl Met analogue (Nor), Nor-Gly-His-Met-NH(2). Our results will provide evidence for a metal-bound reactive oxygen species selectively oxidizing Met to Met sulfoxide, indicating a Met-specific oxidant and arguing against the involvement of freely diffusible hydroxyl radicals. The Fenton oxidation of Nor-Gly-His-Met-NH(2) yields a 2:1 preference for sulfoxide formation at the C-terminal Met versus the N-terminal Nor residue, respectively, while incubation of the peptide with H(2)O(2) alone results in a 1:1 ratio. These results are rationalized by the better access of the thioether side chain of the flexible C-terminal Met residue to the peptide-bound iron compared with the conformationally restricted Nor residue. It is commonly believed that Fenton oxidation reactions involve hydroxyl radicals, and that Met oxidation in proteins is predominantly controlled by the surface-accessibility of the respective Met residues. However, occasionally protein oxidation in formulations shows selectivities, which are not consistent with these paradigms. Our results demonstrate additional features of the Fenton reaction such as the formation of a metal-bound oxidant specific for Met (and not Tyr or His), which may assist formulation scientists in the rationalization of unexpected oxidation selectivities.
• Block, E., Shan, Z., Glass, R. S., & Fabian, J. (2003). Revised structure of a purported 1,2-dioxin: A combined experimental and theoretical study. Journal of Organic Chemistry, 68(10), 4108-4111.
  More info

  PMID: 12737603;Abstract: 3,6-Bis(p-tolyl)-1,2-dioxin (1g) was suggested by Shine and Zhao as a product in an electron-transfer (ET) photochemical reaction. This photoproduct is instead shown to be (E)-1,4-di-p-tolylbut-2-ene-1,4-dione ((E)-4a). Ab initio and DFT calculations indicate that ring-closed 1,2-dioxin is thermodynamically far less stable than open-chain but-2-ene-1,3-dione. These calculations indicate that (E)-4a is formed via the cation radical of 1g, which sequentially isomerizes to a novel (σ-radical with an O,O 3e bond [(Z)-4a]+•, undergoes ET to give (Z)-4a, and then photoisomerizes to (E)-4a.
• Glass, R. S., Deardorff, D. R., Y., N., & Carducci, M. D. (2003). (1a,6a,7a,7aβ)-2,3,5,6,7,7a-Hexahydro-1,6-epoxy-1H-pyrrolizin-7-ol. Acta Crystallographica Section E: Structure Reports Online, 59(9), o1270-o1271.
  More info

  Abstract: The C7H11NO2 compound, an intermediate in a synthetic approach to the pyrrolizidine alkaloid loline was discussed. The compound has a brendane skeleton with a 91.8(2)° bond angle for the bridging carbon bearing the OH group. The x-ray show that the molecule was an analog of brendane. The results show that the molecules of compound form infinite linear chains through hydrogen bonding of the alcohol moiety of one molecule with the amine moiety of the next molecule.
• Lorance, E. D., Glass, R. S., Block, E., & Li, X. (2003). Synthesis, electrochemistry, and gas-phase photoelectron spectroscopic and theoretical studies of 3,6-bis(perfluoroalkyl)-1,2-dithiins. The Journal of organic chemistry, 68(21), 8110-4.
  More info

  3,6-bis(trifluoromethyl)- and 3,6-bis(pentafluoroethyl)-1,2-dithiin (1a,b), the first known perfluoroalkyl-substituted 1,2-dithiins, were synthesized from (Z,Z)-1,4-bis(tert-butylthio)-1,3-butadiene (2) to evaluate the effects of electron-withdrawing groups on the ionization and oxidation potentials of 1,2-dithiins. Analysis of the photoelectron spectra of 1a and 1b provided a basis for assigning orbital compositions. Ab initio calculations on these compounds showed that they adopt a twist geometry as does 1,2-dithiin (1c) itself. Cyclic voltammetric studies on 1a and 1b revealed a reversible oxidation followed by an irreversible oxidation at much more positive potentials than for 1,2-dithiin and 3,6-dimethyl-1,2-dithiin (1d). The oxidation potentials determined electrochemically do not correlate with the ionization potentials determined by photoelectron spectroscopy. This result supports the previously advanced hypothesis that there is a geometry change on electrochemical oxidation leading to a planar radical cation.
• Lorance, E. D., Glass, R. S., Block, E., & Xiaojie, L. i. (2003). Synthesis, electrochemistry, and gas-phase photoelectron spectroscopic and theoretical studies of 3,6-bis(perfluoroalkyl)-1,2-dithiins. Journal of Organic Chemistry, 68(21), 8110-8114.
  More info

  PMID: 14535791;Abstract: 3,6-Bis(trifluoromethyl)- and 3,6-bis(pentafluoroethyl)-1,2-dithiin (la,b), the first known perfluoroalkyl-substituted 1,2-dithiins, were synthesized from (Z,Z)-1,4-bis(tert-butylthio)-1,3-butadiene (2) to evaluate the effects of electron-withdrawing groups on the ionization and oxidation potentials of 1,2-dithiins. Analysis of the photoelectron spectra of la and lb provided a basis for assigning orbital compositions. Ab initio calculations on these compounds showed that they adopt a twist geometry as does 1,2-dithiin (1c) itself. Cyclic voltammetric studies on la and lb revealed a reversible oxidation followed by an irreversible oxidation at much more positive potentials than for 1,2-dithiin and 3,6-dimethyl-1,2-dithiin (1d). The oxidation potentials determined electrochemically do not correlate with the ionization potentials determined by photoelectron spectroscopy. This result supports the previously advanced hypothesis that there is a geometry change on electrochemical oxidation leading to a planar radical cation.
• Potapov, V. A., Amosova, S. V., Doron'kina, I. V., & Glass, R. S. (2003). Unexpected reaction of (Z)-1,2-bis(benzylseleno)-ethene: The formation of 1,4-diselenin. Sulfur Letters, 26(4), 137-140.
  More info

  Abstract: Heating (Z)-1,2-bis(benzylseleno)ethene at 140-180 °C leads to 1,4-diselenin (79% yield) and dibenzyl selenide. This unusual reaction represents a convenient method for preparing 1,4-diselenin.
• Reissmann, S., Hochleitner, E., Wang, H., Paschos, A., Lottspeich, F., Glass, R. S., & Böck, A. (2003). Taming of a poison: Biosynthesis of the NiFE-hydrogenase cyanide ligands. Science, 299(5609), 1067-1070.
  More info

  PMID: 12586941;Abstract: NiFe-hydrogenases have an Ni-Fe site in which the iron has one CO and two CN groups as ligands. Synthesis of the CN ligands requires the activity of two hydrogenase maturation proteins: HypF and HypE. HypF is a carbamoyl-transferase that transfers the carbamoyl moiety of carbamoyladenylate to the COOH-terminal cysteine of HypE and thus forms an enzyme-thiocarbamate. HypE dehydrates the S-carbamoyl moiety in an adenosine triphosphate-dependent process to yield the enzyme thiocyanate. Chemical model reactions corroborate the feasibility of this unprecedented biosynthetic route and show that thiocyanates can donate CN to iron. This finding underscores a striking parallel between biochemistry and organometallic chemistry in the formation of an iron-cyano complex.
• Gailer, J., George, G. N., Harris, H. H., Pickering, I. J., Prince, R. C., Somogyi, A., Buttigieg, G. A., Glass, R. S., & Denton, M. B. (2002). Synthesis, purification, and structural characterization of the dimethyldiselenoarsinate anion. Inorganic Chemistry, 41(21), 5426-5432.
  More info

  PMID: 12377037;Abstract: A novel arsenic-selenium solution species was synthesized by reacting equimolar sodium selenite and sodium dimethylarsinate with 10 mol equiv of glutathione (pH 7.5) in aqueous solution. The solution species showed a single 77Se NMR resonance at 112.8 ppm. Size-exclusion chromatography (SEC) using an inductively coupled plasma atomic emission spectrometer (ICP-AES) as the simultaneous arsenic-, selenium-, sulfur-, and carbon-specific detector revealed an arsenic-selenium moiety with an As:Se molar ratio of 1:2. Electrospray ionization mass spectrometry (ESI-MS) of the chromatographically purified compound showed a molecular mass peak at m/z 263 in the negative ion mode. Fragmentation of the parent ion (ESI-MS-MS) produced (CH3)2As- and Se2-fragments. Arsenic and selenium extended X-ray absorption fine structure spectroscopy (EXAFS) of the purified species revealed two As-C interactions at 1.943 Å and two As-Se interactions at 2.279 Å. On the basis of these results this novel solution species is identified as the dimethyldiselenoarsinate anion.
• Gailer, J., George, G. N., Pickering, I. J., Buttigieg, G. A., Denton, M., & Glass, R. S. (2002). Synthesis, X-ray absorption spectroscopy and purification of the seleno-bis (S-glutathionyl) arsinium anion from selenide, arsenite and glutathione. Journal of Organometallic Chemistry, 650(1-2), 108-113.
  More info

  Abstract: We report a new synthesis of the seleno-bis (S-glutathionyl) arsinium anion, [(GS)2AsSe]-. An aqueous solution of bis-glutathionylarsenous acid. (GS)2As-OH, prepared form stoichiometric glutathione and arsenite, was reacted in situ with a solution of sodium hydrogen selenide, prepared from elemental selenium and sodium borohydride. Analysis of the arsenic and selenium K-edge X-ray absorption spectra indicated virtually quantitative formation of [(GS)2AsSe]- with As Se and As-S distances of 2.31 and 2.25 Å, respectively, and the concentrated sample allowed a definitive X-ray spectroscopic characterization. Size-exclusion chromatography was used to separate [(GS)2AsSe]- from residual borate in the reaction mixture. © 2002 Elsevier Sciences B.V. All rights reserved.
• Glass, R. S., Jouikov, V. V., & Bojkova, N. V. (2001). Electrochemical activation of dimethyl disulfide for electrophilic aromatic substitution. Journal of Organic Chemistry, 66(12), 4440-4443.
  More info

  PMID: 11397193;
• Kamiñski, R., Glass, R. S., & Skowroñska, A. (2001). A convenient synthesis of selenocarboxamides from nitriles. Synthesis, 1308-1310.
  More info

  Abstract: Aromatic and aliphatic nitriles can be conveniently converted into the corresponding selenocarboxamides with monoselenophosphate in aqueous alcohol in 50-94% yield.
• Paschos, A., Glass, R. S., & Böck, A. (2001). Carbamoylphosphate requirement for synthesis of the active center of [NiFe]-hydrogenases. FEBS Letters, 488(1-2), 9-12.
  More info

  PMID: 11163786;Abstract: The iron of the binuclear active center of [NiFe]-hydrogenases carries two CN and one CO ligands which are thought to confer to the metal a low oxidation and/or spin state essential for activity. Based on the observation that one of the seven auxiliary proteins required for the synthesis and insertion of the [NiFe] cluster contains a sequence motif characteristic of O-carbamoyl-transferases it was discovered that carbamoyl phosphate is essential for formation of active [NiFe]-hydrogenases in vivo and is specifically required for metal center synthesis suggesting that it is the source of the CO and CN ligands. A chemical path for conversion of a carbamoyl group into cyano and carbonyl moieties is postulated. © 2001 Federation of European Biochemical Societies.
• Block, E., Birringer, M., Deorazio, R., Fabian, J., Glass, R. S., Guo, C., Chunhong, H. e., Lorance, E., Qian, Q., Schroeder, T. B., Shan, Z., Thiruvazhi, M., Wilson, G. S., & Zhang, X. (2000). Synthesis, properties, oxidation, and electrochemistry of 1,2- dichalcogenins. Journal of the American Chemical Society, 122(21), 5052-5064.
  More info

  Abstract: Syntheses are presented of the 1,2-dichalcogenins: 1,2-dithiin, 1,2- diselenin, and 2-selenathiin, both substituted and unsubstituted. 1,2-Dithiin and 1,2-diselenin are prepared by reaction of PhCH2XNa (X = S or Se) with 1,4-bis(trimethylsilyl)-1,3-butadiyne followed by reductive cleavage and oxidation. 2-Selenathiin is similarly prepared using a mixture of PhCH2SeNa and PhCH2SNa. Reaction of titanacyclopentadienes with (SCN)2 or (SeCN)2 followed by bis(thiocyanate) or bis(selenocyanate) cyclization affords substituted 1,2-dithiins or 1,2-diselenins, respectively. With S2Cl2, 1,2- dithiins are directly formed from titanacyclopentadienes. Oxidation of 1,2- dithiins and 1,2-diselenins gives the corresponding 1-oxide and, with 1,2- dithiins and excess oxidant, 1,1-dioxides; oxidation of 2-selenathiin gives the 2-oxide. Electrochemical oxidation of 1,2-dichalcogenins, which have a twisted geometry, affords planar radical cations by an EC mechanism. One- electron AlCl3 oxidation of 3,6-diphenyl-1,2-dithiin gives the corresponding radical cation, characterized by EPR spectroscopy. Theoretical calculations result in a flattened structure for the 1,2-dithiin radical cation and a fully planar structure for the 1,2-diselenin radical cation. The 77Se NMR chemical shifts of 1,2-diselenin are characteristically high-field-shifted with respect to open chain diselenides in good agreement with results of GIAO-DFT calculations based on MP2 and DFT optimum geometries.
• Gailer, J., George, G. N., Pickering, I. J., Prince, R. C., Ringwald, S. C., Pemberton, J. E., Glass, R. S., Younis, H. S., DeYoung, D. W., & Aposhian, H. V. (2000). A Metabolic Link Between Arsenite and Selenite: The Seleno-bis(S-glutathionyl) Arsinium Ion. Journal of the American Chemical Society, 122, 4637-4639.
• Gailer, J., George, G. N., Pickering, I. J., Prince, R. C., Ringwald, S. C., Pemberton, J. E., Glass, R. S., Younis, H. S., DeYoung, D. W., & Aposhian, H. V. (2000). A metabolic link between arsenite and selenite: The seleno-bis(S- glutathionyl) arsinium ion. Journal of the American Chemical Society, 122(19), 4637-4639.
  More info

