Dominic V McGrath

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Chapters

• Gemma D. D'Ambruoso, ., & Dominic V. McGrath, . (2005). ENERGY HARVESTING IN SYNTHETIC DENDRITIC MATERIALS. In Energy Harvesting Materials(pp 281-334). WORLD SCIENTIFIC.

Journals/Publications

• Smeu, M., Shepard, S., Saraiva-souza, A., Parida, K. N., Monti, O. L., Mcgrath, D. V., Ivie, J. A., Himmelhuber, R., Dyer, D., Bamberger, N. D., Monti, O. L., Smeu, M., Shepard, S., Saraiva-souza, A., Parida, K. N., Monti, O. L., Mcgrath, D. V., Ivie, J. A., Himmelhuber, R., , Dyer, D., et al. (2021). Correlated Energy-Level Alignment Effects Determine Substituent-Tuned Single-Molecule Conductance.. ACS applied materials & interfaces, 13(3), 4267-4277. doi:10.1021/acsami.0c19404
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  The rational design of single-molecule electrical components requires a deep and predictive understanding of structure-function relationships. Here, we explore the relationship between chemical substituents and the conductance of metal-single-molecule-metal junctions, using functionalized oligophenylenevinylenes as a model system. Using a combination of mechanically controlled break-junction experiments and various levels of theory including non-equilibrium Green's functions, we demonstrate that the connection between gas-phase molecular electronic structure and in-junction molecular conductance is complicated by the involvement of multiple mutually correlated and opposing effects that contribute to energy-level alignment in the junction. We propose that these opposing correlations represent powerful new "design principles" because their physical origins make them broadly applicable, and they are capable of predicting the direction and relative magnitude of observed conductance trends. In particular, we show that they are consistent with the observed conductance variability not just within our own experimental results but also within disparate molecular series reported in the literature and, crucially, with the trend in variability across these molecular series, which previous simple models fail to explain. The design principles introduced here can therefore aid in both screening and suggesting novel design strategies for maximizing conductance tunability in single-molecule systems.
• Xu, Z., Xu, W., Xu, H., Rezaee, E., Ramachandran, R., Mcgrath, D. V., Hu, Q., El-assaad, T. H., Chen, Q., Xu, Z., Xu, W., Xu, H., Rezaee, E., Ramachandran, R., Mcgrath, D. V., Hu, Q., El-assaad, T. H., & Chen, Q. (2021). Dual Defect-Passivation Using Phthalocyanine for Enhanced Efficiency and Stability of Perovskite Solar Cells.. Small (Weinheim an der Bergstrasse, Germany), 17(1), e2005216. doi:10.1002/smll.202005216
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  Semiconducting molecules have been employed to passivate traps extant in the perovskite film for enhancement of perovskite solar cells (PSCs) efficiency and stability. A molecular design strategy to passivate the defects both on the surface and interior of the CH3 NH3 PbI3 perovskite layer, using two phthalocyanine (Pc) molecules (NP-SC6 -ZnPc and NP-SC6 -TiOPc) is demonstrated. The presence of lone electron pairs on S, N, and O atoms of the Pc molecular structures provides the opportunity for Lewis acid-base interactions with under-coordinated Pb2+ sites, leading to efficient defect passivation of the perovskite layer. The tendency of both NP-SC6 -ZnPc and NP-SC6 -TiOPc to relax on the PbI2 terminated surface of the perovskite layer is also studied using density functional theory (DFT) calculations. The morphology of the perovskite layer is improved due to employing the Pc passivation strategy, resulting in high-quality thin films with a dense and compact structure and lower surface roughness. Using NP-SC6 -ZnPc and NP-SC6 -TiOPc as passivating agents, it is observed considerably enhanced power conversion efficiencies (PCEs), from 17.67% for the PSCs based on the pristine perovskite film to 19.39% for NP-SC6 -TiOPc passivated devices. Moreover, PSCs fabricated based on the Pc passivation method present a remarkable stability under conditions of high moisture and temperature levels.
• Parida, K. N., Mcgrath, D. V., El-assaad, T. H., Cesario, M. F., Parida, K. N., Mcgrath, D. V., El-assaad, T. H., & Cesario, M. F. (2020). Sterically driven metal-free oxidation of 2,7-di-tert-butylpyrene. Green Chemistry, 22(18), 5966-5971. doi:10.1039/d0gc02000a
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  We disclose an unprecedented single-step metal-free green oxidation of 2,7-di-tert-butylpyrene selectively into either the corresponding 4,5-dione or 4,5,9,10-tetraone, two key building blocks used for organic optoelectronic applications using hypervalent iodine oxyacids. This new method results in dramatic improvements in terms of yield, selectivity (dione vs. tetraone), ease of workup, cost and toxicity.
• Parida, K. N., Monti, O. L., Mcgrath, D. V., Ivie, J. A., Bamberger, N. D., Monti, O. L., Parida, K. N., Monti, O. L., Mcgrath, D. V., Ivie, J. A., & Bamberger, N. D. (2020). Unsupervised Segmentation-Based Machine Learning as an Advanced Analysis Tool for Single Molecule Break Junction Data. Journal of Physical Chemistry C, 124(33), 18302-18315. doi:10.1021/acs.jpcc.0c03612
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  Improved understanding of charge-transport in single molecules is essential for harnessing the potential of molecules, e.g., as circuit components at the ultimate size limit. However, interpretatio...
• Parida, K. N., Monti, O. L., Parida, K. N., Monti, O. L., Monti, O. L., Mcgrath, D. V., Ivie, J. A., Mcgrath, D. V., Ivie, J. A., Bamberger, N. D., & Bamberger, N. D. (2020). Correction to “Unsupervised Segmentation-Based Machine Learning as an Advanced Analysis Tool for Single Molecule Break Junction Data”. Journal of Physical Chemistry C, 124(43), 24029-24031. doi:10.1021/acs.jpcc.0c08721
• Saavedra, S. S., Oquendo, L. E., Mcgrath, D. V., Ehamparam, R., & Armstrong, N. R. (2019). Zinc Phthalocyanine–Phosphonic Acid Monolayers on ITO: Influence of Molecular Orientation, Aggregation, and Tunneling Distance on Charge-Transfer Kinetics. Journal of Physical Chemistry C, 123(12), 6970-6980. doi:10.1021/acs.jpcc.8b10301
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  Efficient charge harvesting at electrodes is critical for the effective performance of organic photovoltaics and is strongly influenced by the first molecular monolayer at the transparent conducting oxide electrode. Herein, we present a study of the relationship between molecular orientation and tunneling distance on charge-transfer rates between a tethered sub-monolayer/monolayer of phosphonic acid (PA)-functionalized Zn phthalocyanines (ZnPcs) and an indium tin oxide (ITO) surface by a combination of electrochemical techniques and waveguide tools such as attenuated total reflectance (ATR) UV–vis spectroscopy and potential-modulated ATR (PM-ATR) spectroelectrochemistry. The distance between the main chromophore and PA anchoring group was modulated by an aliphatic carbon of various lengths (n = 3, 9, 10, or 11) that resulted in an extended distance of 7–18 A between the ZnPcs and the ITO surface. Modified ITO surfaces were composed of monomeric and aggregated subpopulations of ZnPcs with molecular orienta...
• Xu, Z., Rezaee, E., Mcgrath, D. V., Mayukh, M., Li, M., Hu, Q., Chen, Q., & Cao, Y. (2019). Molecular Design Strategy in Developing Titanyl Phthalocyanines as Dopant-Free Hole-Transporting Materials for Perovskite Solar Cells: Peripheral or Nonperipheral Substituents?. ACS applied materials & interfaces, 11(40), 36535-36543. doi:10.1021/acsami.9b09490
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  We demonstrate a molecular design strategy to enhance the efficiency of phthalocyanine (Pc)-based hole-transporting materials (HTMs) in perovskite solar cells (PSCs). Herein, two titanyl phthalocyanine (TiOPc) derivatives are designed and applied as dopant-free HTMs in planar n-i-p-structured PSCs. The newly developed TiOPc compounds possess eight n-hexylthio groups attached to either peripheral (P-SC6-TiOPc) or nonperipheral (NP-SC6-TiOPc) positions of the Pc ring. Utilizing these dopant-free HTMs in PSCs with a mixed cation perovskite as the light-absorbing material and tin oxide (SnO2) as the electron-transporting material (ETM) results in a considerably enhanced efficiency for NP-SC6-TiOPc-based devices compared to PSCs using P-SC6-TiOPc. Hence, all of the photovoltaic parameters, including power conversion efficiency (PCE), fill factor, open-circuit voltage, and short-circuit current density, are remarkably improved from 5.33 ± 1.01%, 33.34 ± 3.45%, 0.92 ± 0.18 V, and 17.33 ± 2.08 mA cm-2 to 15.83 ± 0.44%, 69.03 ± 1.59%, 1.05 ± 0.01 V, and 21.80 ± 0.36 mA cm-2, respectively, when using the nonperipheral-substituted TiOPc derivative as the HTM in a PSC. Experimental and computational analysis suggests more compact molecular packing for NP-SC6-TiOPc than P-SC6-TiOPc in the solid state due to stronger π-π interactions, leading to thin films with better quality and higher performance in hole extraction and transportation. PSCs with NP-SC6-TiOPc also offer much higher long-term stability than P-SC6-TiOPc-based devices under ambient conditions with a relative humidity of 75%.
• Ehamparam, R., Oquendo, L. E., Liao, M. W., Brynnel, A. K., Ou, K., Armstrong, N. R., Mcgrath, D. V., & Saavedra, S. S. (2017). Axially Bound Ruthenium Phthalocyanine Monolayers on Indium Tin Oxide: Structure, Energetics, and Charge Transfer Properties. ACS Applied Materials & Interfaces, 9(34), 29213-29223. doi:http://doi.org/10.1021/acsami.7b07394
• Doetschman, T., Utzinger, U., McGrath, D. V., Geest, J. P., McIntyre, J. O., Ardila, D. C., Smith, T., Howerton, S. J., Maestas, D. R., & Haskett, D. (2016). 2-Photon Characterization of Optical Proteolytic Beacons for Imaging Changes in Matrix-Metalloprotease Activity in a Mouse Model of Aneurysm. Microscopy and Microanalysis. doi:10.1017/s1431927616000088
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  Abstract Abdominal aortic aneurysm is a multifactorial disease that is a leading cause of death in developed countries. Matrix-metalloproteases (MMPs) are part of the disease process, however, assessing their role in disease initiation and progression has been difficult and animal models have become essential. Combining Förster resonance energy transfer (FRET) proteolytic beacons activated in the presence of MMPs with 2-photon microscopy allows for a novel method of evaluating MMP activity within the extracellular matrix (ECM). Single and 2-photon spectra for proteolytic beacons were determined in vitro . Ex vivo experiments using the apolipoprotein E knockout angiotensin II-infused mouse model of aneurysm imaged ECM architecture simultaneously with the MMP-activated FRET beacons. 2-photon spectra of the two-color proteolytic beacons showed peaks for the individual fluorophores that enable imaging of MMP activity through proteolytic cleavage. Ex vivo imaging of the beacons within the ECM revealed both microstructure and MMP activity. 2-photon imaging of the beacons in aneurysmal tissue showed an increase in proteolytic cleavage within the ECM ( p
• Haskett, D. G., Maestas, D., Howerton, S., Smith, T., Ardilia, C., Doetschman, T. C., Utzinger, U., Mcgrath, D. V., McIntyre, J. O., & Vande Geest, J. P. (2016). 2-Photon characterization of optical proteolytic beacons for imaging changes in MMP activity in a mouse model of aneurysm. Microscopy and Microanalysis, 22, 349-360. doi:http://dx.doi.org/10.1017/S1431927616000088
• Lin, H., MacDonald, G. A., Shi, Y., Polaske, N. W., McGrath, D. V., Marder, S. R., Armstrong, N. R., Ratcliff, E. L., & Saavedra, S. S. (2015). Influence of Molecular Orientation on Charge Transfer Processes at Phthalocyanine/Metal Oxide Interfaces and Relationship to Organic Photovoltaic Performance. Journal of Physical Chemistry C, 119(19), 10304-10313. doi:http://dx.doi.org/10.1021/acs.jpcc.5b02971
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  The effect of the molecular orientation distribution of the first monolayer of donor molecules at the hole-harvesting contact in an organic photovoltaic (OPV) on device efficiency was investigated. Two zinc phthalocyanine (ZnPc) phosphonic acids (PA) deposited on indium tin oxide (ITO) electrodes are compared: ZnPc(PA)4 contains PA linkers in all four quadrants, and ZnPcPA contains a PA linker in one quadrant. ZnPcPA monolayers exhibited a broad distribution of molecular orientations whereas ZnPc(PA)4 adsorption produced a monolayer with a narrower orientation distribution with the molecular plane more parallel to the ITO surface. We used potential-modulated attenuated total reflectance spectroelectrochemistry (PM-ATR) to characterize the charge-transfer kinetics of these films and show that the highest rate constants correspond to ZnPc subpopulations that are oriented more parallel to the ITO surface plane. For ZnPc(PA)4, rate constants exceeded 104 s–1 and are among the highest ever reported for a surface-confined redox couple, which is attributable to both its orientation and the small ZnPc–electrode separation distance. The performance of OPVs with ITO hole-harvesting contacts modified with ZnPc(PA)4 was comparable to that achieved with highly activated bare ITO contacts, whereas for ZnPcPA-modified contacts, the OPV performance was similar to that observed with (hole-blocking) alkyl-PA modifiers. These results demonstrate the synergism between molecular structure, energetics, and dynamics at interfaces in OPVs.
