<p> This thesis describes a study of the photosolvolysis of N-benzoyl-5-bromo-7-nitroindoline. The investigation was instigated because N-acyl-5-bromo-7-nitroindolines have been considered as potential photoprotecting groups for the photolithographic formation of charge-mosaic membranes. However, no kinetic data, and only scant mechanistic information, has been reported for the photofragmentation process.</p> <p> Both absorption and emission spectra of N-benzoyl-5-bromo-7-nitroindoline were obtained. Based on the electronic spectra, it would seem that the two lowest energy singlet excited states are nearly isoenergetic and their relative energies are a function of the solvent medium.</p> <p> The distribution of photoproducts obtained from irradiation of N-benzoyl-5-bromo-7-nitroindoline in various solvent systems was investigated. It was shown that the photosolvolysis reaction is a function of the solvent properties. Thus 5-bromo-7-nitroindoline and benzoic acid were the only photoproducts formed in acetonitrile. In acetonitrile-water, 5-bromo-7-nitrosoindole as well as 5-bromo-7-nitroindoline and benzoic acid were identified. A correlation between solvent polarity, ET(30), and 5-bromo-7-nitrosoindole formation was observed.</p> <p> The mechanism of the fragmentation mode was examined. The presence of a free radical intermediate is suggested from the photoproduct distribution in tetrahydrofuran (THF). Observation of an electron spin resonance (e.s.r.) spectrum during irradiation of N-benzoyl-5-bromo-7-nitroindoline in an e.s.r. spectrometer cavity, 18_0 incorporation into benzoic acid, and a linear free energy relationship with sigma dot (σ•) corroborated the intermediacy of a free radical in the fragmentation process.</p> <p> Quantum yields of N-benzoyl-5-bromo-7-nitroindoline disappearance in different solvents and quenchers were measured in order to establish the reactive excited state and the effect of the medium on the efficiency of the transformation process. A solvent dependency on both the excited state lifetime and photosolvolysis reaction efficiency was noted. The results were indicative of a change in mechanism with a variation in solvent polarity and/or hydrogen bonding ability.</p> <p> A mechanism compatible with experimental results and applicable to previously reported N-acyl-2-nitroaniline photofragmentations is proposed.</p> / Thesis / Doctor of Philosophy (PhD)

This Thesis aims to examine the effects of substituents on the adjacent proton accepting phenyl ring with respect to a new type of excited state intramolecular proton transfer (ESIPT) process discovered by Wan and co-workers. Therefore, a number of 2-phenylphenols 23-28 were synthesized with electron-donor and electron-acceptor substituents such as methyl, methoxy, and ketone moieties on the adjacent proton accepting phenyl ring. The results obtained from examination of photochemical deuterium exchange showed that all derivatives except for ketone 27 underwent deuterium exchange (Фex = 0.019 - 0.079), primarily at the 2’-position on photolysis in D2O-CH3CN. In general, compounds with methoxy moiety (ies) on the adjacent proton accepting ring showed higher deuterium exchange yields. Diol 28 has the potential to undergo photosolvolysis as well as ESIPT process since it has both a benzyl alcohol and a phenol chromophore on the same molecule. Irradiation of 28 in 1:1 H2O-CH3OH gave the corresponding methyl ether product in high yield. Photolysis of 28 in 1:1 D2O-CH3OH also showed that ESIPT competes very well with photosolvolysis. Thus, this work has established that ESIPT can compete efficiently with photosolvolysis. Semi-empirical AM1 (examination of HOMOs and LUMOs) calculations show a large degree of charge transfer in the electronic excited state (except 27), from the phenol ring to the attached phenyl ring of the studied compounds. The AM1 calculation for ketone 27 showed that the carbonyl oxygen is more basic than the carbon atoms of the benzene ring, which explains the lack of deuterium exchange observed for 27.