  Abstract: Among the most startling observations in mammalian toxicology is that a lethal dose of selenium can be overcome by an otherwise lethal dose of arsenic. We report the molecular basis of this antagonism. Using X-ray absorption spectroscopy we have identified a new arsenic-selenium compound in the bile of rabbits injected with aqueous selenite and arsenite solutions. This compound contains equimolar arsenic and selenium and exhibits X-ray absorption spectra which are essentially identical with those of a synthetic species in solution which we have identified spectroscopically as the seleno- bis(S-glutathionyl) arsinium ion. The in vivo detection of this compound links the mammalian metabolism of arsenite, selenite, and sulfur. It provides a molecular basis for the antagonistic interaction between these metalloid compounds, and a potential explanation of the association of cancer with prolonged intake of inorganic arsenic in humans.
• Glass, R. S., & Stessman, N. Y. (2000). Synthesis of a redox active analogue of adenine. Tetrahedron Letters, 41(49), 9581-9584.
  More info

  Abstract: An analogue of adenine 3, in which the aminopyrimidine moiety is annulated to a cyclopentadienyl ring of ferrocene, was synthesized from ferrocenecarboxaldehyde. The key intermediate in this synthesis was 2-aminoferrocenenitrile, which was prepared regio- and stereoselectively. An X-ray crystallographic structure study of 6, a derivative of 3 obtained by acetylation, confirmed the structure of the product. (C) 2000 Elsevier Science Ltd.
• Glass, R. S., Gruhn, N. E., Lichtenberger, D. L., Lorance, E., Pollard, J. R., Birringer, M., Block, E., Deorazio, R., Chunhong, H. e., Shan, Z., & Zhang, X. (2000). Gas-phase photoelectron spectroscopic and theoretical studies of 1,2- dichalcogenins: Ionization energies, orbital assignments, and an explanation of their color. Journal of the American Chemical Society, 122(21), 5065-5074.
  More info

  Abstract: Gas-phase photoelectron spectroscopy and theoretical calculations are used to study the electronic structure of 1,2-dichalcogenins. Photoelectron spectra are reported for 1,2-dithiin, 3,6-dimethyl-1,2-dithiin, 3,6- diisopropyl-1,2-dithiin, 3,6-di-tert-butyl-1,2-dithiin, 2-selenathiin, 1,2- diselenin, 3,6-dimethyl-1,2-diselenin, and 3,6-di-tert-butyl-1,2-diselenin and are assigned on the basis of (a) trends in ionization cross sections as the ionization photon energy is varied and (b) shifts of the ionizations as chemical substitutions are made. The calculated properties of 1,2-dithiin and 3,6-dimethyl-1,2-dithiin are compared to experimental results. The first four filled frontier valence orbitals are associated with orbitals that can be described as being primarily carbon π and chalcogen lone pair in character. Comparison of spectra collected with He I, He II, and Ne I ionization sources for each compound indicate that there is a large degree of mixing of chalcogen and carbon character through most of the valence orbitals. The highest occupied molecular orbital of the selenium-containing compounds has more chalcogen character than the highest occupied molecular orbital of the 1,2-dithiins. The photoelectron spectra of 1,2-dithiin and 1,2-diselenin contain a sharp ionization that corresponds to removal of an electron from an orbital that is predominantly chalcogen-chalcogen σ bonding in character. The narrow ionization profile indicates fairly weak chalcogen-chalcogen σ bonding in this orbital, which would result in a corresponding weakly antibonding chalcogen-chalcogen σ* orbital. Computational results show that an orbital that is primarily S-S σ* in character is the lowest unoccupied molecular orbital of 1,2-dithiin, and electronic transition calculations show a low-energy HOMO-to-LUMO transition that can be described as a π/lone pair- to-σ* transition that explains the unusual color of 1,2-dichalcogenins.
• Glass, R. S., & Jouikov, V. V. (1999). Electrochemical electrophilic aromatic methylthiation in liquid SO₂. Tetrahedron Letters, 40(35), 6357-6358.
  More info

  Abstract: Controlled potential electrolysis of dimethyldisulfide in liquid sulfur dioxide provides a strongly electrophilic methylthiating agent. This species methylthiates strongly to weakly activated arenes in good to excellent yield.
• Stowasser, R., Glass, R. S., & Hoffmann, R. (1999). The dithiacyclooctane cation (DTCO⁺): Conformational analysis, interconversion barriers and bonding. Journal of the Chemical Society. Perkin Transactions 2, 1559-1561.
  More info

  Abstract: A theoretical conformation analysis of the dithiacyclooctane radical cation (DTCO+) suggests that the lowest energy conformer is a chair-boat, with a partial but significant S-S σ bond. For the ring flip process of this molecule we calculate a barrier of 40 kJ mol-1 and two possible pathways: one involves a boat-boat conformer and an untwisted transition structure, the other a chair-chair conformer and a twisted transition structure.
• Bojkova, N. V., & Glass, R. S. (1998). Synthesis and characterization of tetrathiatetraasterane. Tetrahedron Letters, 39(50), 9125-9126.
  More info

  Abstract: Irradiation of 1,4-dithiin gives the cis, syn, cis-photodimer in 70-80% yield whose structure has been unequivocally established by X-ray crystallographic methods. A minor product is formed in this photodimerization which is shown to the trans, anti, trans-photodimer by X-ray structural analysis. Irradiation of the syn photodimer produces tetrathiatetraasterane in 70% yield. The structure of this product is also proven by X-ray methods.
• Y., N., Ordóñez, M., Juaristi, E., & Glass, R. S. (1998). Conformational energy of the (η⁵-cyclopentadienyl) iron(II) dicarbonyl group. Journal of Organic Chemistry, 63(24), 8935-8937.
  More info

  Abstract: The conformational energy of the (η5-cyclopentadienyl) iron(II) dicarbonyl group was determined by variable-temperature 1H NMR spectroscopic studies on cis-4-phenyl-1-(η5-cyclopentadienyl) iron(II) dicarbonyl cyclohexane. This is the first determination of the A-value of a group with a transition metal directly attached to a cyclohexane ring. The stereospecific synthesis of cis- and trans-4-phenyl-1-(η5-cyclopentadienyl) iron(II) dicarbonyl cyclohexane and cis- and trans-4-tert-butyl-1-(η5- cyclopentadienyl) iron(II) dicarbonyl cyclohexane and the X-ray crystal structure of cis-4-tert-butyl-1-(η5-cyclopentadienyl) iron(II) dicarbonyl cyclohexane are reported.
• Block, E., Glass, R. S., DeOrazio, R., Lichtenberger, D. L., Pollard, J. R., Russell, E. E., Schroeder, T. B., Thiruvazhi, M., & Toscano, P. J. (1997). Significant intramolecular sulfur-sulfur interactions in cis- and trans-2,3-dimethyl-5,6-dithiabicyclo-[2.1.1]hexane. Synlett, 525-528.
  More info

  Abstract: Reduction of (±)-(1α, 2α, 3β, 4α, 5β)-2,3-dimethyl-5,6-dithiabicyclo[2.1.1]hexane 5-oxide (3a) and (1α, 2α, 3α, 4α, 5β)-2,3-dimethyl-5,6-dithiabicyclo[2.1.1]hexane 5-oxide (3b) gives the bis-sulfides (±)-trans-2,3-dimethyl-5,6-dithiabicyclo[2.1.1]hexane (2a) and cis-2,3-dimethyl-5,6-dithiabicyclo[2.1.1]hexane (2b), respectively. Bis-sulfides 2a and 2b, on oxidation with one equivalent of m-CPBA, give 3a and 3b, respectively, as the only products. Significant sulfur-sulfur interactions in 2a and 2b are indicated by the long-wavelength UV maxima, the lowered ionization potentials, as measured by photoelectron spectroscopy, and the lowered oxidation potentials, as found by cyclic voltammetry.
• Drouin, B. J., Gruhn, N. E., Madden, J. F., Kukolich, S. G., Barfield, M., & Glass, R. S. (1997). Gas-phase conformational analysis of 1,4,7-trithiacyclononane. Journal of Physical Chemistry A, 101(48), 9180-9184.
  More info

  Abstract: Conformational analysis of 1,4,7-trithiacyclononane, [9]aneS 3, in the gas phase was done using three techniques: ab initio molecular orbital calculations at the UF and MP2 levels as well as microwave and photoelectron spectroscopies. The photoelectron spectroscopic data show evidence for at least two conformations with different ionization energies. Using the calculated photoelectron spectra, the observed sulfur 3p ionization peaks can be assigned to C 1 and C 2 conformations. Forty of the observed microwave transitions can be assigned to a C 1 symmetry, asymmetric top, rigid rotor spectrum with rotational constants A = 1155.651(3) MHz, B = 998.442(3) MHz, and C = 629.426(2) MHz. Additional microwave lines are believed to be due to a nonrigid C 2 symmetry conformation. No significant populations of conformers of higher symmetry are found.
• Glass, R. S. (1997). Aspects of organoselenium chemistry. Paediatric and Perinatal Drug Therapy, 1(2), 159-174.
  More info

  Abstract: Monoselenophosphate, SePO3H3-nn-, has been chemically synthesized and characterized. It has been shown to be identical with the biological selenium donor SePX. Hydrolysis of selenophosphate is pH dependent and maximal at about pH 7. The dianion is the species which hydrolyzes fastest. The hydrolysis occurs via a dissociative monomeric metaphosphate-like transition state. Alcohols and amines are phosphorylated by monoselenophosphate. The sensitivity of detection of both 77Se and 125Te by NMR spectroscopy has been greatly increased by inverse proton detection using multiple-quantum 1H-{77Se} and 1H-{125Te} correlation spectroscopy. One- and two-dimensional HMQC spectra have been obtained for a variety of organoselenium and tellurium compounds. The signal enhancement obtained by such methods are comparable to the theoretical values. © 1998 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint.
• Glass, R. S., Guo, Q., & Liu, Y. (1997). Neighboring the effect in the oxidation of α-Stannyl phenyl vinyl sulfides. Tetrahedron, 53(36), 12273-12286.
  More info

  Abstract: α-Stannyl vinyl sulfides were generally prepared by hydrostannylation of thioacetylenes catalyzed by Pd(PPh3)4. The regio- and stereochemistry of the products was determined unequivocally in three cases by X-ray crystallographic structure studies and in the others by 1H NMR spectroscopic analysis. The irreversible oxidation potentials of these compounds were determined in acetonitrile and dichloromethane by cyclic voltammetry. The oxidation potentials provide evidence for significant interaction between the C-Sn σ band and sulfur 3p lone pair orbital in cases with appropriate geometry.
• Glass, R. S., Pollard, J. R., Schroeder, T. B., Lichtenberger, D. L., Block, E., DeOrazio, R., Guo, C., & Thiruvazhi, M. (1997). Spectroscopic, theoretical, and electrochemical studies of 1,2-dithiins. Phosphorus, Sulfur and Silicon and Related Elements, 120-121, 439-440.
  More info

  Abstract: The lowest oxidation potentials for 1,2-dithiins are in the range of 0.67-0.96 V in acetonitrile and 0.81-1.04 V in dichloromethane. These oxidation potentials are less anodic than expected based on the ionization potentials of 1,2-dithiin determined by photoelectron spectroscopy. Theoretical calculations suggest that the reason for this difference is a change in optimized geometry between 1,2-dithiin and its oxidized species.
• Kamiński, R., Glass, R. S., Schroeder, T. B., Michalski, J., & Skowrońska, A. (1997). Monoselenophosphate: Its hydrolysis and its ability to phosphorylate alcohols and amines. Bioorganic Chemistry, 25(4), 247-259.
  More info

  Abstract: The rate of hydrolysis of monoselenophosphate, the labile selenium donor compound required for the synthesis of selenium-dependent enzymes and seleno-tRNAs, was determined by 31P NMR spectroscopy. The rate depended on the pH of the solution and was maximal at a pH ~7. This suggests that the dianion is the species that reacts fastest. Added alcohols and amines do not significantly affect the rate of hydrolysis but are phosphorylated. The entropy of activation is positive for the hydrolysis of monoselenophosphate. These data suggest a dissociative in nature mechanism for the hydrolysis of monoselenophosphate involving a monomeric metaphosphate-like transition state in the rate-determining step.
• Knothe, G., Glass, R. S., Schroeder, T. B., Bagby, M. O., & Weisleder, D. (1997). Reaction of isolated double bonds with selenium dioxide/hydrogen peroxide: Formation of novel selenite esters. Synthesis, 57-60.
  More info

  Abstract: The reaction of the SeO2/H2O2 system with long-chain olefinic compounds was investigated. The products sequence is epoxides → selenite esters → vicinal diols (threo diastereomers). Structure elucidation of the novel selenite esters by NMR studies including 77Se-NMR and lanthanide shift experiments showed that they are a mixture of cis/trans isomers. The SeO2/H2O2 system thus presents a novel possibility for the synthesis of selenites.
• Liu, Y., & Glass, R. S. (1997). Direct deprotonation of aliphatic sulfides. Tetrahedron Letters, 38(50), 8615-8618.
  More info