• Mayukh, M., Macech, M. R., Placencia, D., Cao, Y., Armstrong, N. R., & McGrath, D. V. (2015). Solution Processed Titanyl Phthalocyanines as Donors in Solar Cells: Photoresponse to 1000 nm. ACS Applied Materials and Interfaces, 7(43), 23912-23919. doi:http://dx.doi.org/10.1021/acsami.5b05900
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  We report a route to thin-film polymorphs of soluble TiOPc derivatives that exhibit similar near-IR absorptivities as vapor deposited thin-films of the parent TiOPc chromophore (phase-I and phase-II polymorphs) and demonstrate that solution-processed planar and bulk heterojunction solar cells fabricated with one of these derivatives exhibited photoactivity throughout the same near-IR wavelength range without compromising VOC. Solution-processed thin-films of soluble octakis(alkylthio)-substituted TiOPc derivatives 1–3 exhibit absorption extending to 1000 nm. When incorporated into OPV devices, the contributions from the lowest CT excitonic state (QB band) of 1 to device performance were evident in both PHJ and BHJ architectures, indicating sufficient driving force for PIET. This contribution was improved via intimate mixing of donor and acceptor molecules in a BHJ architecture, albeit with a decrease in efficiency. IPCE of the best performing BHJ device revealed a contribution from 1 exceeding that of acceptor PCBM, and extending to 1000 nm.
• Muli, D. K., Rajaputra, P., You, Y., & McGrath, D. V. (2015). Asymmetric ZnPc-TEG photosensitizers: the effect of Pc substitution on phototoxicity. Tetrahedron Letters, 56(45), 6236-6239. doi:http://dx.doi.org/10.1016/j.tetlet.2015.09.101
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  Asymmetric zinc phthalocyanine (ZnPc) isomers with triethylene glycol (TEG) moieties in the peripheral (1a) and non-peripheral (1b) substitution were designed, synthesized, characterized, and their phototoxicity on colon-26 cells evaluated. TEG moieties as water solubilizing groups were incorporated at peripheral or non-peripheral positions to investigate the effect of their position on the Pc on the photodynamic activity. UV/vis analyses indicated a small red-shifting of the Q band of the non-peripheral ZnPc–TEG 1b (ca. 4 nm) relative to 1a in dichloromethane and THF. n-Octanol/pH 7.4 buffer partition coefficients revealed that 1b was marginally more hydrophilic than 1a with log D7.4 values of 2.44 and 2.46, respectively. Fluorescence emission aggregation studies indicate that 1b is ca. 61% (DMSO) and 32% (phosphate buffer) less aggregated than the peripherally substituted ZnPc 1a suggesting that non-peripheral substitution decreased overall aggregation of the photosensitizers. Singlet oxygen generation studies are reported. Both ZnPc–TEGs showed negligible dark toxicity on colon 26 cells with 10 μM 1a and 1b. Irradiation (690 nm, 45 J/cm2) of the cells produced an IC50 value >25 μM for 1a and an IC50 value between 1 and 5 μM for 1b. Overall, the non-peripheral isomer 1b was found to be more photodynamically active.
• Chen, X., Lu, C., Huang, Y., & McGrath, D. V. (2015). Modification of alkyne-functionalized asymmetric phthalocyanines by CuI-catalyzed azide-alkyne cycloaddition. Tetrahedron, 71(48), 9154-9160. doi:http://dx.doi.org/10.1016/j.tet.2015.09.074
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  The use of asymmetric phthalocyanines (Pcs) as platforms for the preparation of several asymmetric hexatriazolyl-monohydroxyphthalocyanines via copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction was investigated. Asymmetric Pcs 5a and 5b were prepared through statistical macrocyclization of phthalonitriles (Pns) 1a and 2 to give PMB-protected 4a and 4b, which afforded asymmetric Pcs 5a and 5b after acidic cleavage. The ‘ROMP-Capture-Release’ method as a synthetic approach to prepare asymmetric Pc 5b was also evaluated. TIPS-protection of the terminal alkynes was necessary to prevent cross-coupling during the ring-opening metathesis polymerization (ROMP) step. Zinc Pc 5b was successfully used as a scaffold for functional modification under CuAAC conditions using several azides bearing hydrophobic, photo-crosslinkable, or electroactive moieties. Monitoring the CuAAC reaction by both UV/Vis and FTIR spectroscopies provided insight into the role of azide equivalent, reaction time, and catalyst on reaction progress.
• Lin, H., Polaske, N. W., Oquendo, L. E., Gliboff, M., Knesting, K. M., Nordlund, D., Ginger, D. S., Ratcliff, E. L., Beam, B. M., Ratcliff, E. L., Armstrong, N. R., McGrath, D. V., & Saavedra, S. S. (2012). Electron Transfer Processes in Zinc Phthalocyanine-Phosphonic Acid Monolayers on ITO: Characterization of Orientation and Charge Transfer Kinetics By Waveguide Spectroelectrochemistry. J. Phys. Chem. Lett, 3, 1154-1158. doi:http://dx.doi.org/10.1021/jz3002426
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  Using a monolayer of zinc phthalocyanine (ZnPcPA) tethered to indium tin oxide (ITO) as a model for the donor/transparent conducting oxide (TCO) interface in organic photovoltaics (OPVs), we demonstrate the relationship between molecular orientation and charge-transfer rates using spectroscopic, electrochemical, and spectroelectrochemical methods. Both monomeric and aggregated forms of the phthalocyanine (Pc) are observed in ZnPcPA monolayers. Potential-modulated attenuated total reflectance (PM-ATR) measurements show that the monomeric subpopulation undergoes oxidation/reduction with ks,app = 2 × 102 s–1, independent of Pc orientation. For the aggregated ZnPcPA, faster orientation-dependent charge-transfer rates are observed. For in-plane-oriented Pc aggregates, ks,app = 2 × 103 s–1, whereas for upright Pc aggregates, ks,app = 7 × 102 s–1. The rates for the aggregates are comparable to those required for redox-active interlayer films at the hole-collection contact in organic solar cells.
• Muli, D. K., Carpenter, B. L., Mayukh, M., Ghiladi, R. A., & Mcgrath, D. V. (2015). Dendritic near-IR absorbing zinc phthalocyanines for antimicrobial photodynamic therapy. Tetrahedron Letters, 56(23), 3541-3545. doi:http://dx.doi.org/10.1016/j.tetlet.2015.01.076
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  Design, synthesis, characterization, and photodynamic activity of dendritic, water-soluble zinc phthalocyanine (ZnPc) isomers 1a and 1b are described. Bearing terminal triethylene glycol (TEG) moieties as water solubilizing groups that were attached to the Pc core using Cu(I) catalyzed alkyne–azide cycloaddition (CuAAC), 1a and 1b are readily soluble in H2O, polar aprotic, and protic organic solvents. UV/Vis analyses indicate that the Q band of the non-peripheral ZnPc 1b is ca. 80 nm red-shifted relative to the peripheral one with absorption at 805 nm (distilled water). 1a and 1b have log D7.4 values of 0.22 and 0.05, respectively, suggesting that the non-peripheral substitution improved the overall hydrophilicity. Aggregation studies indicate that non-peripherally substituted 1b is significantly less aggregated in aqueous media than peripherally substituted 1a. Singlet oxygen generation studies are reported. Both ZnPcs showed negligible dark toxicity on bacteria and yeast with 10 μM 1a and 1b. Illumination (400–850 nm) of Pseudomonas aeruginosa with 10 μM of 1a produced a 90% cell inactivation while Acinetobacter baumannii with 10 μM 1b showed detection limit (99.9999+%) cell inactivation, demonstrating the antimicrobial photoactivity of these dyes.
• Muli, D. K., Rajaputra, P., You, Y., & McGrath, D. V. (2014). Asymmetric ZnPc–rhodamine B conjugates for mitochondrial targeted photodynamic therapy. Bioorganic & Medicinal Chemistry Letters, 24(18), 4496-4500. doi:http://dx.doi.org/10.1016/j.bmcl.2014.07.082
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  Design, synthesis, characterization, and photodynamic activity of mitochondria specific asymmetric ZnPc–Rh B conjugates are described. Conjugation of asymmetric ZnPc–OH chromophores 3a and 3b with rhodamine B via the corresponding DIC-activated ester gave the desired near IR-absorbing asymmetric ZnPc–Rh B conjugates 1a and 1b. Conjugates 1a and 1b were shown to produce singlet oxygen upon illumination in DMSO, MeOH and THF. Fluorescence aggregation studies of the dyes 1a, 1b, 3a and 3b in DMSO and phosphate buffered saline (PBS) solution showed that conjugates 1a and 1b were less aggregated compared to the corresponding non-conjugates 3a and 3b suggesting that incorporation of Rh B lowered aggregation of the conjugates in the PBS solution. The four dyes studied have log D7.4 values between 2.31 and 2.48, with the sulfur-containing conjugate 1b being the most hydrophobic. All the dyes showed negligible dark toxicity when colon 26 cells were treated with 5 μM of the dyes while 10–15% cell death was observed for dye concentrations of 15 μM. Illumination (700 ± 40 nm, 45 J/cm2, 15 min) of the cells ([dye] = 15 μM) gave 70% cell death for ZnPc–Rh B conjugates 1a and 1b while no killing for non-conjugates 3a and 3b suggesting that the incorporation of the Rh B in the photosensitizer lowered the aggregation and subsequently improved cellular uptake and phototoxicity.
• Rao, V., Navath, S., Kottur, M., McElhanon, J. R., & McGrath, D. V. (2013). An efficient reverse Diels-Alder approach for the synthesis of N-alkyl bismaleimides. Tetrahedron Letters, 54(37), 5011-5013. doi:http://dx.doi.org/10.1016/j.tetlet.2013.07.002
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  Abstract: Bismaleimides are useful precursors for Diels-Alder reactions, Michael additions, and thiol-maleimide based conjugation for the synthesis of materials and polymers. Use of bismaleimide cross linkers for generating polymers, bioconjugate molecules, and useful imaging molecules is an active area of research. An efficient and practical synthetic protocol for N-alkyl bis-maleimide cross linkers starting from furan protected maleimide employing a reverse Diels-Alder reaction is reported. © 2013 Elsevier Ltd. All rights reserved.
• Warren, P. D., Sycks, D. G., Mcgrath, D. V., & Vande Geest, J. P. (2013). Modeling the microstructurally dependent mechanical properties of poly(ester-urethane-urea)s. Journal of Biomedical Materials Research. Part A, 101(12), 3382-7. doi:http://dx.doi.org/10.1002/jbm.a.34641
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  Poly(ester-urethane-urea) (PEUU) is one of many synthetic biodegradable elastomers under scrutiny for biomedical and soft tissue applications. The goal of this study was to investigate the effect of the experimental parameters on mechanical properties of PEUUs following exposure to different degrading environments, similar to that of the human body, using linear regression, producing one predictive model. The model utilizes two independent variables of poly(caprolactone) (PCL) type and copolymer crystallinity to predict the dependent variable of maximum tangential modulus (MTM). Results indicate that comparisons between PCLs at different degradation states are statistically different (p < 0.0003), while the difference between experimental and predicted average MTM is statistically negligible (p < 0.02). The linear correlation between experimental and predicted MTM values is R(2) = 0.75.
