Research

Time-Resolved Spectroscopy, Reactive Intermediates, Reaction Mechanisms and Vibrational Characterization of Molecular Excited States and Chemical Reactions

PHOTOCHEMISTRY, CHEMICAL DYNAMICS AND MOLECULAR SPECTROSCOPY

Molecular electronic excited states usually exhibit chemical reactivity and structures very different from those of the corresponding ground electronic state of the molecule. Some examples of processes that make use of molecular excited states are photosynthesis, photocatalysis, photodynamic therapy treatments of tumors and other reactions. The goal of the following research projects is to better understand the structure and dynamics of short-lived molecular species and better understand chemical reaction mechanisms

1. Water Catalyzed Dehalogenation Reactions of Selected Halogenated Molecules

We have recently elucidated how water assists several different types of dehalogenation reactions leading to formation of strong acid leaving groups and facile cleavage of C-H, O-H and C-X bonds. This project seeks to use a combination of experimental and theoretical studies to better understand how water is able to catalyze or assist these types of chemical reactions. This work has important implications for the phase dependent photochemistry of a number of compounds in the natural environment and in the design of efficient photocatalysts for degradation of pollutants in water.

2. Structure, Properties and Chemical Reactions of Arylnitrenium Ions

Carcinogenic aromatic amines are found in automobile fumes, tobacco smoke, broiled or fermented meat and as unwanted trace products in industrial processes. These carcinogenic compounds typically transfer an arylamine to DNA which then undergoes a chemical reaction that damages the DNA. Nitrenium ions have been found to play an important role in the metaobolism reactions of carcinogenic arylamines that damage DNA. It is important to understand the structures and reactivities of these short-lived nitrenium ions and their reaction intermediates. We are using time-resolved resonance Raman spectroscopy experiments to obtain missing structural information for selected nitrenium ions and their reaction intermediates.

3. Structure, Properties and Chemical Reactions of Phototrigger Compounds

Phototrigger compounds are used to release biological active species for use in physiology experiments. Several new classes of phototrigger compounds have been developed but the reaction mechanism(s) for how the photoremovable group is released remains unclear. Experimental and theoretical work is on-going to better characterize and identify the chemical reaction intermediates and to elucidate the reaction mechanism(s) involved in the release of the photoremovable group from these phototrigger compounds.

4. Structure, Properties and Chemical Reactions of Benzophenone Containing Drugs

Many benzophenone-derived drugs suffer from photosensitization reactions that lead to unwanted phototoxic effects but have useful applications as non-steroidal anti-inflammatory agents and as other therapeutic agents. To best utilize these types of benzophenone drugs and to design and develop improved benzophenone derived drugs with lower phototoxicity, it is important to clearly identify the reaction intermediates and understand the reaction mechanism(s). We will use time-resolved resonance Raman spectroscopy to investigate the reactions of selected benzophenone-derived photosensitizing drugs to supply this missing structural information.