  Abstract: Alkylmethyl sulfides are regioselectively deprotonated by n-butyllithium and potassium tert-butoxide at the methyl group in good yields. Thiolane and thiane are deprotonated under the same conditions at the α-position in good yield.
• Sanaullah, ., Hungerbühler, H., Schöneich, C., Morton, M., G., D., Wilson, G. S., Asmus, K., & Glass, R. S. (1997). Electron-transfer-coupled ligand dynamics in Cu(I/II)(TTCN)₂ complexes in aqueous solution. Journal of the American Chemical Society, 119(9), 2134-2145.
  More info

  Abstract: One-electron oxidation of copper(I) bis(1,4,7-trithiacyclononane), [Cu(I)(TTCN-κ3)(TTCN-κ1)]+, 1, a coordination complex with a tetrahedral CuS4 core, to [Cu(II)(TTCN-κ3)2]2+, 2, with an octahedral CuS6 core, has been studied by pulse radiolysis and electrochemistry in aqueous solution at various pH values. In addition to the geometry change about the metal ion in this oxidation, the nonchelating 1,4,7-trithiacyclononane (TTCN) ligand in 1 changes conformation on becoming chelated in 2. However, pulse radiolysis reveals that this process does not occur intramolecularly but affords a bimolecular reaction in which the oxidized copper incorporates an external TTCN. Evidence for this mechanism is drawn from corresponding experiments with a variety of related Cu(I) complexes in which the monodentate TTCN has been replaced by other sulfur-containing ligands and which have been structurally characterized by X-ray crystallography. From all these studies it is concluded that oxidation of 1 and all these other complexes of Cu(I) is accompanied by immediate loss of the monodentate ligand generating [Cu(II)(TTCN-κ3)(H2O)3]2+, 3. Transient 3 is characterized by an optical absorption with λ(max) = 370 nm and ε ~ 2000 M-1 cm-1 which depends on pH because this transient participates in three acid/base equilibria. Deprotonation of the three water ligands associated with Cu(II) results in increasingly blue-shifted absorptions. Undeprotonated transient 3 prevails at pH ≤ 6, and converts directly into the stable Cu(II) complex 2 via reaction with an unoxidized molecule of 1 or free TTCN. The corresponding bimolecular rate constants are 5.2 (± 0.5) x 105 and 8.4 (± 1.0) x 105 M-1 s-1, respectively. For the deprotonated forms of 3 this process is increasingly slowed down and at higher pH (≤ 9) the formation of 2 is completely prevented. The formation of transient 3 is also consistent with the pH dependence of the electrochemistry of 1. Under electrochemical conditions the conversion into 2 follows first-order kinetics due to a relatively high TTCN concentration available near the electrode surface after oxidation of 1. All the results require rapid ligand exchange in 1 and a particularly labile monodentate TTCN ligand. This has been corroborated by 1H NMR spectroscopic studies on 1.
• Schroeder, T. B., Job, C., Brown, M. F., Glass, R. S., You, N., & Block, E. (1997). ¹H-{¹²⁵Te} indirect detection in nuclear magnetic resonance spectra of organotellurium compounds. Magnetic Resonance in Chemistry, 35(11), 752-756.
  More info

  Abstract: 125Te was measured by inverse proton detection using multiple-quantum 1H-{125Te} correlation spectroscopy. One- and two-dimensional heteronuclear multiple quantum coherence (HMQC) experiments are reported for dimethyl telluride, dimethyl ditelluride, benzyl tellurocyanate, trimethyltelluronium chloride, telluromethionine, tellurophene, 1,4-thiatellurin and di(n-butyl) telluride having a range of 125Te-1H coupling constants from 14.6 to 102.5 Hz. The enhancement for indirect vs. direct 125Te detection was estimated for trimethyltelluronium chloride. The theoretical enhancement is 50.7 and that estimated experimentally 46.2. Multiple-quantum 1H-{123Te} correlation spectroscopy is also illustrated for one example. © 1997 John Wiley & Sons, Ltd.
• Glass, R. S. (1996). Interaction between functional groups and its consequences in oxidation of thioethers. Reviews on Heteroatom Chemistry, 15, 1-24.
  More info

  Abstract: Factors which affect the oxidation and ionization potentials of thioethers and the lifetimes of sulfur cation radicals have been investigated. Neighboring sulfur participation lowers the oxidation potential of thioethers and neighboring oxygen stabilizes sulfur cation radicals by S-O bond formation. The oxidation and ionization potentials of 1,3-dithiane are reduced by 2-stannyl groups due to interaction of the C-Sn bond with the sulfur 3p lone pair orbitals. Annulation of a naphthalene ring to 1,5-dithiocane increases lone pair-lone pair interaction lowering its ionization potential but not its oxidation potential.
• Glass, R. S., Radspinner, A. M., & Singh, W. P. (1996). Sulfur cation radicals. Pure and Applied Chemistry, 68(4), 853-858.
  More info

  Abstract: The oxidation potentials of 2-silylated and 2-stannylated 1,3-dithianes have been determined by cyclic voltammetry. There is substantial, geometry-dependent, lowering of the oxidation potential by tin substituants as illustrated by 2,2-bis(trimethylstannyl)-1,3-dithiane whose oxidation potential of 0.19V is almost IV lower than that of 1,3-dithiane itself. The UV He I photoelectron spectrum of this compound shows that its two lowest ionization potentials of 7.48 and 7.97 eV are about 1 eV lower than those of 1,3-dithiane. X-ray crystallographic structure studies on 2,2-bis(trimethylstannyl)-1,3-dithiane reveal that it adopts a chair conformation with an axial and an equatorial tin substituent. Variable temperature 13C NMR spectroscopic studies demonstrate that this compound undergoes ring inversion in solution with a barrier of approximately 13.5 kcal/mol.
• Glass, R. S. (1995). Cation radicals of organosulphur compounds. Xenobiotica, 25(7), 637-651.
  More info

  PMID: 7483663;Abstract: 1. Biological and biomimetic oxidations of thioethers are reviewed. 2. γ-Radiolysis, pulse radiolysis, photochemical, chemical, and electrochemical methods for generating sulphur cation radicals are discussed and exemplified. 3. The major reactions of sulphur cation radicals: nucleophilic attack, electron transfer, decnrboxylation, reaction with O2, C-S, C-C, and α-C-M bond cleavages, sulphur abstraction, and rearrangements are presented.
• Glass, R. S., & Stadtman, T. C. (1995). Selenophosphate.. Methods in Enzymology, 252, 309-315.
  More info

  PMID: 7476367;
• Glass, R. S., & Stadtman, T. C. (1995). [31] Selenophosphate. Methods in Enzymology, 252, 283-292.
• Glass, R. S., & Jung, W. (1994). Stereospecific conrotatory ring opening of a tetraaryl thiirane cation radical. Journal of the American Chemical Society, 116(3), 1137-1138.
• Glass, R. S., & Liu, Y. (1994). Diastereoselective oxidation of substituted 1,2-dithiolan-3-ones. Tetrahedron Letters, 35(23), 3887-3888.
  More info

  Abstract: Oxidation of 1,2-dithiolan-3-ones 1 with one equivalent of dimethyldioxirane in dichloromethane at -78°C produces the corresponding 1,2-dithiolan-3-one 1-oxides 2 in high yield and with diastereoselectivities as high as 18:1. The major diastereomer formed is the trans isomer. An X-ray crystallographic structure study of the major diastereomer 2c obtained by oxidation of 1g is reported. © 1994.
• Glass, R. S., Singh, W. P., & Hay, B. A. (1994). Diastereoselective oxidation of substituted thietanes and stereoselective oxidation of their sulfoxides. Tetrahedron Letters, 35(32), 5809-5812.
  More info

  Abstract: Oxidation of substituted thietanes 1a, b, and 6 with m-chloroperoxybenzoic acid preferentially gives the corresponding cis-sulfoxides with modest diastereoselectivity. Selective oxidation of the trans over the cis diastereomeric pairs of sulfoxides 2a, 3a; 2b, 3b; 7, 8 occurs with moderate selectivity with m-chloroperoxybenzoic acid. The basis for these selectivities is hydrogen bonding between the 3-substituent and the peracid. © 1994.
• Sanaullah, ., Wilson, G. S., & Glass, R. S. (1994). The effect of pH and complexation of amino acid functionality on the redox chemistry of methionine and X-Ray structure of [Co(en)₂(L-Met)](ClO₄)₂.H₂O. Journal of Inorganic Biochemistry, 55(2), 87-99.
  More info

  PMID: 8051543;Abstract: Anodic oxidation of methionine under different pH conditions is reported. The results are compared with the oxidation process when the glycinic terminus of methionine is coordinated with Co(III). Synthesis of [Co(en)2(L-Met)](ClO4)2, [Co(trien)(L-Met)](CF3SO3)2, and [Co(trien)(OSO2CF3)2]CF3SO3 is reported where L-Met = L-methionine, en = ethylenediamine, trien = triethylenetetraamine. The triflato complex ([Co(trien)(OSO2CF3)2]CF3SO3) can serve as a starting material for synthesizing a variety of complexes. The x-ray structure of [Co(en)2(L-Met)](ClO4)2.H2O is also presented The complex crystallizes in space group P21 of the mono-clinic system with two independent molecules in the crystallographic asymmetric unit. The unit cell dimensions are a = 9.582 (2) Å, b = 11.554 (2) Å, c = 19.988 (6) Å, and f = 98.85 (2)°. The two molecular units are related by a pseudo-center of symmetry. The electrochemical data presented here suggest a major role of the neighboring group and pH in defining the ease of oxidation of methionine. © 1994.
• Glass, R. S. (1993). Monoselenophosphate: Synthesis, characterization, and identity with the prokaryotic biological selenium donor, compound SePX. Biochemistry®, 12555-12559.
  More info

  PMID: 8251472;Abstract: A labile, selenium donor compound required for synthesis of selenium-dependent enzymes and seleno-tRN As is formed from ATP and selenide by the SELD enzyme. This compound, tentatively identified as a selenophosphate [Veres, Z., Tsai, L., Scholz, T. D., Politino, M., Balaban, R. S., & Stadtman, T. C. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 2975-2979], is indistinguishable from chemically prepared monoselenophosphate by 31P NMR spectroscopy and ion pairing HPLC. Furthermore, addition of chemically prepared monoselenophosphate caused a dose-dependent decrease in the amount of 75Se incorporated into tRNAs from 75SePX generated in situ by SELD enzyme. A procedure is described for the chemical synthesis of monoselenophosphate in which the readily prepared (MeO)3PSe is converted in quantitative yield to (TMSO)3PSe followed by complete cleavage of the latter to monoselenophosphate in oxygen-free aqueous buffer. The chemical properties of chemically synthesized monoselenophosphate are described. © 1993 American Chemical Society.
• Glass, R. S., Steffen, L., Swanson, D. D., Wilson, G. S., Gelder, R. d., A.G., R., & Reedijk, J. (1993). Bis(trithiacyclononane)metal(II) compounds and Jahn-Teller distortions from octahedral geometry, electrochemistry, spectroscopy, and crystal structures of the copper bis(tetrafluoroborate) bis(acetonitrile) complex at 177 K and the cadmium bis(tetrafluoroborate) and copper bis(tetrafluoroborate) bis(nitromethane) complexes at 300 K. Inorganica Chimica Acta, 207(2), 241-252.
  More info

  Abstract: The structures and the EPR spectra are described of compounds with formula M(ttcn)2(A)2, with ABF4-; MCu, Cd, Fe and the Cu(II)-doped Cd(II) and Fe(II) compounds. Single crystal structures are described for the copper compound Cu(ttcn)2(BF4)2(MeCN)2 (1) at low temperature, and for the cadmium compound Cd(ttcn)2(BF4)2(MeNO2)2 (2) and copper compound Cu(ttcn)2(BF4)2(MeNO2)2 (3) at room temperature. Compound 1 crystallizes in the space group P21/c with a=20.695(2), b=14.944(1), c=8.864(1) Å, β=90.797(8)° and Z=4. The unit cell contains two crystallographically independent Cu ions, each at a crystallographic inversion center, which are structurally almost identical. The copper ion with the CuS62+ chromophore appears to be nearly octahedral, just as found earlier for the room temperature structure. Relevant Cu-S distances are for Cu(A): 2.407, 2.419 and 2.458 and for Cu(B): 2.407, 2.428 and 2.461 Å. Compound 2 also crystallized in the space group P21/c with a=10.314(2), b=15.138(2), c=9.461(2) Å, β=99.39(1)° and Z=2. The Cd(II) ion is octahedrally surrounded by six S atoms at almost equal distances varying from 2.649 to 2.663 Å. Compound 3 crystallizes in the space group Pbca with a=19.746(2), b=15.422(2), c=9.227(1) Å and Z=4. The copper ion occupies a crystallographic inversion center. The copper ion is significantly distorted from an octahedral arrangement of the six coordinated sulfur atoms with Cu-S distances ranging from 2.343(2) to 2.504(2) Å. Cyclic voltammetric studies on Cu(ttcn)22+ in aqueous buffer at pH 3 show a reversible one-electron reduction with Eo'=0.408(1) V versus AgCl/Ag reference. EPR spectra were recorded of the pure copper compound acetonitrile solvate, as well as of Cu(II) dopes in the isomorphous Fe(II) and Cd(II) compounds. The results indicate that in the case of the undiluted copper compound only a single signal (g=2.06) is observed even down to 4 K, thereby not providing any evidence of a Jahn-Teller splitting. However, Cu(II) dopes in the isomorphous, diamagnetic Fe(II) compound show anisotropic signals below 100 K, with values for g∥ and g⊥ of 2.113 and 2.027, respectively (A∥=153 G). At room temperature a complex spectrum of isotropic and anisotropic lines is observed. Dopes in the corresponding Cd compounds show well-resolved spectra, with parameters similar to the Fe(II)-doped species. Heat capacity measurements on compound 3 show no phase transition in the temperature range 1.2-300 K. Such measurements on compound 1 show phase transitions near 90 and 150 K. © 1993.
• Sanaullah, ., Kano, K., Glass, R. S., & Wilson, G. S. (1993). Chemical and electrochemical investigation of redox-associated conformational changes in the bis(1,4,7-trithiacyclononane)copper(II/I) system and x-ray structure of the copper(I) complex. Journal of the American Chemical Society, 115(2), 592-600.
  More info