• Banister, M., Clark, R., Coiner, E., Geronov, Y., McWilliams, M., Sias, R., Walters, G., & McGrath, D. (2012). Study of a smart polymer medical device, product development obstacles and innovative solutions. Proc. SPIE 8343, Industrial and Commercial Applications of Smart Structures Technologies, 8343(30 March 2012), 83430I. doi:http://doi.org/10.1117/12.915529
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  Abstract: The concept is simple, within the pump a pH responsive polymer actuator swells in volume under electrically controlled stimulus. As the actuator swells it presses against a drug reservoir, as the reservoir collapses the drug is metered out to the patient. From concept to finished product, engineering this smart system entailed integration across multiple fields of science and engineering. Materials science, nanotechnology, polymer chemistry, organic chemistry, electrochemistry, molecular engineering, electrical engineering, and mechanical engineering all played a part in solutions to multiple technical hurdles. Some of these hurdles where overcome by tried and true materials and component engineering, others where resolved by some very creative out of the box thinking and tinkering. This paper, hopefully, will serve to encourage others to venture into unfamiliar territory as we did, in order to overcome technical obstacles and successfully develop a low cost smart medical device that can truly change a patient's life. © 2012 SPIE.
• Kevwitch, R. M., Shanahan, C. S., & McGrath, D. V. (2012). Vanillin and o-vanillin oligomers as models for dendrimer disassembly. New Journal of Chemistry, 36(2), 492-505. doi:http://doi.org/10.1039/c1nj20841a
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  Abstract: Linear analogs have been synthesized to model disassembling dendrimers. These linear analogs provide a facile synthesis to molecules that can be used to test new trigger groups and cleavage vectors. Vanillin and o-vanillin were used as the monomer units of these analogs and two trigger groups, allyl and o-nitrobenzyl, were chosen to test the disassembly process. Allyl triggered analogs 1a-d and 3a-d and o-nitrobenzyl triggered analogs 2a-c and 4a-c showed good to excellent disassembly as followed by the evolution of p-nitrophenoxide reporter ion by UV-Visible spectroscopy. The rate and yield of disassembly was shown to depend on experimental conditions as well as length of the cleavage vector. © 2012 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
• Schweitzer, G., Rao, P., Mcgrath, D. V., Gurr, A., Geronov, Y. M., Eichorst, R., & Banister, M. (2012). Molecular engineering of polymer actuators for biomedical and industrial use. Proceedings of SPIE, 8340. doi:10.1117/12.917495
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  Five key materials engineering components and how each component impacted the working performance of a polymer actuator material are investigated. In our research we investigated the change of actuation performance that occurred with each change we made to the material. We investigated polymer crosslink density, polymer chain length, polymer gelation, type and density of reactive units, as well as the addition of binders to the polymer matrix. All five play a significant role and need to be addressed at the molecular level to optimize a polymer gel for use as a practical actuator material for biomedical and industrial use.
• Mayukh, M., Lu, C., Hernandez, E., & McGrath, D. V. (2011). Peripheral substitution of a near-IR-absorbing soluble phthalocyanine using "click" chemistry. Chemistry - A European Journal, 17(30), 8472-8478. doi:http://doi.org/10.1002/chem.201001427
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  PMID: 21671288;Abstract: A series of near-IR-absorbing soluble phthalocyanines (Pcs) with eight alkyne moieties as side chains of the chromophore have been synthesized. One of these Pcs has been used as a scaffold for functional group modification using alkyne-azide click chemistry with various azides. This led to a small library of Pcs with photo and thermal crosslinkable, dendritic, and hydrophilic moieties starting from a single Pc molecule. A patterned thin film was fabricated by photocrosslinking one of these Pc derivatives. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
• Polaske, N. W., Lin, H., Tang, A., Mayukh, M., Oquendo, L. E., Green, J. T., Ratcliff, E. L., Armstrong, N. R., Saavedra, S. S., & McGrath, D. V. (2011). Phosphonic acid functionalized asymmetric phthalocyanines: synthesis, modification of indium tin oxide, and charge transfer. Langmuir, 27(24). doi:http://dx.doi.org/10.1021/la203126c
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  Metalated and free-base A(3)B-type asymmetric phthalocyanines (Pcs) bearing, in the asymmetric quadrant, a flexible alkyl linker of varying chain lengths terminating in a phosphonic acid (PA) group have been synthesized. Two parallel series of asymmetric Pc derivatives bearing aryloxy and arylthio substituents are reported, and their synthesis and characterization through NMR, combustion analysis, and MALDI-MS are described. We also demonstrate the modification of indium tin oxide (ITO) substrates using the PA functionalized asymmetric Pc derivatives and monitoring their electrochemistry. The PA functionalized asymmetric Pcs were anchored to the ITO surface through chemisorption and their electrochemical properties characterized using cyclic voltammetry to investigate the effects of PA structure on the thermodynamics and kinetics of charge transfer. Ionization energies of the modified ITO surfaces were measured using ultraviolet photoemission spectroscopy.
• Polaske, N. W., McGrath, D. V., & McElhanon, J. R. (2011). Thermally reversible dendronized linear ab step-polymers via "click" chemistry. Macromolecules, 44(9), 3203-3210. doi:http://doi.org/10.1021/ma200296t
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  Abstract: The synthesis and characterization of thermally labile dendronized linear AB step-polymers is described. First through third generation dendritic AB monomers 14a-c containing both a furan and furan-protected maleimide functionality were prepared by the Cu(I)-catalyzed azide-alkyne cycloaddition reaction followed by polymerization via the thermally reversible furan-maleimide Diels-Alder reaction. The assembly, disassembly, and reassembly behavior of linear dendronized step-polymers 16a-c was studied by GPC. © 2011 American Chemical Society.
• Slepian, M. J., Mills, J. L., Slepian, M. J., Mills, J. L., Mertz, J. A., Mcgrath, D. V., Harper, J. L., Geest, J. P., & Ashton, J. H. (2011). Polymeric endoaortic paving: Mechanical, thermoforming, and degradation properties of polycaprolactone/polyurethane blends for cardiovascular applications.. Acta biomaterialia, 7(1), 287-94. doi:10.1016/j.actbio.2010.09.004
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  Polymeric endoaortic paving (PEAP) is a process by which a polymer is endovascularly delivered and thermoformed to coat or "pave" the lumen of the aorta. This method may offer an improvement to conventional endoaortic therapy in allowing conformal graft application with reduced risk of endoleak and customization to complex patient geometries. Polycaprolactone (PCL)/polyurethane (PU) blends of various blend ratios were assessed as a potential material for PEAP by characterizing their mechanical, thermoforming and degradation properties. Biaxial tension testing revealed that the blends' stiffness is similar to that of aortic tissue, is higher for blends with more PCL content, and may be affected by thermoforming and degradation. Tubes of blends were able to maintain a higher diameter increase after thermoforming at higher PCL content and higher heating temperatures; 50/50 blend tubes heated to 55 °C were able to maintain 90% of the diameter increase applied. Delamination forces of the blends ranged from 41 to 235 N m⁻². In a Pseudomonas lipase solution, the 50/50 blend had a 94% lower degradation rate than pure PCL, and the 10/90 blend exhibited no degradation. These results indicate that PEAP, consisting of a PCL/PU blend, may be useful in developing the next generation of endoaortic therapy.
• Ashton, J. H., Mertz, J. A., Harper, J. L., Slepian, M. J., Mills, J. L., McGrath, D. V., & Vande Geest, J. P. (2010). Polymeric Endoaortic Paving (PEAP): Thermomechanical and Degradation Properties of Polycaprolactone/Polyurethane Blends for Cardiovascular Applications," Ashton, J.H.; Mertz, J.A.; Harper, J.L.; Slepian, M.J.; Mills, J.L.; McGrath, D.V.; Vande Geest,† J.P.. Acta Biomaterialia, 7, 287-294. doi:http://doi.org/10.1016/j.actbio.2010.09.004
• Chen, X., Fernando, N., & McGrath, D. V. (2010). Frustration of condensed phase aggregation of naphthalocyanine by dendritic site-isolation. Macromolecules, 43(13), 5512-5514. doi:http://doi/org/10.1021/ma100902m
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  Abstract: The synthesis and aggregation studies of a pair of 3, 4,12,13,21,22,30,31- octasubstituted 2,3-Naphthalocyanine (Ncs) 1 and 2 was reported. The synthetic route leading to these naphthalonitriles started from dimethyl 4,5-dihydroxyphthalate onto which the previously synthesized dendritic alcohols 3 and 4 were introduced through the Mitsunobu protocol. The obtained diesters 6 and 7 were reduced to the corresponding 1,2-dimethanols (8 and 9), and subsequent Swern oxidation provided the disubstituted dendritic phthalaldehydes 10 and 11. Finally, 10 and 11 were converted to naphthalonitriles 12 and 13 through base-promoted condensation with succinonitrile in DMSO. Compounds 1 and 2 were purified by flash column chromatography. Initial molecular aggregation studies were performed in solution as a function of increasing volume fraction of EtOH. The B-bands at 332 and 402 nm exhibited only slight hypochromicity during this change in solvent conditions.
• Mayukh, M., Sema, C. M., Roberts, J. M., & McGrath, D. V. (2010). Solvent-free synthesis of soluble, near-IR absorbing titanyl phthalocyanine derivatives. Journal of Organic Chemistry, 75(22), 7893-7896. doi:http://doi.org/10.1021/jo1011637
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  Abstract: Solvent-free synthesis of a series of alkylthio-substituted titanyl phthalocyanine (TiOPc) derivatives starting from the corresponding phthalonitriles (Pn) is reported. This methodology eliminates the formation of the unmetalated phthalocyanine (H2Pc), a side product that makes purification difficult. The alkylthio groups on the reported derivatives enhance solubility in common organic solvents and shift the absorption to the near-IR region. © 2010 American Chemical Society.
• Ortiz, A., Shanahan, C. S., Sisk, D. T., Perera, S. C., Rao, P., & McGrath, D. V. (2010). Improved iterative synthesis of linearly disassembling dendrons. Journal of Organic Chemistry, 75(18), 6154-6162.
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  PMID: 20738148;Abstract: Figure presented. We report a significant improvement in the synthesis of disassembling dendritic structures by using 4-hydroxy-3-nitrobenzoic acid as the building block. We have prepared multigram quantities of first- through third-generation linearly disassembling dendrons containing a [3-N,4-O]-benzylaryl ether disassembly pathway, capped by a vanillin-derived phenyl allyl ether trigger, and a p-nitrophenoxy (PNP) reporter group. The disassembly process of these materials was initiated by allyl deprotection and monitored by the absorbance of the PNP reporter unit in the UV-vis. Modification of the disassembly conditions for the allyl trigger resulted in decreased disassembly times, decreased incubation time for onset of disassembly from minutes to seconds, and allowed observation of indicative rate differences between generations not seen with the previously reported conditions. © 2010 American Chemical Society.
• Polaske, N. W., McGrath, D. V., & McElhanon, J. R. (2010). Thermally reversible dendronized step-polymers based on sequential Huisgen 1,3-dipolar cycloaddition and diels-alder "click" reactions. Macromolecules, 43(3), 1270-1276. doi:http://doi.org/10.1021/ma902180r
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  Abstract: Thermally labile dendronized AA-BB step polymers are described. First through third generation dendritic bisfuran monomers 6a-6c were prepared in part by the Cu(I)-catalyzed azide-alkyne Huisgen 1,3-dipolar cycloaddition reaction and in turn polymerized by the reversible furan-maleimide Diels-Alder reaction, The Diels-Alder reaction conditions were optimized through end-capping studies with N-phenylmaleimide (7). Dendronized step polymers 10a-10c were then formed from reaction with bismaleimide 9 and their assembly, disassembly, and reassembly behavior studied by GPC. © 2009 American Chemical Society.
