The formation of singlet and triplet charge transfer states on photo-excitation of carbazole-(CH 2) n-tetrachlorophthalimide compounds studied by time-resolved microwave conductivity

Abstract

The formation and decay of charge transfer (CT) states resulting from photo-induced intramolecular electron transfer from carbazole to tetrachlorophthalimide joined by di-, tri-, tetra-, and hepta-methylene spacers has been studied by the time-resolved microwave conductivity (TRMC) technique in the solvents cyclohexane, trans-decalin, benzene, and para-dioxane. Both short-lived, singlet, and long-lived, triplet, CT states are observed. The triplet CT state can be formed by intersystem crossing from the singlet CT state subsequent to electron transfer, as is the case for the three shortest bridge compounds, and also via formation of the local acceptor triplet state prior to electron transfer, in the case of the hepta-methylene compound.