  Abstract: Extensive electrochemical measurements of the kinetic parameters for electron transfer in aqueous bis(1,4,7-trithiacyclononane)copper(II) ([CuII(TTCN)2]) and its Cu(I) analog have been carried out at a glassy carbon electrode. Our studies have shown that the [CuII(TTCN)2]/[CuI(TTCN)2] system follows an ECEC square mechanism rather than just simple electron transfer as suggested previously. Unlike the octahedral Cu(II) complex [Cu(TTCN)2]PF6 crystallizes with two independent formula units in space group P21/n of the monoclinic system with unit cell dimensions a = 8.608 (3) Å, b = 31.041 (8) Å, c = 16.008 (4) Å, and β= 90.88 (2)°. The two molecular units have distorted tetrahedral CuS4 coordination spheres with monodentate and tridentate TTCN ligands. The mondentate ligands have a unique conformation for the TTCN moiety with Cu(I) coordinated differently in each of the two independent [CuI(TTCN)2] units. The ring conformation, however, remains the same. The uncoordinated sulfur atoms on the monodentate TTCN ligand can coordinate to a metal ion added to the solution, and this ligand ultimately reverts to a tridentate ligand with the standard endodentate [3 3 3] conformation of the TTCN moiety. The transient trinuclear complex with added Cu(II) can be detected both electrochemically and spectrophotometrically. Electrochemical oxidation of [CuI(TTCN)2] and reduction of [CuII(TTCN)2] both occur rapidly, but in both cases, the electron transfer is followed by chemical steps. These chemical steps are the conformational reorganization of the monodentate TTCN ligand into the tridentate [3 3 3] conformer and the reverse of this process respectively. Digital simulations of the cyclic voltammetric data for the kinetic parameters of both the [CuII(TTCN)2]/[CuI(TTCN)2] system and the entire mechanism of the interaction between [CuI(TTCN)2] and Cu(II) followed by the subsequent reduction of the intermediate have been carried out.
• Glass, R. S., Broeker, J. L., Anklam, E., & Asmus, K. (1992). Formation of sulfur-centered cation radicals by photofragmentation. Tetrahedron Letters, 33(13), 1721-1724.
  More info

  Abstract: The selected dialkyl dithioethers 1,5-dithiocane, 1,4-dithiepane, 1,4-dithiane, and 2,6-dithiaheptane are readily monoalkylated in nitromethane by tert-butyl O-trifluoromethanesulfonyl-3-hydroxyperoxypropanoate, 6, to give the corresponding sulfonium salt peresters 2a-c, and 3 in good yield. Laser flash photolysis of these compounds affords the known two-sulfur, three-electron stabilized cation radicals 2a, b, and 5 which were characterized by optical absorption spectroscopy. © 1992.
• Glass, R. S., Radspinner, A. M., & Singh, W. P. (1992). Neighboring tin effect in electron transfer from thioethers. Journal of the American Chemical Society, 114(12), 4921-4923.
• Glass, R. S., Sabahi, M., & Singh, W. P. (1992). A new synthesis of 2-substituted 6-endo-(methylthio)bicyclo[2.2.1]heptanes. Synthesis and crystal and molecular structure of a conformationally restricted methionine analogue. Journal of Organic Chemistry, 57(9), 2683-2688.
  More info

  Abstract: A new and advantageous synthesis of 2-endo-substituted-6-endo-(methylthio)bicyclo[2.2.1]heptanes, especially suitable for the preparation of such compounds with 2-endo-hydroxy and amino substituents, is presented. Also reported is the synthesis of the conformationally restricted methionine analogue (±)-2-endo-amino-6-endo-(methylthio)bicyclo[2.2.1]heptane-2-exo- carboxylic acid and its crystal and molecular structure determined by X-ray crystallographic techniques. © 1992 American Chemical Society.
• Glass, R. S., & Broeker, J. L. (1991). Conformationai analysis of naphtho[1,8-b,c]-1,5-dithiocin and its s-oxides in solution. Tetrahedron, 47(28), 5087-5098.
  More info

  Abstract: The conformation and conformational barriers In dithioether 1: naphtho(1,8-b,c]-1,5-dithiocin were determined in solution by 1H and 13C NMR spectroscopic analysis and AMl semiempirical computations. In solution the chair conformer of dithloether 1 is 0.6 kcal/mol lower in energy than the boat conformer. The barriers for chair-to-chair ring inversion and chair-to-boat conversion in this compound are 8.9 kcal/mol and 7.9 kcal/mol, respectively. Monosulfone 3, disulfoxide 4, and sulfoxide-sulfone 5, adopt the chair conformation in solution in contrast to their boat conformation in the solid state. In solution the chair conformation for 3-5 with equatorial sulfoxides is more stable than either the chair conformation with axial sulfoxides or the boat conformers by at least 1 kcal/mol. The barrier for chair-to-chair ring inversion for monosulfone 3 has been determined to be 10.8 kcal/mol. In solution, disulfone 6 appears to adopt either a boat or chair conformation in contrast to the twist conformation in the solid state. The maximum barrier for ring inversion of 6 is 7 kcal/mol. New evidence for the geometry of the transition state for the ring inversion is presented. © 1991.
• Glass, R. S., & Broeker, J. L. (1991). Synthesis, crystal, and molecular structures and conformations of naphthot[1,8-b,c]-1,5-dithiocin-1,1-dioxide,-1,5-dioxide,-1,1,5-trioxide and -1.1,5,5-Tetraoxide. Tetrahedron, 47(28), 5077-5086.
  More info

  Abstract: Chemoselective oxidation of the known naphtho[1,8,-b,c-1,5-dithiocin, dithioether 1, to the corresponding -1,1-dioxide: monosulfone 3, 1,5-dioxide: cis-disulfoxide 4, or -1,1,5,5-tetraoxide: disulfone 6 can be accomplished with potassium permanganate and a phase transfer catalyst in a two phase system in 66% yield, with sodium metaperiodate in aqueous methanol in 95% yield, or ruthenium tetraoxide in 70% yield, respectively. Oxidation of the known monosulfoxide 2 with potassium permanganate and a phase transfer catalyst in a two phase system also gave monosulfone 3 in 73% yield. The corresponding -1,1,5-trioxide: sulfoxide-sulfone 5 was selectively prepared in quantitative yield by oxidation of the monosulfone 3 with sodium metaperiodate in aqueous methanol. The crystal and molecular structures, and conformations of naphtho[1,8-b,c]-1,5-dithiocin-1,1-dioxide (3), -1,5-dioxide (4), -1,1,5-trioxide (5), and -1,1,5,5-tetraoxide (6) were determined by single crystal X-ray analysis. These compounds crystallize in the monoclinic space group P21/c with a=13.184(4)Å, b=13.182(5)Å, c=7.106(l)Å, β=104.14(5)°, and Z=4, the orthorhombic space group Pbca, with a=17.931(2)Å, b=13.108(3)Å, c=20.280(4)Å, and Z=16, the monoclinic space group P21/n with a=9.298(1)Å, b=10.264 (2)Å, c=13.396(2)Å, β=110.06(1)°, and Z=4, and the orthorhombic space group Pbca with a=12.258(3)Å, b=9.997Å, C=20.168Å, and 2-8, respectively. The structures were solved by direct methods. Full-matrix least-squares refinement led to conventional R factors of 0.034, 0.046, 0.041, and 0.049, respectively. The conformations of the molecules in the solid state were distorted boat, boat with cis-dlequatorial sulfoxide; boat with equatorial sulfoxide, and the unusual twist conformer, respectively. © 1991.
• Steffen, L. K., Glass, R. S., Sabahi, M., Wilson, G. S., Schöneich, C., Mahling, S., & Asmus, K. (1991). ^•OH Radical Induced Decarboxylation of Amino Acids. Decarboxylation vs Bond Formation in Radical Intermediates. Journal of the American Chemical Society, 113(6), 2141-2145.
  More info

  Abstract: The •OH radical reaction with exo-2-amino-endo-6-(methylthio)bicyclo[2.2.1]heptane-endo-2-carboxylic acid primarily affords oxidation of the sulfur center in the molecule. The subsequent pathway strongly depends on pH. A transient radical with interaction between the sulfur and the carboxylate moieties is stabilized particularly in acid solutions with maximum yield at pH 3. It is characterized by a sulfur-carboxyl bond, which exhibits typical features of 2σ/1σ* three-electron bonds. It exhibits an optical absorption (λmax 340 nm) and decays with t1/2 ≈ 26 μs via deprotonation to an α-thioalkyl carbon-centered radical. This transient bond formation between the carboxyl group and the oxidized sulfur at low pH successfully prevents a competing process, namely, decarboxylation, which takes over at pH > 4. The underlying mechanism is considered to be a concerted action involving an electron transfer from the anionic carboxylate to the oxidized sulfur atom, homolytic carbon-carboxyl bond breakage, and deprotonation of the amino group. Related studies indicate that this kind of radical-induced decarboxylation can be generalized and receives its driving force to a significant extent from the resonance stabilization of the α-amino radical remaining after CO2 cleavage.
• Glass, R. S., Broeker, J. L., & Firouzabadi, H. (1990). Stereochemistry of the formation and hydrolysis of a dithioether dication. Journal of Organic Chemistry, 55(22), 5739-5746.
  More info

  Abstract: Naphtho[1,8-bc]-1,5-dithiocin 1-oxide (7) was prepared by oxidation of naphtho[1,8-6c]-1,5-dithiocin with sodium metaperiodate in aqueous methanol. The structure and conformation of sulfoxide 7 in the solid state was unequivocally established to be boat 7A with equatorial sulfoxide by X-ray crystallographic analysis. Sulfoxide 7 crystallizes in the triclinic space group P1 (no. 2) with a = 8.959 (2), b = 11.313(3), and c = 12.975 (3) Å, α = 64.98 (2)°; β = 81.18 (2)°, γ = 78.67 (2)°, and Z = 4. The structure was solved by direct methods. Full-matrix least-squares refinement led to a conventional R factor of 0.040 after several cycles of anisotropic refinement. Dissolution of sulfoxide 7 in concentrated sulfuric acid produces disulfide dication 8, which on hydrolysis regenerates the sulfoxide. Deprotonation of sulfoxide 7 with methyllithium followed by treatment with D2O stereoselectively gives monodeuterated sulfoxide 7 (X = D). 1H NMR spectroscopic analysis of sulfoxide 7 (X = H) revealed that it is predominantly in chair conformation 7B with equatorial sulfoxide and the deuterium atom in the monodeuterated derivative is predominantly axial (7B, Ha = D). Disulfide dication 8 is deduced to be predominantly in boat conformation 8A by 1H NMR spectroscopic analysis and that derived from monodeuterated sulfoxide 7 has the deuterium predominantly axial (8A, Hb = D). Hydrolysis of the deuterated disulfide dication regenerates sulfoxide 7 with the deuterium axial. These surprising stereochemical results require retention of configuration at the sulfoxide sulfur both in the formation of disulfide dication 8 and its hydrolysis. © 1990 American Chemical Society.
• Glass, R. S., Hojjatie, M., Sabahi, M., Steffen, L. K., & Wilson, G. S. (1990). Synthesis and crystal and molecular structure of the conformationally restricted methionine analogue (±)-2-exo-amino-6-endo-(methylthio)bicyclo[2.2.1]heptane-2-endo- carboxylic acid and neighboring group participation in its anodic oxidation. Journal of Organic Chemistry, 55(12), 3797-3804.
  More info

  Abstract: (±)-2-exo-Amino-6-endo-(methylthio)bicyclo[2.2.1]heptane-2-endo- carboxylic acid (1c) was synthesized by amination of the lithium enolate of methyl 6-endo-(methylthio)bicyclo[2.2.1]heptane-2-endo-carboxylate with O-(mesitylenesulfonyl)hydroxylamine followed by hydrolysis. Its crystal and molecular structure was determined by single-crystal X-ray analysis. It crystallizes in the monoclinic space group P21/c with a = 9.681 (6) Å, b = 10.276 (5) Å, c = 9.773 (4) Å, β = 91.23 (4)°, and Z = 4. The structure was solved by direct methods. Full-matrix least-squares refinement led to a conventional R factor of 0.048 after several cycles of anisotropic refinement. The structure is compared both with 6-exo-(methylthio)bicyclo[2.2.1]heptane-2-endo-carboxylic acid (3) and the HBr salt of 2-exo-aminobicyclo[2.2.1]heptane-2-endo-carboxylic acid (2). Electrochemical oxidation of 1c in acetonitrile, using the technique of cyclic voltammetry, revealed two oxidation waves with peak potentials of 0.90 and 1.35 V. Controlled potential electrolysis of 1c provided the corresponding sulfoxides as a mixture of diastereomers (in 60 and 25-30% yield, respectively), which were also prepared by chemical oxidation, derivatized, separated, and characterized. The remarkable cathodic shift of 450 mV for 1c is ascribed to neighboring carboxylate participation in oxidation of the thioether moiety. © 1990 American Chemical Society.
• Juaristi, E., Gordillo, B., Sabahi, M., & Glass, R. S. (1990). Conformational analysis of 5-substituted 1,3-dioxanes. 2. Phenylthio and cyclohexylthio groups and their sulfinyl and sulfonyl derivatives. Journal of Organic Chemistry, 55(1), 33-38.
  More info