• Polaske, N. W., Szalai, M. L., Shanahan, C. S., & McGrath, D. V. (2010). Convergent synthesis of geometrically disassembling dendrimers using Cu(I)-catalyzed C-O bond formation. Organic Letters, 12(21), 4944-4947. doi:http://doi.org/10.1021/ol102081q
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  PMID: 20925328;Abstract: The convergent synthesis of geometrically degradable dendrimers based on the 2,4-bis(hydroxymethyl)phenol subunit is presented. The key step of the synthetic scheme involves the CuI/3,4,7,8-tetramethyl-1,10-phenanthroline- catalyzed coupling of aryl iodides and alcohols. The synthesis and disassembly of these compounds is discussed. © 2010 American Chemical Society.
• Warren, P. D., McGrath, D. V., & Vande Geest, J. P. (2010). Effect of Crosslinker Length and Composition on the Hydrophobicity and Thermomechanical Response of Acrylate-Based Shape-Memory Polymers. Macromolecular Materials and Engineering, 295(4), 386-396. doi:http://dx.doi.org/10.1002/mame.200900348
• Chen, H., Sweet, J. A., Lam, K., Rheingold, A. L., & McGrath, D. V. (2009). Chiral amine-imine ligands based on trans-2,5-disubstituted pyrrolidines and their application in the palladium-catalyzed allylic alkylation. Tetrahedron Asymmetry, 20(14), 1672-1682. doi:http://doi.org/10.1016/j.tetasy.2009.07.010
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  Abstract: A series of amine-imine bidentate ligands based on a trans-2,5-disubstituted pyrrolidine and pyridine moieties have been prepared. The use of these ligands in the palladium-catalyzed allylic alkylation reaction of rac-(E)-1,3-diphenylprop-2-enyl acetate is reported. The results suggest that these ligands are good catalyst precursors for the reaction. Electronic modification on the pyridine ring of the ligands does not have a significant effect on the enantioselectivity of the reaction but does on the reaction rate, while structural modification on either the pyridine or the pyrrolidine moiety affords dramatic changes on the outcome of the stereochemistry. Evidence from various studies suggested that during the palladium-catalyzed allylic alkylation reaction, nucleophilic attack onto the 1,3-diphenylallyl moiety in the transition state occurs mainly trans to the pyridine ring of the less stable conformation of the palladium complexes. © 2009 Elsevier Ltd. All rights reserved.
• Chen, X., Salmon, T. R., & McGrath, D. V. (2009). Asymmetric phthalocyanine synthesis by ROMP-capture-release. Organic Letters, 11(10), 2061–2064. doi:http://doi.org/10.1021/ol900352f
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  Statistical condensation of norbornenyl-tagged phthalonitrile 3 (Pn A) and 4,5-di-4-methoxyphenoxyphthalonitrile 4 (Pn B) followed by ring-opening metathesis polymerization (ROMP) of Pcs AB(3) and B(4) produced asymmetric Pc-appended polymers. Acidic cleavage of the resulting polymers afforded 2,3,9,10,16,17-hexa-(4-methoxyphenoxy)-23-hydroxy Pc 9. A more soluble 2,3,9,10,16,17-hexa-4-pentylphenoxy-23-hydroxy Pc 13 was synthesized by the same strategy and modified with sebacoyl chloride demonstrating that the unmasked hydroxyl site is reactive as a nucleophile.
• Chen, X., Thomas, J., Gangopadhyay, P., Norwood, R. A., Peyghambarian, N., & McGrath, D. V. (2009). Modification of symmetrically substituted phthalocyanines using click chemistry: Phthalocyanine nanostructures by nanoimprint lithography. Journal of the American Chemical Society, 131(38), 13840-13843. doi:http://doi.org/10.1021/ja905683g
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  PMID: 19772367;Abstract: Phthalocyanines (Pcs) are commonly applied to advanced technologies such as optical limiting, photodynamic therapy (PDT), organic field-effect transistors (OFETs), and organic photovoltaic (OPV) devices, where they are used as the p-type layer. An approach to Pc structural diversity and the incorporation of a functional group that allows fabrication of solvent resistant Pc nanostructures formed by using a newly developed nanoimprint by melt processing (NIMP) technique, a variant of standard nanoimprint lithography (NIL), is reported. Copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), a click chemistry reaction, serves as an approach to structural diversity in Pc macrocycles. We have prepared octaalkynyl Pc 1b and have modified this Pc using the CuAAC reaction to yield four Pc derivatives 5a-5d with different peripheral substituents on the macrocycle. One of these derivatives, 5c, has photo-cross-linkable cinnamate residues, and we have demonstrated the fabrication of robust cross-linked photopatterned and imprinted nanostructures from this material. © 2009 American Chemical Society.
• D'Ambruoso, G. D., Ross, E. E., Armstrong, N. R., & Mcgrath, D. V. (2009). Site-isolated, intermolecularly photocrosslinkable and patternable dendritic quinacridones. Chemical communications (Cambridge, England), 3222-3224. doi:http://doi.org/10.1039/B901897B
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  Quinacridone-cored dendrimers with photocrosslinkable cinnamate moieties on the periphery can be patterned down to 5 micron features while retaining luminescence.
• Kernag, C., & McGrath, D. V. (2009). Solution and thin-film aggregation studies of octasubstituted dendritic phthalocyanines. Israel Journal of Chemistry, 49(1), 9-21. doi:http://doi.org/10.1560/IJC.49.1.9
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  Abstract: The synthesis and solution and thin-film characterization of eight octasubstituted dendritic phthalocyanines (Pcs) and their zinc complexes are reported. The Pc chromophore was substituted in the 2,3,9,10,16,17,23,24- positions with three generations of benzylaryl ether dendrons with either a benzyl (3a-3c) or 3,5-di-t-butylbenzyl periphery (3d-3f). Visible spectra in solution (CH2Cl2-EtOH mixtures, toluene, THF, dioxane, acetone, and EtOAc) indicated a varying degree of chromophore aggregation that depended on solvent, dendrimer generation, and whether the Pc was metallated. Variable-concentration visible spectroscopic studies were analyzed using a nonlinear least-squares fitting procedure giving Kd values. These values further quantitated the observations that the t-butyl-substituted dendrimers 3d-3f were all less prone to aggregation in solution than the unsubstituted dendrimers 3a-3c, with a monotonic decrease in Kd across the series 3a → 3b → 3c → 3d → 3e → 3f. Second-generation t-butyl-substituted dendrimer 3f showed little to no aggregation in all solvents studied. Thin-film studies indicated that the largest members of the two dendrimer groups, third-generation 3c and second-generation 3f, were largely monomeric as evidenced by split Q-bands, similar to that seen in dilute CH2Cl2 solution when deposited via spin-coating onto glass slides. The metallated zinc Pcs 4a-4f all exhibited significantly less tendency toward aggregation in both solution and thin-films than their unmetallated analogues.
• McGrath, D. V., Salmon, T. R., & Chen, X. (2009). Asymmetric Phthalocyanine Synthesis by ROMP-Capture-Release. Organic Letters, 11(10), 2061-2064. doi:10.1021/ol900352f
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  Statistical condensation of norbornenyl-tagged phthalonitrile 3 (Pn A) and 4,5-di-4-methoxyphenoxyphthalonitrile 4 (Pn B) followed by ring-opening metathesis polymerization (ROMP) of Pcs AB(3) and B(4) produced asymmetric Pc-appended polymers. Acidic cleavage of the resulting polymers afforded 2,3,9,10,16,17-hexa-(4-methoxyphenoxy)-23-hydroxy Pc 9. A more soluble 2,3,9,10,16,17-hexa-4-pentylphenoxy-23-hydroxy Pc 13 was synthesized by the same strategy and modified with sebacoyl chloride demonstrating that the unmasked hydroxyl site is reactive as a nucleophile.
• D'Ambruoso, G. D., & McGrath, D. V. (2008). Energy harvesting in synthetic dendrimer materials. Advances in Polymer Science, 214(1), 87-147. doi:http://doi.org/10.1007/12_2007_119
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  Abstract: In the past two and a half decades, dendrimers have emerged as a distinct branch of macromolecular chemistry. Tailoring of dendrimer structure yields precise placement of chromophores that can serve as energy harvesters, mimicking photosynthesis. The unique architecture afforded by dendrimers allows for multiple energy harvesters that can transfer their energy to a single core, which is important for optoelectronic applications such as organic light emitting diodes (OLEDs). This review emphasizes the energy transfer characteristics that these dendrimers provide rather then their synthesis. © 2008 Springer-Verlag.
• Plata, R. E., Rogers, H. R., Banister, M., Vohnout, S., & McGrath, D. V. (2008). EAP hydrogels for Pulse Actuated Cell System (PACS) architectures in drug delivery infusion pumps. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 49(1), 836-837.
• Szalai, M. L., Sisk, D. T., Horst, M. J., & McGrath, D. V. (2008). Impact of click chemistry strategies on the synthesis of dendritic systems: Chromophore modification and disassembling systems. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 49(1), 184-.
• Kevwitch, R. M., & McGrath, D. V. (2007). Synthesis and degradation of photolabile dendrimers based on o-nitrobenzyl ether photolabile cores. New Journal of Chemistry, 31(7), 1332-1336. doi:http://doi.org/10.1039/b617289j
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  Abstract: Two dendrimer cores, 1a and 2a, that contain o-nitrobenzyl photolabile moieties, lack hydrolytically sensitive ester linkages and possess three and six sites for dendron attachment, respectively, have been alkylated to provide methylated core analogs 1b and 2b as well as second-generation benzylaryl ether dendrimer 1c and third-generation dendrimer 2c. These dendrimers undergo clean photocleavage as indicated by the evolution of isosbestic points in the UV spectra during photolysis. In addition, the nature of the photodegradation products was confirmed by observing the photolyses by both 1H NMR and GPC. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
• Mcgrath, D. V., & D'ambruoso, G. D. (2007). Energy Harvesting in Synthetic Dendrimer Materials. Advances in Polymer Science, 214, 87-147. doi:10.1007/12_2007_119
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  In the past two and a half decades, dendrimers have emerged as a distinct branch ofmacromolecular chemistry. Tailoring of dendrimer structure yields precise placement of chromophoresthat can serve as energy harvesters, mimicking photosynthesis. The unique architecture afforded bydendrimers allows for multiple energy harvesters that can transfer their energy to a single core,which is important for optoelectronic applications such as organic light emitting diodes (OLEDs).This review emphasizes the energy transfer characteristics that these dendrimers provide rather thentheir synthesis.
• Plata, R. E., Rogers, H. R., Banister, M., Vohnout, S., & McGrath, D. V. (2007). EAP hydrogels for pulse-actuated cell system (PACS) architectures. Proc. SPIE 6524, Electroactive Polymer Actuators and Devices (EAPAD), 6524, 65241T. doi:http://doi.org/10.1117/12.716107
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  Abstract: Electroactuated polymer (EAP) hydrogels based on JEFFAMINE® T-403 and ethylene glycol glycidyl ether (EGDGE) are used in an infusion pump based on the proprietary Pulse Actuated Cell System (PACS) architecture in development at Medipacs LLC. We report here significant progress in optimizing the formulation of the EAP hydrogels to dramatically increase hydrolytic stability and reproducibility of actuation response. By adjusting the mole fraction of reactive components of the formulation and substituting higher molecular weight monomers, we eliminated a large degree of the hydrolytic instability of the hydrogels, decreased the brittleness of the gel, and increased the equilibrium swelling ratio. The combination of these two modifications to the formulation resulted in hydrogels that exhibited reproducible swelling and deswelling in response to pH for a total period of 10-15 hours.
• Szalai, M. L., McGrath, D. V., Wheeler, D. R., Zifer, T., & McElhanon, J. R. (2007). Dendrimers based on thermally reversible furan-maleimide Diels-Alder adducts. Macromolecules, 40(4), 818-823.
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  Abstract: Thermally labile dendrimers based on the reversible furan-maleimide Diels-Alder reaction are described. First through fourth generation benzyl aryl ether based dendrons 3a-d that contained furan moieties at their focal point were allowed to react with bismaleimide central linker 4 to provide the corresponding dendrimers 5-8. Thermal degradation and reassembly of these dendrimers were studied under a variety of conditions and monitored by GPC and NMR. © 2007 American Chemical Society.
