Understanding the structural and environmental factors that control the excited-state homolytic and heterolytic bond scission is the key for improved applications in photo-catalysis, photo-switching and photo-initiation processes. In this work, we explore the structure-property relationship of a model heterolytic process: namely the photochemical release of hydroxide and other anions from acridinol and xanthenol-based model compounds (photobases). The thermodynamic force for the excited-state anion release was tuned using the substituent effects in a series of photobase derivatives. Then, ultrafast time-resolved laser spectroscopy was utilized to determine the kinetics of the photo-heterolysis in a series of solvents with different polarity. The rate dependence on the thermodynamic driving force was modeled to evaluate the intrinsic activation barriers for excited-state OH- ion release and the results were compared to those observed by us and others in photoacids. The results show that the excited-state OH- release is feasible, but slower than the H+ release. The results are discussed in terms of the differences in the structures of solvated proton and hydroxide ion.

Photobases: Excited-state C-O bond heterolysis in protic solvents

256th National Meeting (2018)

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