  Abstract: The positions of equilibrium, established by acid catalysis, between diastereomeric cis- and trans-5-(phenylthio)-(7), 5-(phenylsulfinyl)- (8), 5-(phenylsulfonyl)- (9), 5-(cyclohexylthio)- (10), 5-(cyclohexylsulfinyl)- (11), and 5-(cyclohexylsulfonyl)-2-tert-butyl-1,3-dioxanes (12) are reported and compared with published data for the 5-(methylthio)- (1), 5-(methylsulfinyl)- (2), 5-(methylsulfonyl)- (3), 5-(tert-butylthio)- (4), 5-(tert-butylsulfinyl)-(5), and 5-(tert-butylsulfonyl)-2-isopropyl-1,3-dioxanes (6). Although ΔG° values for sulfides 1, 4, and 7 are very similar, there exist significant differences in the conformational behavior of the sulfoxides and the sulfones, which result from the relative steric, electrostatic, and torsional effects arising from each substituent. The information at hand (1H and 13C NMR spectroscopic data, X-ray crystallographic analysis, etc.) shows that, while sulfone cis-6 has the S-tert-butyl group outside the ring, with both sulfonyl oxygens above the dioxane ring and eclipsing the endocyclic C-C bonds, the alkyl and aryl substituents in cis-3, cis-9, and cis-12 point inside the ring. The phenylsulfonyl-inside rotamer in cis-9 leads to steric and electron/electron repulsion that overcomes the electrostatic attractive interactions between the (negative) endocyclic oxygens and the (positive) sulfur in the sulfonyl group, so that equatorial trans-9 predominates at equilibrium, ΔG° = -0.44 kcal/mol. All sulfoxides place both the sulfinyl oxygen and the substituent outside the dioxane ring. © 1990 American Chemical Society.
• Glass, R. S., Andruski, S. W., Broeker, J. L., Firouzabadi, H., Steffen, L. K., & Wilson, G. S. (1989). Sulfur-sulfur lone pair and sulfur-naphthalene interactions in naphtho[1,8-b,c]-1,5-dithiocin. Journal of the American Chemical Society, 111(11), 4036-4045.
  More info

  Abstract: Naphtho[1,8-b,c]-1,5-dithiocin (4), which has a unique geometry so constrained that the sulfur atoms are held close to one another and oriented such that their p orbitals are almost colinear and orthogonal to the naphthalene π-system, has been synthesized. Its crystal and molecular structure was determined by single-crystal X-ray analysis. It crystallizes in the orthorhombic space group Pbca with a = 8.140 (2) Å, b = 9.866 (1) Å, c = 28.302 (3) Å, and Z = 8. The structure was solved by direct methods. Full-matrix least-squares refinement led to a conventional R factor of 0.046 after several cycles of anisotropic refinement. For comparison purposes the crystal and molecular structure of the previously reported 1,8-bis-(methylthio)naphthalene (5) was also determined by X-ray techniques. Semiempirical molecular orbital methods (MNDO and AM1) were used to analyze the five highest occupied molecular orbitals in 1,8-bis(methylthio)naphthalene as a function of the C(1)-S and C(8)-S torsion angles and to analyze the molecular orbitals of compound 4. Of particular interest is the result that the energy of the highest occupied molecular orbital in 1,8-bis(methylthio)naphthalene is nearly independent of the C-S torsion angle and that the lowest ionization potential for 4 is predicted to be 7.75 eV and its lone pair-lone pair splitting due to transannular S-S interaction is 1.6-2.0 eV. The computations were correlated with the experimentally measured He I and He II photoelectron spectra of 4 and the AM1 method provided reasonable agreement with the experimental data. The electrochemical oxidation of 4 and 5 in acetonitrile was studied by cyclic voltammetry. They undergo irreversible oxidation with peak potentials of 0.70 and 0.47 V, respectively, versus a Ag/0.1 M AgNO3 in acetonitrile reference electrode. Controlled-potential electrolysis of 4 gives the corresponding sulfoxide (12), which is consistent with removal of an electron from the highest occupied molecular orbital which is sulfur lone pair in character. © 1989 American Chemical Society.
• Glass, R. S., Broeker, J. L., & Jatcko, M. E. (1989). Distinguishihg ionization from sulfur p-type lone pair orbitals and carbon π-molecular orbitals by he I/He II photoelectron spectroscopy. Tetrahedron, 45(5), 1263-1272.
  More info

  Abstract: He I and He II photoelectron spectra of methylthiomethylbenzene (2), 2-(1-nethylethylthio) ethylbenzene (3), 1-naphthalenemethanethiol (4), 1,1-dimethylethylthiobenzene (5), benzenethiol (6), and methylthiobenzene (7) are reported. Comparison of the He I and He II band areas for each compound provide a reliable basis for assigning the bands as due to photoionization from a carbon π-molecular orbital, sulfur p-type lone pair orbital, or mixed orbital.Ionization from a molecular orbital localized on sulfur results in a large decrease in intensity using He II compared with He I as the source relative to ionization from carbon π-molecular orbitals. Mixed orbitals with both sulfur and carbon character also give rise to diminished intensities in the He II versus He I spectra relative to pure carbon orbitais, but proportionately less decrease than pure sulfur orbitais. © 1989.
• Glass, R. S., Farooqui, F., Sabahi, M., & Ehler, K. W. (1989). Formation of thiocarbonyl compounds in the reaction of Ebselen oxide with thiols. Journal of Organic Chemistry, 54(5), 1092-1097.
  More info

  Abstract: Reaction of α-toluenethiol with Ebselen oxide, 2, affords dibenzyl disulfide and seleno sulfide 5, R = PhCH2. In the course of this reaction, thiobenzaldehyde is formed and can be trapped with cyclopentadiene in 90% yield. Reaction of 2-propene-1-thiol with 2 afforded thioacrolein dimer in 69% yield and seleno sulfide 5, R = CH2-CH=CH2. Trapping, stereochemical, and isotopic exchange studies were used to determine if in the reaction of 2 with 1-heptanethiol, cyclohexanethiol, and N-acetyl-D,L-cysteine thiocarbonyl compounds heptanethial, cyclohexanethione, and 2-acetamino-3-thioxopropanoic acid (α-thioformyl-N-acetylglycine), respectively, are also formed. These studies showed that free thiocarbonyl compounds are not formed in these reactions. © 1989 American Chemical Society.
• Wright, M. E., Hoover, J. F., Glass, R. S., & Day, V. W. (1989). Investigation of complexes of the type η⁵-C₅H₅Fe(CO)₂(η¹-C₅H₄X) (X = CH₃, CONHTs). Crystal and molecular structure of 5-[η⁵-C₅H₅Fe(CO)₂]-1-[TsNHCO]cyclopentadiene. Journal of Organometallic Chemistry, 364(3), 373-379.
  More info

  Abstract: The new complex Fp(η1-C5H4CH3) (2) was prepared and its fluxionality studied. Complex 2 was found to have a higher energy barrier for the fluxional process than the related systems Fp(η1-C5H5), η5-C5Me5Fe(CO)2(η1-C5H5), and Fp(η1-C5H4CONHTs) (3). Reaction of 2 with dimethyl acetylenedicarboxylate gave a mixture of two cycloadducts where the methyl-group was found in the 5- and the 1-position in a ratio of 3 1, respectively. In both cycloadducts the Fp moiety was found regio- and stereoselectively in the 7-position and anti to the carboxylate groups. The molecular structure of crystalline 3 was determined and showed that the CONHTs substituent of the η1-ring was in the 1-position. © 1989.
• Engel, P. S., Gerth, D. B., Keys, D. E., Scholz, J. N., Houk, K. K., Rozeboom, M. D., Eaton, T. A., Glass, R. S., & Broeker, J. L. (1988). Ionization potentials of some azoalkanes by photoelectron spectroscopy. Tetrahedron, 44(22), 6811-6814.
  More info

  Abstract: Photoelectron spectra have been obtained for a set of azo compounds consisting of three pairs of cis, trans isomers, seven bridgehead substituted 2,3-diazabicyclo[2.2.2]oct-2-enes (DBO's), and one arylazoalkane. The lowest ionization potentials, which range from 7.83 to 9.21 eV, do not correlate with cis ground state energy or photolability of the DBO derivatives. Vibrational fine structure was observed in three DBO's, allowing verification that the lowest ionization takes place from the antibonding combination of nitrogen lone pairs. © 1988.
• Glass, R. S., Petsom, A., Hojjatie, M., Coleman, B. R., Duchek, J. R., Klug, J., & Wilson, G. S. (1988). Facilitation of electrochemical oxidation of dialkyl sulfides appended with neighboring carboxylate and alcohol groups. Journal of the American Chemical Society, 110(14), 4772-4778.
  More info

  Abstract: The electrochemical oxidation of variously 2-substituted 6-(methylthio)bicyclo[2.2.1]heptanes in acetonitrile was studied by using cyclic voltammetry. Three compounds, endo acid salt 1h, endo primary alcohol 1c, and endo tertiary alcohol 1g, were found to oxidize much more easily in the presence of trace amounts of bromide ion. Controlled potential electrolysis of endo acid salt 1h in the presence of 2,6-di-tert-butylpyridine and a small amount of water gave endo acid sulfoxide 5a. Such oxidation in the presence of 18O-labeled water led to the incorporation of the label into the oxygen atoms of both the sulfoxide and carboxylate moieties of endo acid sulfoxide 5a. This result suggested the intermediacy of acyloxysulfonium salt 6. This salt was prepared by bromine oxidation of endo acid salt 1h at low temperatures, characterized spectroscopically, and hydrolyzed to endo acid sulfoxide 5a. Controlled potential electrolysis of endo primary alcohol 1c and endo tertiary alcohol 1g in the presence of 2,6-di-tert-butylpyridine produced the corresponding alkoxysulfonium salts 7a and 7b, respectively. These data are interpreted in terms of bromide catalysis of the thioether oxidation with neighboring carboxylate or alcohol participation. © 1988 American Chemical Society.
• Juaristi, E., Cruz-Sanchez, J. S., Petsom, A., & Glass, R. S. (1988). Conformational preference of the s=O group.3. Continued evidence for a very strong s-s=o anomeric interaction from the nmr spectroscopic study of 44,5,5-tetramethyl-1,2-dithiane 1-oxide¹ 1 For Part 2,see: Juaristi, E.; Cruz-Sánchez, J.S. J. Org. Chem. in press.. Tetrahedron, 44(18), 5653-5660.
  More info

  Abstract: The 1H and 13C NMR behavior of the title compound (4) was studied in order to determine the conformational preference of the S=O group in this heterocycle. The NMR spectra were assigned by a combination of homo- and heteronuclear double irradiation, as well as nuclear Overhauser enhancement experiments. From the results of variable temperature, solvent effects and shift reagent experiments, it is concluded that the axial conformer dominates the equilibrium to such an extent that no contribution of the equatorial isomer is recorded. This result suggest that ΔG° (4-ax 4-eq)≥ 1.7 kcal mol, and because the axial conformer suffers from a syn-diaxial Me/S=O interaction, a ΔG° ≥ 3.0 kcal mol for the conformational equilibrium in the parent 1,2-dithiane mono-S-oxide (1) can be extrapolated. Some discussion of the possible mechanism responsible for such strong anomeric effect is presented. © 1988.
• Mahling, S., Asmus, K., Glass, R. S., Hojjatie, M., Sabahi, M., & Wilson, G. S. (1988). Erratum: Neighboring group participation in radicals: Pulse radiolysis studies on radicals with sulfur-oxygen interaction (Journal of Organic Chemistry (1987) 52, (3717)). Journal of Organic Chemistry, 53(21), 5192-.
• Glass, R. S., Petsom, A., & Wilson, G. S. (1987). Diastereoselective oxidations of a thioether appended with a neighboring carboxylic acid group. Journal of Organic Chemistry, 52(16), 3537-3541.
  More info

