Electron Transfer on the Photodehalogenation of 2-(4-chlorophenyl)benzoxazole Assisted by Amines

Article abstract of DOI:10.1021/jo00391a039

The photochemical reactivity of 2-(4-chlorophenyl)benzoxazole in the presence of a series of amines has been investigated.A fluorescence quenching study provides evidence for the formation of an exciplex between the singlet excited state of the benzoxazole derivative and the amine in its ground state.This exciplex gives rise to a charge-transfer complex (CTC).The quenching fluorescence date can be fitted by a Weller-Marcus system, thus leading to large reorganization energies.The measurment of dehalogenation, which is drastically increased in the presence of amines, allowed us to estimate the reactivity of the CTC.In the case of tertiary amines, 1percent of the CTC formed via the singlet state leads to the dehalogenation.For secondary amines a hydrogen transfer between the amine and the excited triplet state of the chloro compound is also postulated.