• Armstrong, N. R., McGrath, D. V., D'Ambruoso, G. D., Flora, W. H., & Ortiz, A. (2005). Dendritic incorporation of quinacridone: solubility, aggregation, electrochemistry, and solid-state luminescence. Chemical Communications. doi:10.1039/b413684e
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  The first incorporation of quinacridone, a technologically important organic electroluminescent emitter, into dendrimers increases solubility, decreases aggregation, retards heterogeneous electron transfer, and enhances luminescence in condensed phases (powders and thin films).
• Genson, K. L., Holzmueller, J., Vaknin, D., Villavicencio, O. F., McGrath, D. V., & Tsukruk, V. V. (2005). Langmuir monolayers from functionalized amphiphiles with epoxy terminal groups. Thin Solid Films, 493(1-2), 237-248. doi:10.1016/j.tsf.2005.04.091
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  Abstract: We studied Langmuir and Langmuir-Blodgett monolayers from amphiphiles with traditional (carboxylic) and bulky functionalized (epoxy) terminal groups at the air-water and air-solid interfaces. We demonstrated that the molecules with a central azobenzene fragment and carboxylic (AA-1 molecule) and bulky epoxy (AE-1 molecule) polar groups formed orthorhombic unit cells with larger than expected area per alkyl tail. The higher order of symmetry indicated by the appearance of higher Qxy peaks revealed that the alkyl tails formed a herringbone structure with limited long range ordering. In the condensed monolayer, the azobenzene group of the AA-1 molecules was oriented vertically in contrast to the AE-1 molecule that was significantly tilted. In addition, the presence of the bulky epoxy focal groups caused a less dense lateral packing of the azobenzene groups. We suggest that the bulky focal group causes intramonolayer packing which can enhance the ability of the chemically grafted azobenzene groups for photoisomerization. © 2005 Elsevier B.V. All rights reserved.
• Genson, K. L., Holzmuller, J., Villacencio, O. F., McGrath, D. V., Vaknin, D., & Tsukruk, V. V. (2005). Langmuir and grafted monolayers of photochromic amphiphilic monodendrons of low generations. Journal of Physical Chemistry B, 109(43), 20393-20402. doi:10.1021/jp0524678
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  PMID: 16853639;Abstract: Four generations of monodendrons with multiple dodecyl alkyl tails (AA-N, N representing number of alkyl tails from 1 to 8), an azobenzene spacer group, and a carboxylic acid polar head have been studied at the air-water and air-solid interface using AFM, GIXD, X-ray reflectivity, and UV - vis spectrometry. The one and two tail molecules formed orthorhombic lateral packing with long-range intramonolayer ordering. Good agreement between molecular models and thickness measurements indicated that the one and two tail molecules orient along the surface normal. The increase in the cross-sectional mismatch caused by the presence of the multiple chains for the higher generations disrupted the long-range ordering and forced the alkyl tails to adopt quasi-hexagonal structure. The higher generations (AA-4 and AA-8) formed a kinked structure with the alkyl tails oriented perpendicular to the surface with the azobenzene group tilted at a large degree toward the surface. The photoisomerization behavior in dilute solutions, at the air-water interface, and for grafted layers demonstrated that lower generation monodendrons maintained the photochromic behavior after chemical grafting to the silicon substrates, although the confinement of the molecules in monolayers significantly increased the reorganization time. © 2005 American Chemical Society.
• McGrath, D. V. (2005). Dendrimer disassembly as a new paradigm for the application of dendritic structures. Molecular Pharmaceutics, 2(4), 253-263. doi:10.1021/mp050047x
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  PMID: 16053328;Abstract: We present an overview of an entirely new concept in nanotechnology, dendrimer disassembly. Dendrimer disassembly is a process that relies on a single triggering event to initiate multiple cleavages throughout a dendritic structure that result in release of individual dendrimer subunits or larger dendrimer fragments. The potential of this process lies in (1) the nature of dendrimers as covalent assemblages of active species, and using the chemistry of disassembly to release these species into a system; and (2) the role of dendritic components of a system in influencing solubility, energy harvesting, or insulating capabilities, etc., and using the chemistry of disassembly to reverse those contributions to a system. This is a powerful construct, in that dendrimers and dendritic structures can be made up of a wide variety of subunits, compatibilized with many different environments, and incorporated into countless systems. We anticipate that dendritic materials with disassembly capabilities will (a) be useful for traditional polymer degradation technologies and (b) have potential applications in nanotechnology, biomedicine, sensors, etc. © 2005 American Chemical Society.
• Ortiz, A., Flora, W. H., D'Ambruoso, G. D., Armstrong, N. R., & McGrath, D. V. (2005). Dendritic incorporation of quinacridone: solubility, aggregation, electrochemistry, and solid-state luminescence. Chemical communications (Cambridge, England), 444-446. doi:10.1039/B413684E
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  The first incorporation of quinacridone, a technologically important organic electroluminescent emitter, into dendrimers increases solubility, decreases aggregation, retards heterogeneous electron transfer, and enhances luminescence in condensed phases (powders and thin films).
• Shanahan, C. S., & McGrath, D. V. (2005). Synthesis and characterization of BHT-derived tert-butyl dendrons. Journal of Organic Chemistry, 70(3), 1054-1056. doi:10.1021/jo0483419
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  PMID: 15675869;Abstract: (Chemical Equation Presented) A series of 3,5-poly(aryl ether) dendrons was prepared up to the third generation using inexpensive 3,5-di-tert-butyl-4- hydroxytoluene (BHT, 1) as a starting material.
• Liao, L., Stellacci, F., & McGrath, D. V. (2004). Photoswitchable Flexible and Shape-Persistent Dendrimers: Comparison of the Interplay between a Photochromic Azobenzene Core and Dendrimer Structure. Journal of the American Chemical Society, 126(7), 2181-2185. doi:http://doi.org/10.1021/ja036418p
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  PMID: 14971953;Abstract: Two analogous classes of dendrimers with a single azobenzene moiety at the core have been prepared. Flexible benzyl aryl ether dendrimers 1a-e were obtained in good yields by direct alkylation of diphenolic azobenzene 3 with benzyl aryl ether dendrons [G-n]-Br (n = 0-4). In rigid dendrimers 2a-e, the azobenzene configurational switch was linked to phenylacetylene dendrons through acetylenic linkages to maintain the shape-persistent nature of these dendrimers. A comparison of these two different classes of dendrimers with azobenzene cores reveals a difference in the properties of the photochromic moiety upon dendritic incorporation as well as a significant difference in the photomodulation of dendrimer properties. The E → Z photoisomerization quantum yield decreased markedly with increasing generation for dendrimers 1a-e but only slightly for dendrimers 2a-e. However, increasing generation did not significantly alter thermal isomerization kinetics or activation barriers. The hydrodynamic volumes of azobenzene-containing dendrimers 2b-e were significantly modulated when the azobenzene unit is subjected to irradiation, while those of dendrimers 1b-e were only slightly affected.
• Szalai, M. L., & McGrath, D. V. (2004). Phototriggering of geometric dendrimer disassembly: An improved synthesis of 2,4-bis(hydroxymethyl)phenol based dendrimers. Tetrahedron, 60(34), 7261-7266. doi:10.1016/j.tet.2004.06.078
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  Abstract: Dendrimers capable of phototriggered disassembly were prepared up to the second-generation using an improved synthesis of 2,4-bis(hydroxymethyl)phenol based dendrimers. It was found that disassembly proceeds to 75-80% completion after 2 h of irradiation at 310 nm for all molecules studied. The lack of complete reaction is attributed to an inefficient photochemical deprotection process rather than the disassembly itself. © 2004 Elsevier Ltd. All rights reserved.
• Kernag, C. A., & McGrath, D. V. (2003). Non-aggregating octasubstituted dendritic phthalocyanines. Chemical Communications, 9(9), 1048-1049. doi:10.1039/B301157G
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  Abstract: Eight poly(aryl) ether dendritic wedges attached to the periphery of a phthalocyanine significantly decreases self-association of these chromophores in solution and the condensed state.
• Li, S., Szalai, M. L., Kevwitch, R. M., & McGrath, D. V. (2003). Dendrimer disassembly by benzyl ether depolymerization. Journal of the American Chemical Society, 125(35), 10516-10517. doi:http://doi.org/10.1021/ja0349960
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  PMID: 12940723;Abstract: The disassembly of dendritic structures was realized by a cascade cleavage reaction triggered by an initially stimulated group in the dendrimer periphery. A depolymerizable backbone was engineered into prototypical dendritic structures. Evidence for the completion of the disassembly process is provided by the absorbance peak of the p-nitrophenoxide ion that was intentionally installed at the focal point of the dendrons. Observation of the UV spectra during the disassembly process supports a stepwise cascade cleavage proceeding from the periphery into the core. Copyright © 2003 American Chemical Society.
• Szalai, M. L., Kevwitch, R. M., & McGrath, D. V. (2003). Geometric Disassembly of Dendrimers: Dendritic Amplification. Journal of the American Chemical Society, 125(51), 15688-15689. doi:http://doi.org/10.1021/ja0386694
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  PMID: 14677927;
• Whitten, D. G., Schanze, K. S., Penner, T. L., Mcgrath, D. V., & Armitage, B. A. (2003). Langmuir Special Issue in Memory of David F. O'Brien. Langmuir, 19(16), 6339-6341. doi:10.1021/la0302495
• Bieging, A., Liao, L., & McGrath, D. V. (2002). Hydrobenzoin-based rigid chiral polymer. Chirality, 14(2-3), 258-263.
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  PMID: 11835572;Abstract: We prepared a rigid, chiral polymer (1) from optically active hydrobenzoin-based subunits. Nonracemic monomer units 6 and 8 were prepared by asymmetric dihydroxylation (AD) methodology and polymerization was carried out under Sonagashira coupling conditions. Polymer I was obtained in good yield with a molecular weight Mn = 5,100 (PDI = 2.3). Modeling suggests that polymer 1 could form a stable helical mainchain conformation in solution or the solid state. The chiroptical data of the polymer and a low-molecular weight model compound (9) are compared. © 2002 Wiley-Liss, Inc.
• Genson, K. L., Vaknin, D., Villacencio, O., McGrath, D. V., & Tsukruk, V. V. (2002). Microstructure of amphiphilic monodendrons at the air-water interface. Journal of Physical Chemistry B, 106(43), 11277-11284.
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  Abstract: Grazing incident X-ray diffraction and X-ray reflectivity have been performed on Langmuir monolayers of low generation monodendrons containing a crown-ether polar group, azobenzene spacer, and varying number of peripheral alkyl chains of 1, 2, 4, and 8. We observe that the cross-sectional mismatch between the bulky polar head and the alkyl tails has a profound effect on the local ordering of the alkyl tails. It is found that the alkyl chains in a single-tail molecule are significantly tilted away from the surface normal. The tilt is eliminated in molecules with two or more alkyl chains where the cross-sectional mismatch is in favor of the peripheral tails. The molecule with one tail possesses a supercell orthorhombic packing caused by structural nonequivalency on the neighboring tails. The two- and four-tail molecules form a mixed structure best described by a quasi-hexagonal unit cell, and the eight-tail molecule forms a more stable hexagonal unit cell. Peripheral tails for these molecules are in standing-off orientation. We suggest that the steric constraints cause lower correlations and a staggered packing structure of monolayers from the eight-tail molecule. We suggest that branching alkyl tails off the same phenyl ring and the presence of the phenyl rings in the vicinity of the branching are limiting factors on the chain packing at the air-water interface in monodendrons with multiple peripheral tails. We conclude that a significant portion of the molecules is submerged in the water subphase and possesses a "kink" shape.
• Kevwitch, R. M., & McGrath, D. V. (2002). Synthesis of photolabile dendrimer cores. Synthesis, 1171-1176.
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  Abstract: Two dendrimer cores, 5 and 12, containing o-nitrobenzyl photolabile moieties have been synthesized from piperonal in five and eight steps, respectively. Methylated core analogs 6 and 13 undergo clean photocleavage as indicated by the evolution of isosbestic points in the UV spectra during photolysis and the observation of degradation products by 1H NMR. These dendrimer cores serve as precursors to dendrimer-based photodegradable materials.