  Abstract: Diastereoselective oxidations of endo acid 5a, 6-endo-(methylthio)bicyclo[2.2.1]heptane-2-endo-carboxylic acid, and endo ester 5b, methyl 6-endo-(methylthio)bicyclo[2.2.1]heptane-2-erado-carboxylate, with the bromine complex of 1,4-diazabicyclo[2.2.2]octane in aqueous acetic acid to the corresponding sulfoxides are reported. The relative stereochemistry of the major diastereomeric product obtained by such oxidation of endo acid 5a was unequivocally established by X-ray crystallographic analysis. Endo acid sulfoxide 7a crystallizes in the monoclinic space group P21/c with a = 8.554 (1) Å, b = 8.989 (2) Å, c = 12.575 (2) Å, β = 98.64 (1)°, and Z = 4. The structure was solved by direct methods. Full-matrix least-squares refinement led to a conventional R factor of 0.038 after several cycles of anisotropic refinement. The predominant sulfoxide formed in the oxidation of endo acid 5a and endo ester 5b with the bromine complex of 1,4-diazabicyclo[2.2.2]octane is of the opposite diastereomeric series. This difference in stereochemistry is ascribed to neighboring-group participation in the oxidation of endo acid 5a by the carboxylate moiety. Diastereoselective oxidations of endo acid 5a and endo ester 5b with m-chloroperoxybenzoic acid to the corresponding sulfoxides are reported. The results suggest that the carboxylic acid group does not direct attack by the peracid on the thioether. © 1987 American Chemical Society.
• Glass, R. S., Sabahi, M., Hojjatie, M., & Wilson, G. S. (1987). Isolation and crystal and molecular structures of two geometric isomers of a 3N,2S-pentacoordinate copper(II) complex [4]. Inorganic Chemistry, 26(14), 2194-2196.
• Juaristi, E., Martínez, R., Méndez, R., Toscano, R. A., Soriano-García, M., Eliel, E. L., Petsom, A., & Glass, R. S. (1987). Conformational analysis of 1,3-dioxanes with sulfide, sulfoxide, and sulfone substitution at C(5). Finding an eclipsed conformation in cis-2-tert -butyl-5-(tert-butylsulfonyl)-1,3-dioxane. Journal of Organic Chemistry, 52(17), 3806-3811.
  More info

  Abstract: The positions of equilibrium, established by acid catalysis, between diastereomeric cis- and trans-5-(tert-butylthio)- (1), 5-(tert-butylsulfinyl)- (2), and 5-(tert-butylsulfonyl)-2-isopropyl-1,3-dioxanes (3) are reported and compared with previously published data for the 5-methylthio (4), 5-methylsulfinyl (5), and 5-methylsulfonyl (6) analogues. Although ΔG° values for the sulfides 1 and 4 are very similar, the difference in conformational behavior for sulfoxides 2 and 5 is significant, and the effect of changing from methyl to tert-butyl in the sulfones (6 → 3) is quite dramatic: the large preference of the methyl analogue for the axial position (1.19 kcal/mol) is reversed in 3 where the equatorial isomer is more stable by 1.14 kcal/mol. The conformational behavior in 1-6 is discussed in terms of the rotamer population of the axial isomer, in which steric and electrostatic effects are dominant. X-ray crystallographic data on cis-2-tert-butyl-5-(tert-butylsulfonyl)-1,3-dioxane (cis-9, axial sulfonyl) show that the S-tert-butyl group is outside the ring, with both sulfonyl oxygens above the dioxane ring and eclipsing the endocyclic C-C bonds. The electrochemical behavior of cis-1 and trans-1 supports the idea that lone-pair/lone-pair electron repulsion is responsible for the large predominance of the equatorial isomer. © 1987 American Chemical Society.
• Mahling, S., Asmus, K., Glass, R. S., Hojjatie, M., & Wilson, G. S. (1987). Neighboring group participation in radicals: Pulse radiolysis studies on radicals with sulfur-oxygen interaction. Journal of Organic Chemistry, 52(17), 3717-3724.
  More info

  Abstract: Neighboring group participation by alcohol and carboxylate groups resulting in kinetic and thermodynamic stabilization of an oxidized sulfur atom in various organic sulfides is reported. The resulting radical intermediates of the general type (-S↔O)• are characterized by an optical absorption in the 400-nm range and exhibit lifetimes of up to several hundred microseconds in aqueous solution under pulse radiolysis conditions. Significant sulfur-oxygen interaction seems to occur, however, only if both heteroatoms are separated by three or four carbon atoms in the unoxidized molecule which enables favorable five- or six-membered ring structures in the radical intermediates. This geometric effect can additionally be favored by minimizing the free rotation of the functional groups through rigid molecular structures, e.g., in norbornane derivatives, and introduction of particular substituants. A most suitable function for stabilization of an oxidized sulfur atom seems to be a carboxylate group where an overall neutral radical of the general structure -S•+↔-OOC is formed. In these species stabilization can be envisaged to involve the carboxylate group as a whole rather than only an individual oxygen atom. The bond strength of the sulfur-carboxylate interaction is estimated to be of the order of 50 kJ mol-1 as deduced from the temperature dependence of its dissociation. Further evidence for net sulfur-carboxylate bonding is provided by rate constants of 105-107 M-1 s-1 for its proton-assisted decay. These rates are considerably lower than for the diffusion controlled protonation of free carboxylate functions. Oxidation of endo-2-(2-hydroxyisopropyl)-endo-6-(methylthio)bicyclo[2.2.1]heptane yields a transient where sulfur-oxygen interaction is associated with a strong acidification of the alcoholic hydroxyl group. A pK = 5.9 has been measured for the (-S↔OH)•+ ⇄ (-S↔O)• + H+ equilibrium. All the results on these transient radical intermediates can be viewed in terms of neighboring group participation. Such participation is also clearly evidenced in the formation and properties of intermolecular radical cations, (R2S∴SR2)+, derived from these sulfides, and in the kinetics of the primary oxidation process. Absolute rate constants for the one-electron oxidation of various sulfides by CCl3OO• radicals, for example, have been found to range from 3 × 108 to
• Glass, R. S., Hojjatie, M., Setzer, W. N., & Wilson, G. S. (1986). Stereoselective synthesis, structural studies, and hydrolysis of tricyclic alkoxysulfonium salts. Journal of Organic Chemistry, 51(10), 1815-1820.
  More info

  Abstract: The crystal and molecular structure of endo tertiary alcohol 1b determined by X-ray crystallographic techniques is reported. The molecule crystallizes in the space group P21/n with a = 14.628 (7) Å, 6 = 5.648 (1) Å, c = 14.973 (8) Å, β = 113.78 (4)°, Z = 4. This structure features an unsymmetrical contra twist of the norbornyl skeleton and an intramolecular hydrogen bond between the sulfur atom and hydroxyl group with a very short distance of 3.119 Å. IR spectroscopic studies provide evidence for this intramolecular hydrogen bond in dilute solutions of endo tertiary alcohol 1b but not in endo primary alcohol 1a. Treatment of endo primary alcohol 1a and endo tertiary alcohol 1b with tert-butyl hypochlorite followed by mercury(II) chloride provides the corresponding alkoxysulfonium salts 2a and 2b, respectively. The crystal and molecular structures of these salts were determined by single-crystal X-ray studies. These salts crystallize in the space groups P21/c and P1, respectively, with a = 10.152 (3) Å, b = 11.857 (4) Å, c = 12.087 (3) Å, β = 97.98 (2)°, Z = 4, and a = 8.416 (3) Å, b = 9.678 (3) Å, c = 10.688 (4) Å, β = 87.72 (3)°, Z = 2, respectively. Both structures feature short S-O bond lengths of 1.58 (1) Å and 1.587 (4) Å, respectively, and large S-O-C (8) bond angles of 121.2 (9)° and 124.0 (3)°, respectively. Base hydrolysis of these salts produces the corresponding sulfoxides 11a and 11b by nucleophilic attack by hydroxide ion on sulfur. © 1986 American Chemical Society.
• Glass, R. S., McConnell, W. W., & Andruski, S. W. (1986). (η⁵-C₅H₅)Fe(CO)₂(η ¹-C₅H₅). A useful synthetic equivalent of 5-amino-1,3-cyclopentadiene in cycloaddition reactions. Journal of Organic Chemistry, 51(26), 5123-5127.
  More info

  Abstract: Diels-Alder reactions of 5-amino-1,3-cyclopentadiene have not been reported, and other stereoselective, high-yield routes to substituted bicyclo[2.2.1]hept-2-en-7-syn-amines are limited. This paper reports use of (η5-C6H5)Fe-(CO)2(η 1-C5H5) (1) as a synthetic equivalent of 5-amino-1,3-cyclopentadiene in cycloaddition reactions. The previously reported cycloadducts of 1 and alkenes were treated with ammonium cerium(IV) nitrate, bromine, or chlorine in acetonitrile containing sodium azide to give the corresponding acyl azides in which the CON3 group replaced the (η5-C5H5)Fe(CO)2 group with retention of stereochemistry in good yield. Thermal Curtius rearrangement of these acyl azides proceeded stereospecifically in excellent yield. This regioselective and stereoselective sequence provides a useful route to substituted 7-syn-amino-2-norbornenes. © 1986 American Chemical Society.
• Glass, R. S., Petsom, A., Wilson, G. S., Martínez, R., & Juaristi, E. (1986). Electrosynthesis of 1,2-dithiolane 1-oxides from substituted 1,3-dithianes. Journal of Organic Chemistry, 51(23), 4337-4342.
  More info

  Abstract: Controlled potential oxidation of a variety of 5-substituted 2-tert-butyl-1,3-dithianes in wet acetonitrile, using an undivided electrochemical cell, provide 4-substituted 1,2-dithiolane 1-oxides selectively and in good yields. Adsorption to the electrode surface of the platinum anode, rendering it passive in the electrolysis of these sulfur-containing compounds is a solvable problem. Although acid-sensitive O-trimethylsilyl ethers are cleaved under the reaction conditions, O-tert-butyldimethylsilyl ethers only suffer cleavage to a modest extent, and an ethylene ketal moiety suffers little, if any, cleavage. © 1986 American Chemical Society.
• Juaristi, E., López-Núñez, N. A., Glass, R. S., Petsom, A., Hutchins, R. O., & Stercho, J. P. (1986). The conformational preference of the diphenylphosphinoyl group in cyclohexane. Journal of Organic Chemistry, 51(8), 1357-1360.
• Wilson, G. S., Swanson, D. D., & Glass, R. S. (1986). Cobalt(II) bis(1,4,7-trithiacyclononane): A low-spin octahedral complex. Inorganic Chemistry, 25(21), 3827-3829.
  More info

  Abstract: Cobalt(II) forms a bis complex with 1,4,7-trithiacyclononane (1,4,7-TTCN) with an unprecedentedly large overall formation constant of 8 × 1013. This complex has an effective magnetic susceptibility of 1.71 μB. Thus, this is a low-spin octahedral Co(II) complex, and such complexes are exceedingly rare. Cyclic voltammetry of Co(1,4,7-TTCN)22+ shows three diffusion-controlled one-electron steps at 0.573, -0.292, and -0.998 V vs. SHE corresponding to Co(III)/Co(II), Co(II)/Co(I), and Co(I)/Co(0) reductions, respectively. The unique properties of this complex are suggested to be due to ligand conformational control. © 1986 American Chemical Society.
• Wright, M. E., Nelson, G. O., & Glass, R. S. (1985). Preparation, crystal structure, and low-temperature ¹H NMR study of (η⁵-C₅Me₅)Fe(CO)₂(η ¹-C₅H₅). Reaction of (η⁵-C₅R₅)Fe(CO)₂(η ¹-C₅H₅) (R = Me, H) with bis(trifluoromethyl)ketene. Organometallics, 4(2), 245-250.
  More info

  Abstract: Sequential reaction of (η5-C5Me5)Fe(CO)2I with silver tetrafluoroborate, cyclopentadiene, and finally triethylamine affords the new compound (η5-C5Me5)Fe(CO)2(η 1-C5H5) (2) in 75% yield. Reaction of 2 with dimethyl fumarate in dichloromethane gives the [3 + 2] cycloadduct dimethyl 7-syn-[(η5-C5Me5)Fe-(CO) 2]bicyclo[2.2.1]hept-5-ene-2-endo,3-exo-dicarboxylate in 90% yield. Competitive cycloaddition of the η1-C5H5 moiety in (η5-C5H5)Fe(CO)2(η 1-C5H5) (1) and 2 with dimethyl fumarate reveals 2 to be ca. 5 times more reactive. Reaction of 1 and 2 with bis(trifluoromethyl)ketene produces the unexpected and unique 2:1 adducts [(η5-C5R5)Fe(CO) 2]{1,3-bis[(CF3)2CHCO]cyclopentedienyl} (4, R = H; 5, R = Me). The molecular and crystal structure for 2 is presented. Complex 2 crystallizes in the monoclinic space group P21/n with a = 8.591 (2) Å, b = 36.347 (13) Å, c = 10.119 (3) Å, β = 92.71 (2)°, and Z = 8. The structural parameters are refined to convergence with R1 = 0.063 and R2 = 0.084 for 2563 reflections having I > 3σ(I). A low-temperature 1H NMR study reveals that the η1-C5H5 ligand in 2 possesses increased fluxionality relative to analogue 1. The increased fluxionality of the η1-C5H5 ring in 2 is attributed to a combination of electronic and steric differences of the η5-C5Me5 ligand relative to the η5-C5H5 group. © 1985 American Chemical Society.
• Glass, R. S., & McConnell, W. W. (1984). Concerted [4π + 2π] cycloaddition of (η⁵-C₅H₅)Fe(CO)₂(η ¹-C₅H₅) with the isomeric 2-butenedinitriles. Organometallics, 3(11), 1630-1632.
  More info

  Abstract: Fumaronitrile and maleonitrile rapidly cycloadd to (η5-C5H5)Fe(CO)2(η 1-C5H5) with comparable rates to afford 7-syn-[(η5-C5H5)Fe(CO) 2]bicyclo[2.2.1]hept-5-ene-2-exo,3-endo-dicarbonitrile (3b) and a 1:1 mixture of 7-syn-[(η5-C5H5)Fe(CO) 2]bicyclo[2.2.1]hept-5-ene-2-exo,3-exo-dicarbonitrile (3c) and 7-syn-[(η5-C5H5)Fe(CO) 2]bicyclo[2.2.1]hept-5-ene-2-endo,3-endo-dicarbonitrile (3d), respectively, in excellent yield. Mechanistic studies strongly support a concerted [4π + 2π] cycloaddition for these reactions. © 1984 American Chemical Society.
• Glass, R. S., Hojjatie, M., Wilson, G. S., Mahling, S., Göbi, M., & Asmus, K. (1984). Pulse radiolysis generation of sulfur radical cations stabilized by neighboring carboxylate and alcohol groups. Journal of the American Chemical Society, 106(18), 5382-5383.
• Glass, R. S., Reineke, K., & Shanklin, M. (1984). Diels-Alder reactions of S-vinyl-S-arylsulfoximines. Journal of Organic Chemistry, 49(9), 1527-1533.
  More info

