Mechanistic Studies on the Dual Reaction Pathways of Singlet Excited Dibenzoyl(methanato)boron Difluoride (DBMBF2): Reactions of the Excimer and Exciplexes

Abstract

The mechanism of the interaction of singlet excited dibenzoyl(methanato)boron difluoride (*DBMBF2 = *A) with olefins and substituted benzenes (SB) was investigated by the determination of effective quenching distances (Reff) from fluorescence monitors in acetonitrile as analyzed by the Smoluchowski−Collins−Kimball equation and by solvent effects on the dichotomy of the formation of cycloadducts and [4 + 2] dimers from 1,3-cyclohexadiene (CHD) and 1,3-cyclooctadiene (1,3-COD). The correlation of Reff with directly demonstrates that the reactants have to get closer to affect electron transfer from these substrates as the driving force become more positive and coalesce on exciplexes. Both photophysical and photochemical probes converge on the partition of encounter pairs to the SSRIP (the ket pathway which leads to radical ion reactions and nonfluorescent) and exciplexes (the kex pathway which leads to cycloadducts and fluorescent species); the former pathway was promoted by low redox energies of donor−accep...