• Larson, K., Vaknin, D., Villavicencio, O., McGrath, D., & Tsukruk, V. V. (2002). Molecular packing of amphiphiles with crown polar heads at the air-water interface. Journal of Physical Chemistry B, 106(29), 7246-7251.
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  Abstract: An amphiphilic compound containing a benzyl-15-crown-5 focal point, azobenzene spacer, and a dodecyl tail as a peripheral group has been investigated at the air-water interface. X-ray reflectivity and grazing incident diffraction (XGID) were performed on the Langmuir monolayers to elucidate molecular packing and orientation of molecular fragments for the compound with mismatch between cross-sectional areas of hydrophobic and hydrophilic segments. At high surface pressure, we observed intralayer packing of the alkyl tails with doubling parameters of the conventional orthorhombic unit cell (supercell) and long-range positional ordering. High tilt of the alkyl tails of 58° from the surface normal was a signature of molecular packing caused by a large mismatch between the cross-sectional areas of the polar head (45 Å2) and the alkyl tail (20 Å2).
• Liao, L., Junge, D. M., & McGrath, D. V. (2002). Photochromic dendrimers containing six azobenzenes. Macromolecules, 35(2), 319-322.
• Mcgrath, D. V. (2002). Dendrimer isolation of chromphores for photonic applications. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 43(2).
• Peleshanko, S., Sidorenko, A., Larson, K., Villavicencio, O., Ornatska, M., McGrath, D. V., & Tsukruk, V. V. (2002). Langmuir-Blodgett monolayers from lower generation amphiphilic monodendrons. Thin Solid Films, 406(1-2), 233-240.
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  Abstract: Amphiphilic monodendrons of lower generations, AD12-N, containing a benzyl-15-crown-5 polar focal point, photochromic spacer and different number of dodecyl tails as peripheral groups (n = 1-8) have been investigated for their ability to form uniform monolayers at solid surfaces. The surface pressure-area behavior, photomechanical behavior and the morphology of the monomolecular films were investigated. We observed that all compounds studied are capable of forming stable Langmuir and Langmuir Blodgett monolayers, with virtually flat packing of molecules. Higher generation dendrimers form very uniform monolayers, without the usual domain microstructure. For AD12-4 monolayer on solid support, we observed stripped microstructure with several layers (3-6) bundled together. The periodicity of this structure of 8 nm was close to layered spacing, obtained from X-ray data for bulk material. For this compound, we proposed the model of double-layered packing of the molecules, with partial overlapping of the central segments and suggested that deposition on a solid substrate resulted in changing orientation of molecular fragments. Fast reversible photochromic response was observed for all monolayers with a conversion level of 50%. © 2002 Elsevier Science B.V. All rights reserved.
• Sidorenko, A., Houphouet-Boigny, C., Villavicencio, O., McGrath, D. V., & Tsukruk, V. V. (2002). Low generation photochromic monodendrons on a solid surface. Thin Solid Films, 410(1-2), 147-158.
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  Abstract: Zeroth through third generations of amphiphilic monodendrons containing a benzyl-15-crown-5 polar focal point, photochromic spacer, and alkyl tails as peripheral groups have been investigated for their ability to form photoresponsive surface monolayers. Thickness measurements, scanning probe microscopy, and molecular modeling were used to determine the microstructure of the monolayers. The tilted molecular packing of dendrons in the monolayers is proposed with bulky dendritic shell prohibiting dense packing of azobenzene groups and the aggregate formation. The two-stage trans-cis isomerization was observed for the photochromic monodendron layers composed of various generation dendrons. Fast changes within the first several minutes occurred in the azobenzene-containing monodendrons until the conversion of trans-cis isomerization reaches 13-33%. Then lateral steric hindrances in the monolayer decreases the transformation rate by three orders of magnitude. Diffusion limited intralayer reorganization is suggested to be a limiting factor in the rate of photoisomerization changes. © 2002 Elsevier Science B.V. All rights reserved.
• Tsukruk, V. V., Luzinov, I., Larson, K., Li, S., & McGrath, D. V. (2001). Intralayer reorganization of photochromic molecular films. Journal of Materials Science Letters, 20(9), 873-876.
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  Abstract: Azobenzene-containing amphiphilic dendrimer was used to fabricate a photosensitive monolayer. A crown-ether moiety served as a polar head and a polyether fragment with long-chain alkyl tails providing hydrophobicity for an overall amphiphilic character. The architecture exhibited two dissimilar bulky terminal fragments.
• Junge, D. M., Wu, M., McElhanon, J. R., & McGrath, D. V. (2000). Synthesis and chiroptical analysis of optically active chiral shell dendrons. Journal of Organic Chemistry, 65(17), 5306-5314.
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  Abstract: We have prepared a series of chiral dendrons (1-4) in which chiral subunits are placed in individual generational shells at varying distances from the focal point. The optical activity of these chiral dendritic structures is successfully modeled using structurally similar low-molecular weight model compounds. In dendrons 1a and 1b a chiral subunit is directly adjacent to the focal point, whereas in dendrons 2, 3, and 4a,b the chiral subunits are incorporated in the interior of the dendron. A marked difference in optical activity between the former (1a and 1b) and latter (2, 3, 4a,b) dendrons is mirrored in the optical activities of model compounds 12a, 12b, 19a, and 19b. These model compounds directly mimic the surrounding constitution of the chiral subunits in the dendrons. This successful analysis of the chiroptical data using low-molecular weight model compounds suggests that these dendrons do not possess conformational order in solution.
• Liao, L., & McGrath, D. V. (2000). Shape-persistent azobenzene-containing dendrimers. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 41(1), 870-.
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  Abstract: Azobenzene-containing shape-persistent dendrimers were synthesized to address the effect of the dendrimer subunit on the behavior of well-defined systems. The resulting dendrimers have rigid structures with phenylacetylene subunits. The properties of the dendrimers allow comparison with previously-prepared flexible azobenzene-containing dendrimers.
• McElhanon, J. R., & McGrath, D. V. (2000). Toward chiral polyhydroxylated dendrimers. Preparation and chiroptical properties. Journal of Organic Chemistry, 65(11), 3525-3529.
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  Abstract: Four dendrimers (1b-4b) containing chiral vicinal diol-based subunits were prepared from their acetonide-protected precursors (1a-4a). The optical activity of these chiral dendritic structures was successfully modeled using structurally similar, low molecular weight model compounds. Using the [Φ](d) values of the low molecular weight model compounds 5b-7b, we calculated [Φ](d) values for dendrimers 1b-4b that agree to within 4.5% of the observed values. Agreement between the optical activity of the model compounds and that of the dendrimers leads to the conclusion that the conformational equilibria of the dendrimer subunits are not perturbed relative to those of the model compounds.
• Radhakrishnan, U., & McGrath, D. V. (2000). Synthesis of spiropyran based photoresponsive dendrimers. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 41(1), 883-884.
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  Abstract: The polarity of the open form of spiropyrans is suitable for use as surfactants and for controlling the hydrophilicity of the dendrimer surface with the use of light. Spiropyrans as a peripheral unit of dendrimer with a non-polar inner core will lead to the formation of macromolecules with photolytically-controlled amphiphilic character. In this connection, spiropyran subunits were introduced on the surface of dendrimers prepared using the convergent synthetic strategy to modify the dendrimers' properties.
• Sheng, L. i., & McGrath, D. V. (2000). Effect of macromolecular isomerism on the photomodulation of dendrimer properties. Journal of the American Chemical Society, 122(28), 6795-6796.
• Sheng, L. i., & McGrath, D. V. (2000). Macromolecular isomers of azobenzene-containing photochromic dendrimers. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 41(1), 861-862.
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  Abstract: Second generation dendrimer 2 with single azobenzene moieties attached to the periphery of each dendron is prepared by using protection-deprotection methodology. This modified convergent method using key intermediates methyl 3-benzyloxy-5-hydroxybenzoate (4) and methyl 3-allyloxy-5-hydroxybenzoate (8) is used widely in precise dendrimer synthesis. Preparation of higher generation of dendrimers with only one azobenzene moiety in the exterior of each dendron is ongoing. The complete comparison of physical properties between the two types of dendrimers 1 and 2 is investigated.
• Sheng, L. i., & McGrath, D. V. (2000). Olefin metathesis for dendrimer assembly. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 41(1), 865-.
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  Abstract: Conditions for the self-metathesis assembly of dendrons with alkenyl focal points into dendrimers are developed. Assembly of more complex central cores is the subject of current efforts. Olefin metathesis has become a powerful method in organic synthesis. Several ruthenium-based alkylidiene complexes have led to considerable success in the ring-opening metathesis and ring-closing metathesis reactions in application to the total synthesis of natural products. A preliminary study on the use of metathesis to assemble benzyl aryl ether dendrimers is reported. Self-metathesis yielding dendrimers is observed and the effects of solvent, temperature and reaction conditions on final product yield is optimized.
• Sidorenko, A., Houphouet-Boigny, C., Greco, A. C., Villavicencio, O., Hashemzadeh, M., McGrath, D. V., & Tsukruk, V. V. (2000). Langmuir monolayers from azobenzene-containing dendrons. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 41(2), 1487-1488.
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  Abstract: Monolayer films were fabricated from photochromic monodendrons with amphiphilic character. Amphiphilicity was established by a hydrophilic focal point (crown-ether) and hydrophilic tails (alkyl chains) that flank a photochromic azobenzene moiety. The monolayer forming properties of four generations of dendrons along with both stearic acid and a reference azobenzene compound with a carboxylic acid focal point group were determined.
• Sidorenko, A., Houphouet-Boigny, C., Villavicencio, O., Hashemzadeh, M., McGrath, D. V., & Tsukruk, V. V. (2000). Photoresponsive Langmuir monolayers from azobenzene-containing dendrons. Langmuir, 16(26), 10569-10572.
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  Abstract: The monolayer-forming properties of four generations of azobenzene-containing dendrons were investigated. The photochromic dendron for monolayer formation was used because of the potential ability to suppress crystallization of the photochromic fragments. All dendritic compounds can be spread on an air-water interface to form a stable monolayer. There ia a systematic increase in the cross-sectional area per molecule with increasing number of alkyl tails in the outer shell of dendrons.
• Smet, M., Liao, L., Dehaen, W., & McGrath, D. V. (2000). Photolabile dendrimers using o-nitrobenzyl ether linkages. Organic Letters, 2(4), 511-512.
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  Abstract: (Formula presented) Benzyl aryl ether dendrimers containing photosensitive, veratryl-based o-nitrobenzyl AB linkages (bold bonds) were prepared to the third generation and shown to undergo site-specific degradation when irradiated with ultraviolet light.
• Junge, D. M., & McGrath, D. V. (1999). Photoresponsive azobenzene-containing dendrimers with multiple discrete states. Journal of the American Chemical Society, 121(20), 4912-4913.
• Kernag, C. A., Bobbitt, J. M., & McGrath, D. V. (1999). Mild and convenient oxidation of aromatic heterocyclic primary alcohols by 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxoammonium perchlorate. Tetrahedron Letters, 40(9), 1635-1636.
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  Abstract: Hydroxymethyl substituted aromatic heterocycles, including pyridines, furans, and thiophenes, are oxidized to the corresponding aldehydes in excellent yields by 4-acetylamino-2,2,6,6-tetramethylpiperidine-1- oxoammonium perchlorate (1) with minimal workup.
• McGrath, D. V., & Junge, D. M. (1999). Driving dendrimers with light: Dendrimers with azobenzene central linkers. Macromolecular Symposia, 137, 57-65.
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  Abstract: Several new classes of azobenzene-containing dendrimers have been prepared and characterized. Three central linker azobenzenes, p-(p'-hydroxyphenylazo)phenol (A), aniline p-(p'-chlorocarbonylphenylazo)benzoyl chloride (B), and p-(p'-aminophenylazo) (C) were reacted with the appropriate dendritic fragment ([Gn]Br for A and C; [Gn]OH for B) to yield dendrimers 1-3 of varying generational size. The photoresponsive characterization of these dendrimers illustrates the insensitivity of the photoresponsive behavior of the azobenzene with respect to the nature of the attached dendritic fragment.
• McGrath, D. V., Junge, D. M., Cheng, A., & D'Ambruoso, G. (1999). Effect of covalently incorporated azobenzenes on dendrimers. Materials Research Society Symposium - Proceedings, 543, 319-326.
