Solvent effects on rates of photochemical reactions of rose bengal triplet state studied by nanosecond laser photolysis

摘要: Abstract Bimolecular rate constants of energy transfer, electron-transfer, and H-atom abstraction reaction have been determined by following the transient absorption bands triplet states rose bengal [ 3 ( RB 2− ) ∗ ] at about 1020 nm with various substrates using nanosecond laser flash photolysis. For electron acceptor (1,4-benzoquinone), electron-transfer takes place via an exciplex. Exciplex formation was found to be predominant in high viscosity solvents rather than low solvents. donor (3,3′,5,5′-tetramethylbenzidine), are independent solvent viscosity, indicating that contribution exciplex is small. The reactions H-donors show water higher those ethanol THF. negative slopes Hammett plots indicate center has a highly electrophilic nature, which increases polarity, suggesting polar transition states.