Prof. D.L. Phillips　　　裴達偉教授

B.Sc. Iowa State;
Ph.D. California

Phillips Research Group Webpage

Room 401
Chong Yuet Ming Chemistry Building
The University of Hong Kong
Pokfulam Road
Hong Kong

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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.

Photodissociation, Photoisomerization and Photocyclopropanation Reactions of Polyhaloalkanes

Polyhalomethanes like CFCl₃, CCl₄, CHBr₃, CHBr₂Cl, CH₂I₂, CH₂Br₂ and CH₂BrI have been observed in the atmosphere and are important sources of reactive halogen species in the atmosphere. Polyhalomethanes are also of interest in synthetic chemistry for cyclopropanation reactions. We have recently shown that ultraviolet photolysis of polyhalomethanes in room temperature solutions leads to appreciable formation of novel iso-polyhalomethane photoproduct species. The iso-diiodomethane species can act as the methylene transfer agent in photo-cyclopropanation reactions using photolysis of diiodomethane in the presence of olefins. We are using resonance Raman and time-resolved resonance Raman spectroscopy as well as density functional theory calculations to better understand the iso-polyhalomethane species and its chemical reactivity.

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/chemistry of a number of compounds in the natural environment and in the design of efficient photocatalysts/catalysts for degradation of pollutants in water.

Structure, Properties and Chemical Reactions of Arylnitrenium Ions and Selected Phototrigger Compounds

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 metabolism 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.

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.

1. K.H. Leung, D.L. Phillips, M.C. Tse, C.M. Che, V.M. Miskowksi, J. Am. Chem. Soc., 1999, 121, 4799-4803.
2. X. Zheng, D.L. Phillips, J. Phys. Chem. A, 2000, 104, 6880-6886.
3. Y.L. Li, K.H. Leung, D.L. Phillips, J. Phys. Chem. A, 2001, 105, 10621-10625.
4. D.L. Phillips, W.H. Fang, X. Zheng, J. Am. Chem. Soc., 2001, 123, 4197-4203.
5. P. Zhu, S.Y. Ong, P.Y. Chan, K.H. Leung, D.L. Phillips, J. Am. Chem. Soc., 2001, 123, 2645-2649.
6. P. Zhu, S.Y. Ong, P.Y. Chan, Y.F. Poon, K.H. Leung, D.L. Phillips, Chem. Eur. J., 2001, 7, 4928-4936.
7. C. Zhao, D. Wang, D.L. Phillips, J. Am. Chem. Soc., 2002, 124, 12903-12914.
8. C. Zhao, D. Wang, D.L. Phillips, J. Am. Chem. Soc., 2003, 125, 15200-15209.
9. W.M. Kwok, C. Zhao, Y.L. Li, X. Guan, D. Wang, D.L. Phillips, J. Am. Chem. Soc., 2004, 126, 3119-3131.
10. C. Ma, W.M. Kwok, W.S. Chan, P. Zuo, J.T.W. Kan, P.H. Toy, D.L. Phillips, J. Am. Chem. Soc., in press.