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  Abstract: Several new azobenzene-containing dendritic molecules have been prepared and characterized. The photoresponsive characterization of these dendrimers illustrates the insensitivity of the photochromic behavior of the azobenzene with respect to the nature of the attached dendritic fragment.
• Sheng, L. i., Sikder, S., & McGrath, D. V. (1999). Synthesis of amphiphilic photoresponsive dendrons. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 40(2), 267-268.
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  Abstract: Amphiphilic dendritic structures having a photoresponsive azobenzene moiety linked between a hydrophilic crown ether receptor and a hydrophobic dendritic sector were prepared and characterized. These dendritic structures exhibit typical azobenzene moiety on the phase behavior is investigated.
• Bett, J. S., Kunz, H. R., Aldykiewicz Jr., A. J., Fenton, J. M., Bailey, W. F., & McGrath, D. V. (1998). Platinum-macrocycle co-catalysts for the electrochemical oxidation of methanol. Electrochimica Acta, 43(24), 3645-3655.
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  Abstract: Metal phthalocyanines (Fe, Co, Ni and Sn) and ruthenium tetramethylcyclam 14 and 15 were studied as cocatalysts for methanol oxidation on platinum supported catalysts. The formation of well defined monolayers of the adsorbed complexes was inferred from the Langmuirian form of the adsorption isotherms in solutions of macrocycles. The coverage at monolayer levels was low, e.g. 1.25 to 2.25 × 1013 molecules cm-2 or 400 to 800 Å2 molecule-1. Enhancement for the methanol oxidation reaction was observed for Pt co-catalyzed with Sn phthalocyanine and Ru tetramethylcyclam. Ru tetramethylcyclam showed an enhancement for methanol oxidation on a per unit weight basis over pure Pt, approaching the activity of PtRu at lower potentials. Increasing the size of the nitrogen ring from 14 to 15 resulted in a lower redox potential and increase in the activity of methanol oxidation. The activity of Pt co-catalyzed with Ru TMC 15 decreased with time suggesting that the macrocycle was desorbing from the supported catalyst surface. © 1998 Elsevier Science Ltd. All rights reserved.
• Hashemzadeh, M., & McGrath, D. V. (1998). Toward photoresponsive dendritic self-assembly. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 39(2), 338-339.
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  Abstract: Tapered dendritic structures with a crown ether receptor moiety and a hydrophobic dendritic sector linked through an azobenzene were prepared and characterized. The dendritic structures exhibit typical azobenzene photoresponsive behavior in solution.
• Junge, D. M., & McGrath, D. V. (1998). Photoresponsive dendrimers. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 39(2), 340-341.
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  Abstract: The photoresponsive behavior of dendrimers with methyl ester exteriors and azobenzene linkers were studied. Saponification of dendrimer 6 was also accomplished to provide a water soluble dendrimer with a hydrophobic interior.
• Junge, D. M., & McGrath, D. V. (1998). Synthesis of optically active chiral shell dendrons. Tetrahedron Letters, 39(13), 1701-1704.
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  Abstract: We present the preparation of a series of chiral dendrons, in which chiral subunits are placed in individual generational shells at increasing distances from the focal point, by a combination of convergent and divergent dendrimer synthesis methods. Analysis of chiroptical data suggests that these dendrons do not possess conformational order in solution.
• McGrath, D. V., Junge, D. M., McElhanon, J. R., & Hashemzadeh, M. (1998). Driving dendrimers with light. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 39(2), 281-282.
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  Abstract: New dendrimers with azobenzene central linkers were prepared and their photoresponsive behavior demonstrated. The rates and activation energies of the thermal cis-trans isomerization of a series of dendrimers of increasing size illustrate the insensitivity of the photoresponsive behavior of the azobenzene with respect to the nature of the attached dendritic fragment.
• Mcgrath, D. V., & Mcelhanon, J. R. (1998). Constitution, configuration, and the optical activity of chiral dendrimers. Journal of the American Chemical Society, 120(8), 1647-1656. doi:10.1021/ja970150i
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  Three series of zeroth to second generation chiral dendrimers, 7−9, 10−12, and 13−15, were prepared by convergent methods using chiral, nonracemic AB2 monomers 1, 2, and 3, respectively. Chiroptical data revealed a significant change in molar rotation per subunit ([Φ]D/n) as dendrimer generation increased for dendrimers 7−9 and 10−12, but not for dendrimers 13−15, a possible indication of chiral conformational order in the former two series of dendrimers, but not in the last. However, the optical activities ([Φ]D) of low-molecular-weight model compounds 16 (+262) and 17 (+122), prepared to simulate different regions of the dendrimer structure, suggest that as generation size increases slight constitutional changes have a strong effect on the chiroptical properties of the dendrimer subunits. Using the [Φ]D values of these and other (18−23) low-molecular-weight model compounds, we calculated [Φ]D values for dendrimers 7−15 that agree within 14% of the observed values. Agreement between the optical activity ...
• Mcgrath, D. V., Junge, D. M., D'ambruoso, G., & Cheng, A. (1998). Effect of Covalently Incorporated Azobenzenes on Dendrimers. MRS Proceedings, 543, 319-326. doi:10.1557/proc-543-319
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  Several new azobenzene-containing dendritic molecules have been prepared and characterized. The photoresponsive characterization of these dendrimers illustrates the insensitivity of the photochromic behavior of the azobenzene with respect to the nature of the attached dendritic fragment.
• Junge, D. M., & McGrath, D. V. (1997). Photoresponsive dendrimers. Chemical Communications, 857-858.
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  Abstract: Benzyl aryl ether dendrimers with azobenzene central linkers undergo reversible cisltrans isomerization of the azobenzene moiety upon exposure to ultraviolet light.
• McElhanon, J. R., & McGrath, D. V. (1997). Constitution, configuration, and the optical activity of chiral dendrimers. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 38(1), 278-279.
• McElhanon, J. R., Wu, M., Escobar, M., Chaudhry, U., Hu, C., & McGrath, D. V. (1997). Asymmetric Synthesis of a Series of Chiral AB₂ Monomers for Dendrimer Construction. Journal of Organic Chemistry, 62(4), 908-915.
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  Abstract: Efficient preparation of a series of four chiral, nonracemic AB2 monomers suitable for the construction of dendrimers is presented. Monomers 1-4 possess the common structural features of a diphenolic moiety and a benzylic or aliphatic hydroxyl which render these molecules suitable for convergent dendrimer synthesis. The same basic, high-yielding, five-step sequence is employed for 1-4. Stilbene derivatives 13 and 14 are prepared by a Horner-Wadsworth-Emmons modified Wittig reaction between 3,5- or 3,4-bis(benzyloxy)benzaldehyde (8 and 10) and an ester-substituted benzylphosphonate (11 or 12). Cinnamate derivatives 21 and 22 are prepared similarly from 8 and 10 and triethyl phosphonoacetate. Chirality is introduced in the form of a 1,2-diol unit by Sharpless asymmetric dihydroxylation (AD) (>97% ee in all cases). Protection of the 1,2-diols as their acetonide derivatives provides dioxolane intermediates 17, 18, 25, and 26. Reduction of the ester groups followed by hydrogenolysis of the benzyl ethers yields AB2 monomers 1-4 in 57-67% overall yield from 8 and 10.
• Nelson, D. W., Gypser, A., Ho, P. T., Kolb, H. C., Kondo, T., Kwong, H., McGrath, D. V., Rubin, A. E., Norrby, P., Gable, K. P., & Sharpless, K. B. (1997). Toward an understanding of the high enantioselectivity in the osmium-catalyzed asymmetric dihydroxylation. 4. Electronic effects in amine-accelerated osmylations. Journal of the American Chemical Society, 119(8), 1840-1858.
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  Abstract: Electronic effects in osmylation reactions accelerated by pyridine and quinuclidine derivatives were investigated by varying the substituents on the amine ligand as well as on the alkene substrate. Ligand substituent effects were gauged by determination of the equilibrium constants for coordination of the amines to OsO4, evaluation of structural properties and reduction potentials of the amine-OsO4 complexes, and analysis of the kinetics of osmylations in the presence of the amines. Substrate substituent effects were gauged by kinetic Hammett studies using several different amine/alkene combinations. Nonlinear Hammett relationships resulting from alkene substituent effects were observed, and the deviation from a linear free energy relationship was found to depend on the structure, binding capacity, and concentration of the amine. The results were evaluated in terms of the contending '[3 + 2]' and '[2 + 2]' mechanisms currently under consideration. A change in mechanism that depends on the structural and electronic properties of both alkene and amine is proposed.
• Sweet, J. A., Cavallari, J. M., Price, W. A., Ziller, J. W., & McGrath, D. V. (1997). Synthesis and characterization of new amine-imine ligands based on trans-2,5-disubstituted pyrrolidines. Tetrahedron Asymmetry, 8(2), 207-211.
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  Abstract: We present a modular synthesis of a new class of chiral N,N-chelating ligands containing the C2-symmetric trans-2,5-disubstituted pyrrolidine moiety linked to a pyridine ring. (-)-2-[(2R,5R)-2,5-Dimethylpyrrolidin-1-ylmethyl]pyridine (11, (R,R)-MePMP), (-)-2-[2((2R,5R)-2,5-dimethylpyrrolidin- (12, (R,R)-MePEP), and (+)-2-[(2R,5R)-2,5-diphenylpyrrolidin-1-ylmethyl]pyridine (13, (R,R)-PhPMP) have been prepared. The X-ray structure of the (Λ3-allyl)Pd complex of (R,R)-MePMP (11) is reported.
• Wu, M. J., Mcgrath, D. V., Mcelhanon, J. R., Hu, C. L., Escobar, M., & Chaudhry, U. (1997). ASYMMETRIC SYNTHESIS OF A SERIES OF CHIRAL AB2 MONOMERS FOR DENDRIMER CONSTRUCTION. Journal of Organic Chemistry, 62(4), 908-915. doi:10.1021/jo961587w
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  Efficient preparation of a series of four chiral, nonracemic AB2 monomers suitable for the construction of dendrimers is presented. Monomers 1−4 possess the common structural features of a diphenolic moiety and a benzylic or aliphatic hydroxyl which render these molecules suitable for convergent dendrimer synthesis. The same basic, high-yielding, five-step sequence is employed for 1−4. Stilbene derivatives 13 and 14 are prepared by a Horner−Wadsworth−Emmons modified Wittig reaction between 3,5- or 3,4-bis(benzyloxy)benzaldehyde (8 and 10) and an ester-substituted benzylphosphonate (11 or 12). Cinnamate derivatives 21 and 22 are prepared similarly from 8 and 10 and triethyl phosphonoacetate. Chirality is introduced in the form of a 1,2-diol unit by Sharpless asymmetric dihydroxylation (AD) (>97% ee in all cases). Protection of the 1,2-diols as their acetonide derivatives provides dioxolane intermediates 17, 18, 25, and 26. Reduction of the ester groups followed by hydrogenolysis of the benzyl ethers yields...
• McElhanon, J. R., Wu, M., Escobar, M., & McGrath, D. V. (1996). Toward chiral dendrimers with highly functionalized interiors. Dendrons from synthetic AB₂ monomers. Macromolecules, 29(27), 8979-8982.
• McElhanon, J., Wu, M., Escobar, M., & McGrath, D. V. (1996). Synthesis of optically active chiral dendrimers with 1,2-diol linkages. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 37(2), 495-496.
• McGrath, D. V., Wu, M., & Chaudhry, U. (1996). An approach to highly functionalized dendrimers from chiral, non-racemic synthetic monomers. Tetrahedron Letters, 37(34), 6077-6080.
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  Abstract: An approach to dendrimers with highly functional interiors constructed from chiral, non-racemic hydrobenzoin monomer units is presented. An optically pure monomer unit is prepared using asymmetric dihydroxylation (AD) and a representative dendrimer is constructed by a convergent growth strategy.
• Wu, M. J., Mcgrath, D. V., & Chaudhry, U. (1996). AN APPROACH TO HIGHLY FUNCTIONALIZED DENDRIMERS FROM CHIRAL, NON-RACEMIC SYNTHETIC MONOMERS. Tetrahedron Letters, 37(34), 6077-6080. doi:10.1016/0040-4039(96)01295-6
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  Abstract An approach to dendrimers with highly functional interiors constructed from chiral, non-racemic hydrobenzoin monomer units is presented. An optically pure monomer unit is prepared using asymmetric dihydroxylation (AD) and a representative dendrimer is constructed by a convergent growth strategy.
