Time-Resolved Spectroscopic Studies of Selected Photoredox and Photodeprotection Reactions of Aromatic Carbonyl Compounds in Aqueous Solutions

Professor Phillips, David Lee   (Principal Investigator (PI))

Professor Li Mingde   (Co-Investigator)

36

2015-07-01

706972

Time-Resolved Spectroscopic Studies of Selected Photoredox and Photodeprotection Reactions of Aromatic Carbonyl Compounds in Aqueous Solutions

aromatic carbonyls, excited states, reaction mechanism, reactive intermediates, time-resolved spectroscopy

Chemical Sciences

Physical Sciences (P)

17301815

General Research Fund (GRF)

2015

Completed

1 Time-resolved absorption (fs-TA and ns-TA) and TR3 spectroscopy experiments will be performed to investigate the photoredox and/or photodeprotection reactions of derivatives of selected benzophenone (BP) and anthraquinone (AQ) compounds so as to characterize the excited states and reactive intermediates and reaction mechanisms for the compounds of interest. 2 Time-resolved absorption (fs-TA and ns-TA) and TR3 spectroscopy experiments will be done to investigate how the substituent and leaving group properties influence the deprotection reactions of ketoprofen (KP) based phototrigger compounds in aqueous solutions of varying pH. This will help better understand how substituents with varying properties and located at different positions will affect the behavior and outcome for the photodeprotection reactions of interest. 3 Time-resolved absorption (fs-TA and ns-TA) and TR3 spectroscopy experiments will be performed to investigate benzophenone alcohols like 2-(3’-benzoyl)phenethyl alcohol that undergo a base catalyzed elimination of formaldehyde and form a 3-methylbenzophenone side product. Experiments will also be done in aqueous solutions of varying pH values in order to better understand why this reaction only appears to be appreciable in strongly basic and acidic solutions but only trace amounts of the reaction were observed in neutral and slightly basic aqueous solutions. 4 Time-resolved absorption (fs-TA and ns-TA) and TR3 spectroscopy experiments will be done to study photoenolization based photorelease reactions for selected ortho-alkyl substituted aromatic carbonyl compounds that have a good leaving group on the ortho-alkyl substituent or the -position next to the aromatic carbonyl in aqueous solutions of varying pH values. This work aims to develop an improved understanding of the reaction mechanisms, and what role the water and pH conditions play in the photoenolization reactions and the release mechanism(s) of interest. 5 Time-resolved absorption (fs-TA and ns-TA) and TR3 spectroscopy experiments will be performed to examine photoenolization based photorelease reactions for selected ortho-alkyl substituted aromatic carbonyl compounds in which the cleavage of the leaving group occurs by intramolecular relactonization of the photoenol alcohol group with an ester moiety. This work will help gain a better understanding of the reaction mechanisms and the role water and pH conditions play in the photoenolization and intramolecular relactonization of the photoenol alcohol group with an ester moiety. 6 The accumulated experimental and computational results gained in objectives 1-5 will be compared to each other in order to help determine similarities and differences in their excited states, intermediates, substituent effects and pH dependence for their associated photochemistry. This may be helpful to determine promising trends and/or properties that may be useful to explore in the design of improved photoredox and photodeprotection compounds for use in particular applications with certain aqueous pH conditions.