  Abstract: Cyclopentadiene and the known S-p-tolyl-S-vinyl-N-phthalimidosulfoximine (1a) undergo Diels-Alder reaction to give a mixture of cycloadducts in excellent yield. The structures of the cycloadducts including stereochemistry are assigned by 1H NMR spectroscopy. The crystal and molecular structure of the major cycloadduct 5d, n = 1, G = 1,2-C6H4(CO)2N was determined unequivocally by X-ray crystallographic techniques. Treatment of this major cycloadduct with hydrazine in ethanol resulted in conversion of the sulfoximine to sulfoxide group concomitant with reduction of the carbon-carbon double bond. Use of allyl alcohol as solvent in this reaction allowed conversion to the corresponding unsaturated sulfoxide 8. The previously unknown S-p-tolyl-S-vinyl-N-(p-tolylsulfonyl)-sulfoximine (1b) is somewhat more reactive than phenyl vinyl sulfone and undergoes Diels-Alder reactions with cyclic and acyclic 1,3-dienes in 81-95% yield. The endo selectivity of vinylsulfoximine 1b is 9:2 with cyclopentadiene and 93:7 with 1,3-cyclohexadiene. With 2-methyl-1,3-butadiene the para adduct is produced regioselectively in a ratio of 4:1. Although formation of the endo adducts from vinylsulfoximine 1b and cyclopentadiene and 1,3-cyclohexadiene is not diastereoselective, the diastereomers can be separated by HPLC. The cycloadducts from 1,3-cyclohexadiene and vinylsulfoximine 1b have been converted to bicyclo[2.2.2]oct-2-ene and bicyclo-[2.2.2]oct-2-en-5-one. © 1984 American Chemical Society.
• Juaristi, E., Guzmán, J., Kane, V. V., & Glass, R. S. (1984). Conformational przferknce of the S→O bond. ¹H and ¹³C NMR studies of the mono-S-oxides of 1,2-, 1,3- and 1,4-dithianes. Tetrahedron, 40(9), 1477-1485.
  More info

  Abstract: The 1H and 13C NMR behavior of the monosulfoxides of 1,2-, 1,3-and 1,4-dithianes (1-3) were studied in order to determine the conformational preference of the S→O bond in these heterocycles. From the results of variable temperature, double irradiation, solvent effects and shift reagent experiments, It is concluded that the axial conformers dominate the conformational equilibria of 1 and 3. On the other hand, 2-equatorial is more stable than 2-axial by 0.64 kcal/mol (ΔG°) at -80°, in CD3OD. This value is essentially identical with the one determined in CHClF2, and the lack of a solvent effect appears to indicate that dipole/dipole interactions do not control this equilibrium. AΔGc‡ = 11.0 kcal/mol was determined for the inversion process of 2. Complete 1H and 13C NMR assignments for 1-3 are presented. © 1984.
• Wright, M. E., Hoover, J. F., Nelson, G. O., Scott, C. P., & Glass, R. S. (1984). (η⁵-C₅H₅)Fe(CO)₂(η ¹-C₅H₅). A useful synthetic equivalent of methyl 1,3-cyclopentadiene-5-carboxylate in cycloaddition reactions. Journal of Organic Chemistry, 49(17), 3059-3063.
  More info

  Abstract: A variety of activated unsaturated compounds, including acrylonitrile, react with Fp(η1-C5H5), where Fp = (η5-C5H5)Fe(CO)2, to give cycloadducts in good yield. Diethylchloroalane facilitates these cycloadditions and even methyl acrylate cycloadds in good yield in the presence of this Lewis acid. These reactions all occur regio-and stereoselectively to afford syn-7-Fp cycloadducts exclusively. The stereochemistry at C(2) and C(3) is selective in some cases but not in others. Stereospecific replacement of the Fp moiety in these cycloadducts by a CO2Me group with retention of configuration occurs in good yield by oxidation with ammonium cerium(IV) nitrate in carbon monoxide saturated methanol. This two-step sequence, cycloaddition followed by oxidation, renders Fp(η1-C5H5) a synthetic equivalent of methyl 1,3-cyclopentadiene-5-carboxylate in cycloaddition reactions. © 1984 American Chemical Society.
• Glass, R. S., Coleman, B. R., Setzer, W. N., & Wilson, G. S. (1983). NEIGHBORING GROUP PARTICIPATION IN ELECTRON TRANSFER FROM DIALKYL THIOETHERS.. Electrochemical Society Extended Abstracts, 83-1, 977-.
• Setzer, W. N., Ogle, C. A., Wilson, G. S., & Glass, R. S. (1983). 1,4,7-Trithiacyclononane, a novel tridentate thioether ligand, and the structures of its nickel(II), cobalt(II), and copper(II) complexes. Inorganic Chemistry, 22(2), 266-271.
  More info

  Abstract: An improved method for preparing 1,4,7-trithiacyclononane (1,4,7-TTCN) is reported. The yields of certain medium-sized-ring dithioethers are also improved by this method. The bis(1,4,7-trithiacyclononane)nickel(II), -cobalt(II), and -copper(II) complexes have been prepared and their structures determined by X-ray crystallographic analyses. The [Ni(1,4,7-TTCN)2](BF4)2 complex crystallizes in the monoclinic space group P21/c with a = 8.681 (2) Å, b = 11.685 (3) Å, c = 11 624 (3) Å, β = 106.57 (2)°, and Z = 2. The [Co(1,4,7-TTCN)2](BF4)2 complex crystallizes in the orthorhombic space group Pbca with a = 19.789 (40) Å, b = 15.235 (12) Å, c = 9.202 (3) Å, and Z = 4. The [Cu(1,4,7-TTCN)2](BF4)2 complex crystallizes in the orthorhombic space group Pbca with a = 21.169 (3) Å, b = 15.193 (2) Å, c = 8.729 (2) Å, and Z = 4. Full-matrix least-squares refinement led to convergence with R = 0.030, 0.094, and 0.062, respectively, after several cycles of anisotropic refinement. In each complex the metal atom occupies a slightly distorted octahedral environment of sulfur atoms provided by two facially coordinating 1,4,7-TTCN ligands. The geometrical constraints of the ligand induce nearly regular octahedral coordination even with copper(II). © 1983 American Chemical Society.
• Glass, R. S., Coleman, B. R., Devi, U., Setzer, W. N., & Wilson, G. S. (1982). Synthesis, characterization, and anodic oxidation of selected norbornyl dithioethers. Journal of Organic Chemistry, 47(14), 2761-2764.
  More info

  Abstract: Both 2-exo- and 2-endo-[(methylthio)methyl]-6-endo-(methylthio)bicyclo[2.2.1]heptane (1a and 2a, respectively) were prepared by standard methods. Treatment of episulfide 3 with sulfur dichloride followed by reduction and alkylation afforded 2-endo,6-endo-bis(methylthio)-3-exo,5-exo-dichlorobicyclo[2.2.1]heptane (2d). The structure of 2d was unequivocally established by X-ray crystallographic analysis. An interesting feature of the structure of 2d is the unusually short S⋯S nonbonded distance of 3.179 (1) Å. Electrochemical oxidation of 1a, 2a, and 2d was studied by using cyclic voltammetric and rotating-disk techniques. Anodic oxidation of 2a is almost 600 mV easier than that of its isomer la because of intramolecular interaction between the two sulfur atoms in 2a but not 1a on oxidation. The vertical ionization potentials for the nonbonding sulfur 3p lone-pair electrons were determined by photoelectron spectroscopy for 1a, 2a, and 2d. © 1982 American Chemical Society.
• Glass, R. S., Setzer, W. N., Devi, U., & Wilson, G. S. (1982). Highly diastereoselective oxidations of a thioether appended with a neighboring hydroxyl group. Tetrahedron Letters, 23(23), 2335-2338.
  More info

  Abstract: Highly diastereoselective oxidations of endo-alcohol 1 to the corresponding sulfoxides, the relative stereochemistries of these sulfoxides and that of an intermediary alkoxysulfonium salt determined by X-ray crystallographic analysis is reported. © 1982.
• Ryan, M. D., Swanson, D. D., Glass, R. S., & Wilson, G. S. (1981). Studies of the EE mechanism. Evidence for reversible dimer formation in electrochemical oxidation of a cyclic dithioether. Journal of Physical Chemistry, 85(8), 1069-1075.
  More info

  Abstract: The electrochemical oxidation of 1,5-dithiacyclooctane (DTCO) in acetonitrile has been shown to result in two closely spaced (ΔE ≈ 20 mV) reversible one-electron-transfer steps. A reversible second-order chemical reaction is observed to follow production of the cation radical thus resulting in dimer formation. As the dimer is not electroactive at the potential of the initial process, its further oxidation or reduction must be preceded by dissociation. These conclusions are supported by cyclic voltammetry, controlled potential electrolysis, rotating disk electrode studies, and semiintegral analysis. The unusual ease of the second electron-transfer step is attributed to interactions between the two mesocyclic sulfur atoms. © 1981 American Chemical Society.
• Setzer, W. N., Coleman, B. R., Wilson, G. S., & Glass, R. S. (1981). Conformational analysis of mesocyclic polythioethers. Gas phase conformational analysis of five mesocyclic polythioethers using photoelectron spectroscopy. Tetrahedron, 37(16), 2743-2747.
  More info

  Abstract: The helium I photoelectron spectra of the mesocyclic polythioethers 1,4-dithiacycloheptane (1,4-DTCH), 1,5-dithiacyclooctane (1,5-DTCO), 1,5-dithiacyclononane (1,5-DTCN), 1,4,7-trithiacyclononane (1,4,7-TTCN), and 1,6-dithiacyclodecane (1,6-DTCD) are reported. The conformations of these molecules in the gas phase are deduced from correlations of the observed spectra with semi-empirical MO calculations, as well as molecular mechanics analysis. © 1981.
• Setzer, W. N., Wilson, G. S., & Glass, R. S. (1981). Conformational analysis of mesocyclic polythioethers. Crystal and molecular structures of 1,4-dithiacycloheptane, 1,5-dithiacyclononane and 1,6-dithiacyclodecane. Tetrahedron, 37(16), 2735-2742.
  More info

  Abstract: The crystal and molecular structures of 1,4-dithiacycloheptane (1,4-DTCH), 1,5-dithiacyclononane (1,5-DTCN), and 1,6-dithiacyclodecane (1,6-DTCD) have been determined by single crystal X-ray studies. These compounds crystallize in the space groups P212121 (No. 19), P21/c (No. 14), and P21/n, respectively with a = 5.409(1), b = 10.883(2), c = 11.390(2) Å, Z = 4; a = 9.600(4), b = 12.378(8), c = 7.904(3) Å, /gb = 113.31(3)°, Z = 4; and a = 5.290(1), b = 12.853(3), c = 6.850(2) Å, β = 93.39(2)°, Z = 2, respectively. The nonhydrogen atoms were located using direct methods and the hydrogen atoms were found by Fourier difference maps. Full-matrix least-squares refinement led to conventional R factors of 0.0459, 0.0558 and 0.0314, respectively. The conformations adopted by 1,4-DTCH, 1,5-DTCN and 1,6-DTCD, in the crystalline slate, are twist chair (C2 symmetry), twist boat chair (C2 symmetry), and boat chair boat (C2k symmetry), respectively. The transannular S-S distances are 3.583, 4.108 and 4.864 Å, respectively. © 1981.
• Glass, R. S., Deardorff, D. R., & Henegar, K. (1980). Highly stereoselective reductions of α-alkoxy-β-keto esters. Aspects of the mechanism of sodium borohydride reduction of ketones in 2-propanol. Tetrahedron Letters, 21(26), 2467-2470.
  More info

  Abstract: Reduction of α-alkoxy-β-keto esters with sodium borohydride in 2-propanol proceeds with high stereoselectivity via a five-membered ring chelated sodium ion. © 1980.
• Glass, R. S., Duchek, J. R., Devi, U., Setzer, W. N., & Wilson, G. S. (1980). Synthesis and characterization of 2-substituted 6-(methylthio)bicyclo[2.2.1]heptanes. Journal of Organic Chemistry, 45(18), 3640-3646.
  More info

  Abstract: The synthesis and structure elucidations of several 2-endo-substituted-6-endo-(methylthio)-, 2-exo-substituted-6-endo-(methylthio)-, 2-endo-substituted-6-exo-(methylthio)-, and 2-exo-substituted-6-exo-(methylthio)-bicyclo[2.2.1]heptanes, 2-5, respectively, are reported. The structure proofs involved a combination of spectroscopic, X-ray crystallographic, and equilibration studies. The crystal and molecular structures of 6-endo-(methylthio)bicyclo[2.2.1]heptane-2-endo-carboxylic acid (2a) and 6-exo-(methylthio)bicyclo[2.2.1]heptane-2-endo-carboxylic acid (4a) were determined by X-ray crystallographic techniques. These compounds crystallize in the space groups Pbca and P21/n, respectively, with a = 13.040 (2) Å, b = 10.877 (3) Å, c = 13.518 (3) Å, Z = 8, and a = 12.740 (2) Å, b = 6.200 (1) Å, c = 13.146 (2) Å, β = 114.81 (1)°, Z = 4, respectively. The nonhydrogen atoms were located in each case by direct methods. Full-matrix least-squares refinement led to conventional R factors of 0.0466 and 0.0389, respectively, after several cycles of anisotropic refinement. These molecular structure determinations revealed an unsymmetrical contra twist of the norbornyl skeleton in endo acid 2a and an unsymmetrical synchro twist in endo acid 4a. © 1980 American Chemical Society.
• Glass, R. S., Wilson, G. S., & Setzer, W. N. (1980). Crystal and molecular structure of 1,4,7-trithiacyclononane. Journal of the American Chemical Society, 102(15), 5068-5069.
  More info