• McGrath, D. V., & Grubbs, R. H. (1994). The mechanism of aqueous ruthenium(II)-catalyzed olefin isomerization. Organometallics, 13(1), 224-235.
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  Abstract: Olefin isomerization of allylic ethers and alcohols is catalyzed by RuII(H2O)6(tos)2 (tos = p-toluenesulfonate) (1) under mild conditions in aqueous solution to yield the corresponding carbonyl compounds. Non-allylic olefins are also isomerized, although homoallylic alcohols exhibit stability toward isomerization. An exclusive 1,3-hydrogen shift is observed in the isomerization of allyl-1,1-d2 alcohol to propionaldehyde-1,3-d2 and allyl-1,1-d2 methyl ether to 1-propenyl-1,3-d2 methyl ether by 1 in aqueous solution. The presence of crossover products from the isomerizations of mixtures of (a) allyl-3-13C alcohol and allyl-1,1-d2 alcohol and (b) allyl-1,1-d2 methyl ether and allyl ethyl ether demonstrates that the isomerization of both alcohols and ethers occurs via intermolecular hydrogen shifts. A modified metal hydride addition-elimination mechanism involving exclusive Markovnikov addition to the double bond directed by the oxygen functionality of the substrate has been proposed. © 1994 American Chemical Society.
• France, M. B., Grubbs, R. H., McGrath, D. V., & Paciello, R. A. (1993). Chain transfer during the aqueous ring-opening metathesis polymerization of 7-oxanorbornene derivatives. Macromolecules, 26(18), 4742-4747.
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  Abstract: We have investigated the microstructure of the low molecular weight oligomers using a number of spectroscopic techniques and have identified them as resulting from a true chain transfer mechanism. This is strong evidence for the existence of a ruthenium alkylidene active complex formed from cross-metathesis with an acyclic olefin, which is capable of further productive metathesis.
• McGrath, D. V., Brabson, G. D., Sharpless, K. B., & Andrews, L. (1993). Reinvestigation of the infrared spectra of oxoosmium(VI) esters by isotopic labeling. Inorganic Chemistry, 32(19), 4164-4165.
• Hillmyer, M. A., Lepetit, C., McGrath, D. V., Novak, B. M., & Grubbs, R. H. (1992). Aqueous Ring-Opening Metathesis Polymerization of carboximide-functionalized 7-oxanorbornenes. Macromolecules, 25(13), 3345-3350.
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  Abstract: The ring-opening metathesis polymerization (ROMP) of exo-N-methyl-7-oxabicyclo[2.2.1]-hept-5-ene-2,3-dicarboximide (1) was accomplished in aqueous solution under mild conditions using the simple ruthenium(II) coordination complex RuII(H2O)6(tos)2 (tos = p-toluenesulfonate) (2). The polymerization yield was nearly quantitative. The resultant high molecular weight polymer (poly-1) exhibited a glass transition temperature (Tg) of 225°C and was thermally stable up to 402°C. The thermal and radiative stabilities of poly-1 were further investigated. Poly-1 was hydrogenated to yield its saturated analogue, which had a lower Tg (170°C) but a higher temperature of decomposition (430°C). Complex 2 was deactivated by coordination of free maleimides formed during the polymerization of carboximide-functionalized monomers capable of undergoing retro Diels-Alder chemistry. The scope of this polymerization was therefore limited to carboximide-functionalized monomers that are stable toward retro Diels-Alder reactions at the polymerization temperature. Both ruthenium (II)-1 and ruthenium(II)-N-methylmaleimide olefin complexes were identified. © 1992 American Chemical Society.
• Hillmyer, M. A., Lepetit, C., McGrath, D. V., & Grubbs, R. H. (1991). Aqueous ring-opening metathesis polymerization of exo-N-methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide. American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, 32(1), 162-163.
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  Abstract: The ring-opening metathesis polymerization (ROMP) of strained cyclic olefins is an important application of the olefin metathesis reaction. We have shown that the aqueous ROMP of exo-N-Methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide yields a high molecular weight, thermally stable polymer with a low polydispersity in high yields under mild conditions. The mechanical properties and possible applications of these polymers are currently being investigated.
• McGrath, D. V., Grubbs, R. H., & Ziller, J. W. (1991). Aqueous ruthenium(II) complexes of functionalized olefins: The X-ray structure of Ru(H₂O)₂(η¹(O):η ²(C,C′)-OCOCH₂CH=CHCH₃)₂. Journal of the American Chemical Society, 113(9), 3611-3613.
• Burk, M. J., Crabtree, R. H., & McGrath, D. V. (1986). Identification and determination of millimolar C₆-C₈ alkenes in the corresponding alkanes [4]. Analytical Chemistry, 58(4), 977-978.
• Crabtree, R. H., Dion, R. P., Gibboni, D. J., McGrath, D. V., & Holt, E. M. (1986). C-C bond cleavage in hydrocarbons by iridium complexes. Journal of the American Chemical Society, 108(23), 7222-7227.
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  Abstract: A variety of transformations involving C-C bond cleavage in iridium complexes is described. 1,1-Dimethylcyclopentane reacts with [IrH2(Me2CO)2L2]SbF6 (L = (p-FC6H4)3P, 1) to give first [(5,5-C5H4Me2)IrL2]SbF6 (2) and then [(MeC5H4)IrMeL2]SbF6 (3). The corresponding 5,5-dimethylcyclopentadiene gives 1,2- and 1,3-diethylcyclopentadienyl complexes by a route that involves alkyl migration from ring to metal and back. 4,4-Dimethylcyclopentene also reacts to give 3 but the 3,3-isomer follows a different path to give [(MeC5H4)IrHL2]SbF6. Crystal structures of two diene complexes of type 2 are reported and mechanisms for the reactions observed are proposed. © 1986 American Chemical Society.
• Burk, M. J., Crabtree, R. H., & McGrath, D. V. (1985). Thermal and photochemical catalytic dehydrogenation of alkanes with [IrH₂(CF₃CO₂)(PR₃)₂] (R = C₆H₄F-p and cyclohexyl). Journal of the Chemical Society, Chemical Communications, 1829-1830.
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  Abstract: [IrH2(CF3CO2)(Pcy3) 2] (cy = cyclohexyl) catalyses the photochemical dehydrogenation of cyclo-octane both in the presence and absence of a hydrogen-acceptor.

Proceedings Publications

• Vohnout, S., Rogers, H. R., Plata, R. E., Mcgrath, D. V., & Banister, M. (2007). EAP hydrogels for pulse-actuated cell system (PACS) architectures. In Electroactive Polymer Actuators and Devices (EAPAD) 2007, 6524.
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  Electroactuated polymer (EAP) hydrogels based on JEFFAMINE® T-403 and ethylene glycol glycidyl ether (EGDGE) are used in an infusion pump based on the proprietary Pulse Actuated Cell System (PACS) architecture in development at Medipacs LLC. We report here significant progress in optimizing the formulation of the EAP hydrogels to dramatically increase hydrolytic stability and reproducibility of actuation response. By adjusting the mole fraction of reactive components of the formulation and substituting higher molecular weight monomers, we eliminated a large degree of the hydrolytic instability of the hydrogels, decreased the brittleness of the gel, and increased the equilibrium swelling ratio. The combination of these two modifications to the formulation resulted in hydrogels that exhibited reproducible swelling and deswelling in response to pH for a total period of 10-15 hours.
• Szalai, M. L., & Mcgrath, D. V. (2004, Fall 2004). Vinyl sulfoxide: A versatile trigger for dendrimer disassembly. In 228th ACS National Meeting, Philadelphia, PA.

Poster Presentations

• Huang, Y., Lu, C., Zheng, Y., Jenkins, J. L., Oquendo, L. E., Leight, K. R., Saavedra, S. S., & McGrath, D. V. (2015, MAR 16). Synthesis of Pc-PDI dyads as a molecular heterojunction for studies of electron injection at organic-oxide interfaces. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY.
• Zheng, Y., Giordano, A. J., Cowan, S. R., Fleming, S. R., Shallcross, R. C., Gliboff, M., Huang, Y., Ginger, D. S., McGrath, D. V., Armstrong, N. R., Olson, D. C., Marder, S. R., & Saavedra, S. S. (2014, AUG 10). Surface modification of transparent conducting oxides with functionalized perylene diimide dyes: Characterization of orientation, charge-transfer kinetics, and related OPV performance. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY.
• Hernandez, E., Lu, C., Huang, Y., Lin, H., Oquendo, L., Leight, K., Polaske, N., Armstrong, N., Saavedra, S., & McGrath, D. (2013, April). Molecular Engineering of Donor-Acceptor Dyads for Molecular Heterojunctions on Metal Oxide Surfaces. Arizona Student Energy Conference (AzSEC)University of Arizona.
• Lu, C., Hernandez, E., Huang, Y., Oquendo, L., Collazo-Ramos, A., Leight, K., Lin, H., Saavedra, S., & McGrath, D. (2013, April). Novel Phthalocyanine Architectures for Organic Photovoltaics and Interface Modification. Arizona Student Energy Conference (AzSEC)University of Arizona.
• Muli, D., McGrath, D., Carpenter, B., & Ghiladi, R. (2013, Spring). Synthesis of water-soluble phthalocyanine photosensitizers using click chemistry: Comparison between peripheral and nonperipheral substitution and application in photodynamic therapy. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY. 245th ACS National Meeting, New Orleans, LA.
• Oquendo, L., Lin, H., Ehamparam, R., Polaske, N., Leight, K., Gliboff, M., Knesting, K., Nordlund, D., Ginger, D., Ratcliff, E., Beam, B., Lee, P., Armstrong, N., Saavedra, S., & McGrath, D. (2013, Spring). Modification of indium tin oxide surface with phosphonic acids functionalized asymmetric zinc phthalocyanines. ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY. 245th ACS National Meeting, New Orleans, LA.
• Hernandez, E., Lin, H., Smith, O., Polaske, N., Oquendo, L., Lu, C., Mayukh, M., Green, J., Ratcliff, E., Beam, B., Armstrong, N., Marder SR, ., Saavedra, S., & McGrath, D. (2012, April). Tailor-made NIR absorbing phthalocyanines for organic photovoltaics and interface modification. Arizona Student Energy Conferece (AzSEC)Arizona State University.
• Huang, Y., Lu, C., Lin, H., Hernandez, E., Collazo-Ramos, A., Oquendo, L., Cao, Y., Leight, K., Saavedra, S., & McGrath, D. (2012, October). Investigating Electron and Hole Transfer at Electrode Interfaces: Design and Synthesis of Perylene Diimide-Based Dyads. Interface-to-Face 3 (ITF3). Tucson, AZ.
• Lin, H., Shi, Y., Polaske, N., Oquendo, L., Gliboff, M., Knesting, K., Nordlund, D., Ginger, D., Ratcliff, E., Beam, B., Armstrong, N., McGrath, D., Marder SR, ., & Saavedra, S. (2012, October). Measuring electron transfer rate constants of orientation-controlled phthalocyanine monolayers on ITO by PM-ATR. Interface-to-Face 3 (ITF3). Tucson, AZ.
• Lu, C., Hernandez, E., Yu, C., Mayukh, M., Polaske, N., Chen, X., Pattabiraman, M., Mies, D., Sema, C., Roberts, J., Luscombe, C., Okamoto, K., & McGrath, D. (2012, April). Methods for the Synthesis of Asymmetric Phthalo- and Naphthalocyanine Chromophores: Quest for Functional Tethering and Near-IR Absorption. Arizona Student Energy Conferece (AzSEC)Arizona State University.
• Oquendo, L., Polaske, N., Lin, H., Hernandez, E., Lu, C., Huang, Y., Zheng, Y., Chen, X., Ratcliff, E., Saavedra, S., Armstrong, N., & McGrath, D. (2012, April). Interface Modification of Transparent Conductives Oxides with Tethered Phthalocyanine and Naphthalocyanine Chromophores. Arizona Student Energy Conferece (AzSEC)Arizona State University.