ABSTRACT
This chapter describes methods used to generate cations for their photochemical studies, as well as the characterization of their singlet and triplet excited states. Mechanistic studies of excited state carbocations are described, including reactions with nucleophilic species, electron transfer reactions, oxygen quenching, and isomerization processes. Stable organic salts have been used to eliminate the requirement for acidic media and to avoid the problems associated with competitive radical generation that occur via homolytic bond cleavage of carbon-heteroatom bonds in laser flash photolytic experiments. Photooxidation of the triphenylmethyl cation in the presence of an aromatic donor was similarly found to afford bis peroxide. Radical cations may be photochemically generated through photoinduced electron transfer, photoionization, or electron transfer to a photolytically generated oxidant. Photochemically generated radicals undergo a subsequent photoinduced or thermal oxidation to the corresponding carbocation.
