Dominic V Mcgrath

Professor, Chemistry and Biochemistry-Sci

Professor, BIO5 Institute

Primary Department

Chemistry & Biochemistry

Department Affiliations

Chemistry & Biochemistry

BIO5 Institute

Contact

(520) 626-4690

mcgrath@u.arizona.edu

Research Interest

Dominic Mcgrath, PhD, set forth a program which involves the use of organic synthesis for the design, development, and application of new concepts in macromolecular, supramolecular, and materials chemistry. Research efforts span a number of areas in the chemical sciences and include studies of: 1) chiral dendritic macromolecules and the effect of chiral subunits on dendrimer conformation, 2) photochromic dendrimers and linear polymers which undergo structural changes in response to visible light, 3) liquid crystalline materials based on dendritic and photochromic mesogens, and 4) synthesis of new ligands based on saturated nitrogen heterocycles.A continuing interest remains in the effect of structural perturbations on the properties and functional of dendritic macromolecules. Part of this research addresses the design, synthesis, and study of dendrimeric materials containing chiral moieties in the interior for influencing the conformational order of these 3-dimensional macromolecules. An ultimate goal is to develop materials active for the selective clathration of small guest molecules. Potential applications include chemical separations, sensor technology, environmental remediation, and asymmetric catalysis.Dr. Mcgrath and his lab team recently developed several new classes of dendritic materials containing photochromic subunits. As nature uses light energy to alter function in photoresponsive systems such as photosynthesis, vision, phototropism, and phototaxis, they use light energy to drive gross topological or constitutional changes in fundamentally new dendritic architectures with precisely placed photoresponsive subunits. In short, they can drive dendrimer properties with light stimuli. Two entirely new classes of photoresponsive dendritic macromolecules have been developed and include: 1) photochromic dendrimers and 2) photolabile dendrimers. Dr. Mcgrath anticipates that switchable and degradable dendrimers of this type will have application in small molecule transport systems based on their ability to reversibly encapsulate guest molecules. He continues to develop these materials as potential transport hosts and photoresponsive supramolecular assemblies.

Publications

Solvent-free synthesis of soluble, near-IR absorbing titanyl phthalocyanine derivatives

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

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.

Effect of covalently incorporated azobenzenes on dendrimers

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.

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.

Electron Transfer Processes in Zinc Phthalocyanine-Phosphonic Acid Monolayers on ITO: Characterization of Orientation and Charge Transfer Kinetics By Waveguide Spectroelectrochemistry

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

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.

Synthesis of amphiphilic photoresponsive dendrons

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.

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.

Asymmetric ZnPc-TEG photosensitizers: the effect of Pc substitution on phototoxicity

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

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.

Dominic V Mcgrath