  Abstract: The crystal and molecular structure of 1,4,7-trithiacyclononane has been determined from a single-crystal X-ray study. The compound crystallizes in the rhombohedral space group R3c with six molecules per unit cell of dimensions (hexagonal axes) a = b = 12.584 (3), c = 9.209 (2) Å. The observed and calculated densities are 1.41 (1) and 1.42 g cm-3, respectively. Full-matrix least-squares refinement using 252 unique reflections having 4° ≤ 2 θ ≤ 50° and I ≥ 3σ(I) converged at R = 0.0217 and Rw = 0.0285. The compound exists, in the crystalline state, in the C3 conformation with the sulfur atoms endodentate. The transannular S-S distance is 3.45 Å. © 1980 American Chemical Society.
• Wilson, G. S., Swanson, D. D., Klug, J. T., Glass, R. S., Ryan, M. D., & Musker, W. K. (1979). Electrochemical oxidation of some mesocyclic dithioethers and related compounds [8]. Journal of the American Chemical Society, 101(4), 1040-1042.
• Glass, R. S., & Swedo, R. J. (1978). Nucleophilic substitution reactions of N-alkyldi(trifluoromethane)sulfonimides. Role of the solvent hexamethylphosphoric triamide. Journal of Organic Chemistry, 43(11), 2291-2294.
• Glass, R. S., Deardorff, D. R., & Gains, L. H. (1978). Pyrrolizidine synthesis by intramolecular cyclization of a substituted azacyclooctane-4,5-oxide. Tetrahedron Letters, 19(33), 2965-2968.
• Glass, R. S., Herzog, J. D., & Sobczak, R. L. (1978). Preparation and reactions of 5-alkylpentachloro-1,3-cyclopentadienes. Application to sesquiterpene synthesis. Journal of Organic Chemistry, 43(16), 3209-3214.
  More info

  Abstract: A variety of 5-alkyl-1,2,3,4,5-pentachloro-1,3-cyclopentadienes (4a-d) were prepared. The key step in these syntheses involved the reaction of a phosphite with hexachlorocyclopentadiene. Attempts were made to effect intra-molecular Diels-Alder cyclization of these compounds without rearrangement in an effort to synthesize longifolene. Thermal cyclization occurred in one case, that of 4b, in low yield, but rearrangement preceded cyclization. The molecular structure of this cyclization product was unequivocally elucidated as 5a by X-ray crystallographic analysis. Consideration of this structure, which requires reduction as well as rearrangement, suggested a more efficient synthesis. Reduction of (E)-4b with lithium aluminum hydride followed by thermal cyclization gave 5a in good yield. Benzyl ether 5b was similarly prepared. Both 5a and 5b are potential intermediates in a synthesis of isolongifolene. © 1978 American Chemical Society.
• Glass, R. S., Duchek, J. R., Klug, J. T., & Wilson, G. S. (1977). Facilitation of dialkyl sulfide oxidation by neighboring groups [1]. Journal of the American Chemical Society, 99(22), 7349-7350.
• Glass, R. S., & Duchek, J. R. (1976). The structure of dehydromethionine. An azasulfonium salt. Journal of the American Chemical Society, 98(4), 965-969.
  More info

  PMID: 1245707;Abstract: The crystal and molecular structure of dehydromethionine has been determined by x-ray crystallographic techniques. The compound crystallizes in the monoclinic space group P21/n with a = 5.658 (6) Å, b = 8.844 (6) Å, c = 13.605 (9) Å, α = 90°, β = 92.54 (2)°, γ = 90°, and Z = 4. The atoms other than hydrogen were located using direct methods, and the hydrogen atoms were located by Fourier difference maps. Full-matrix least-squares refinement led to a conventional R factor of 0.044. Key features of the molecular structure are an envelope conformation of the five-membered isothiazolidine ring and trivalent sulfur bonded to pyramidal nitrogen. The geometry about the nitrogen atom suggests the absence of p-d π bonding between the sulfur and nitrogen atoms in the azasulfonium linkage. It is suggested that the geometry and bonding in azasulfonium salts is analogous to that in the isoelectronic sulfonium ylides.
• Glass, R. S., & Hoy, R. C. (1976). Conversion of aromatic aldehydes into nitriles via N-tosylimines. Tetrahedron Letters, 17(21), 1781-1782.
• Glass, R. S., & Hoy, R. C. (1976). Novel reactions of cyanide anion with sulfonimides. Tetrahedron Letters, 17(21), 1777-1780.
• Goldberg, I. B., Crowe, H. R., Wilson, G. S., & Glass, R. S. (1976). 2,3,7,8-Tetramethoxythianthrene. A novel ground state triplet dication, the neutral photogenerated triplet, and the radical cation. Journal of Physical Chemistry, 80(9), 988-992.
  More info

  Abstract: The dication of 2,3,7,8-tetramethoxythianthrene was studied in solid nitromethane at 77 K by computer-controlled electron spin resonance. The Δm = 2 transition was observed, yielding a value of D* = 0.106 cm-1. For comparison the values of D* for thianthrene and 2,3,7,8-tetramethoxythianthrene photogenerated triplets determined were 0.135 and 0.121 cm-1, respectively. Lifetimes of these triplet states were also determined. Frozen solutions of the tetramethoxythianthrene dication exhibited a very broad Δm = 1 signal that could not be resolved into components D and E of the dipolar tensor. The free energy separation between the triplet and singlet states is between 90 and 190 cm-1. The ESR spectrum of the cation was redetermined. The hyperfine splittings at 23°C in nitromethane were aS = 7.30 ± 0.05 G, aH(OCH3) = 0.28 ± 0.02 G, and aH(1,4,6,9) = 0.87 ± 0.04 G, and the g factor is 2.00732 ± 0.00006.
• Glass, R. S., & Smith, D. L. (1974). Remarkable enhancement of dienophilicity by the trifluoromethanesulfonyl group. Phenyl(trifluoromethanesulfonyl)acetylene. Journal of Organic Chemistry, 39(25), 3712-3715.
  More info

  Abstract: Phenyl(trifluoromethanesulfonyl)acetylene, prepared from the lithium salt of phenylacetylene and trifluoromethanesulfonic acid anhydride, undergoes exceptionally facile Diels-Alder reactions with tetraphenylcyclopentadienone, 1,3-diphenylisobenzofuran, cyclopentadiene, and 1,3-cyclohexadiene. The rates of these reactions and those of the corresponding reactions with other C6H5C≡CX derivatives were measured and compared. The rate of reaction of phenyl(trifluoromethanesulfonyl)acetylene with cyclopentadiene in ethyl acetate at room temperature was found to be 1.7 times as fast as the rate of reaction of dimethyl acetylenedicarboxylate with this diene. The reasons for the remarkable dienophilicity of phenyl(trifluoromethanesulfonyl)acetylene are discussed.
• Glass, R. S., Williams Jr., E. B., & Wilson, G. S. (1974). Formation of high-energy phosphate bonds effected by electron-deficient sulfides. Biochemistry, 13(14), 2800-2805.
  More info

  PMID: 4367173;Abstract: Electron-deficient sulfides are postulated as intermediates in the formation of a phosphorylated sulfonium salt which has previously been suggested as the high energy phosphorylating intermediate of respiratory chain-linked oxidative phosphorylation. To test the ability of electron-deficient sulfides to effect phosphorylation of adenine nun the presence of orthophosphate, an aromatic sulfur cation radical and dication are used as models. Treatment of the tetra-n-butylammonium salts of adenosine 5′-monophosphate and orthophosphoric acid in anhydrous acetonitrile with thianthrene perchlorate in the molar ratio of 1:1:2 results in the rapid formation of adenosine 5′-diphosphate and triphosphate in a combined yield of 16% based on the amount of thianthrene perchlorate added or 52% yield, based on the amount of adenosine 5′-monophosphate consumed. The thianthrene perchlorate is converted to thianthrene and thianthrene sulfoxide. Similar reactions with 2,3,7,8-tetramethoxythianthrene diperchlorate in place of thianthrene perchlorate result in the rapid formation of adenosine 5′-diphosphate and triphosphate in a combined yield of 19% based on dication added or 73% yield based on adenosine 5′-monophosphate consumed. Evidence concerning the mechanisms of these reactions is presented and discussed as well as their biological significance. In particular, theoretical consideration of electron-deficient aliphatic sulfides as intermediates in oxidative phosphorylation is presented. A key suggestion is that the oxidation potential of aliphatic sulfides and the stability of aliphatic sulfur cation radicals and/or dications can be affected by neighboring group participation.
• Glass, R. S. (1973). A facile synthesis of trimethylsilyl thioethers. Journal of Organometallic Chemistry, 61(C), 83-90.
  More info

  Abstract: Imidazole catalyzes the reaction of thiols with hexamethyldisilazane. This procedure affords a convenient method for the synthesis of trimethylsilyl thioethers. Some aspects of the mechanism of this reaction are discussed. © 1973.
• Glass, R. S., Britt, W. J., Miller, W. N., & Wilson, G. S. (1973). 2,3,7,8-Tetramethoxythianthrene dication. An isolable thianthrene dication [12]. Journal of the American Chemical Society, 95(7), 2375-2376.
• Glass, R. S., Kwoh, S., & Oliveto, E. P. (1973). Ketone exchange in a sugar bisacetal. Carbohydrate Research, 26(1), 181-189.
  More info

  Abstract: An acid-catalyzed reaction of 2,3:4,6-di-O-isopropylidene-α-l-sorbofuranose with ketones resulted in replacement of the isopropylidene groups with alkylidene groups derived from the ketonic solvent. Kinetically controlled exchange occurs at the 4,6-position. Under equilibrium conditions exchange occurs at the 2,3- as well as the 4,6-position. Participation by the hydroxyl group at C-1 in the rate determining step of exchange at the 2,3-position could not be demonstrated. © 1973.
• Westley, J. W., Oliveto, E. P., Berger, J., Evans Jr., R. H., Glass, R., Stempel, A., Toome, V., & Williams, T. (1973). Chemical transformations of antibiotic x-537A and their effect on antibacterial activity. Journal of Medicinal Chemistry, 16(4), 397-403.
  More info

  PMID: 4716184;Abstract: A number of derivatives of the polyether antibiotic X-537A have been tested in vitro vs. Bacillus E and Bacillus TA and the results clearly indicate that all the oxygen functions involved in ligand formation with cations and intramolecular hydrogen bonding (as revealed by X-ray analysis) contribute to the biological activity of the antibiotic. In addition, a number of derivatives at the C-5 position of the aromatic chromophore exhibited a qualitative correlation between their partition coefficients (octanol-water) and in vitro activity.
• Glass, R. S., & Williams, T. (1972). An unexpected conformational preference in a sugar derivative. Journal of Organic Chemistry, 37(21), 3366-3368.
  More info

  PMID: 5072904;
• Glass, R. S. (1971). Nucleophilic displacement at carbon bearing nitrogen. Journal of the Chemical Society D: Chemical Communications, 1546-1547.
  More info

  Abstract: Carbon-carbon bonds are formed at the expense of carbon-nitrogen bonds by nucleophilic displacement on trifluoromethanesulphonimides.
• Corey, E. J., & Glass, R. S. (1967). Studies on the molecular geometry of the norbornyl cation. I. The synthesis and acetolysis of the exo- and endo-4,5-exo-trimethylene-2-norbornyl p-toluenesulfonates. Journal of the American Chemical Society, 89(11), 2600-2610.
  More info

  Abstract: 4,5-exo-Trimethylene-2-norbornene (10) has been synthesized from a monosubstituted cyclopentadiene 9 using an intramolecular Diels-Alder reaction, and from this intermediate exo- and endo-4,5-exo-trimethylene-2-norbornyl p-toluenesulfonates (11, R = Ts, and 16, R = Ts) have been prepared. These sulfonates undergo acetolysis (25°) at relative rates of 8.6:1. The ratio of rate constants (25°) for acetolysis of the exo-sulfonate 11, R = Ts, and 2-exo-norbornyl p-toluenesulfonate is 1:85, whereas the corresponding ratio for the endo-sulfonate 16, R = Ts, and 2-endo-norbornyl p-toluenesulfonate is 1:2.5. The depressed rate for the tricyclic exo-sulfonate 11, R = Ts, relative to 2-exo-norbornyl p-toluenesulfonate is readily explained in terms of bridging of carbon in the transition state for ionization, but seems to be contrary to expectations based on ionization to a localized (classical) carbonium ion. Thus, the present results favor the bridged-ion mechanism for acetolysis of 2-exo-norbornyl arene-sulfonates.

Presentations

• Glass, R. S. (2016, July). Professor of Chemistry. German Chemical Society. Tuebingen, Germany.
• Glass, R. S. (2016, March). Professor of Chemistry. Ernest Guenther Award Symposium. San Diego, CA: ACS.