Phosphorescence of substituted benzenes and their lowest triplet states

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Abstract
The energies of the lowest triplet states of several substituted benzenes were experimentally determined by measuring the phosphorescence spectra at 77°k. The compounds studied here are phenol, anisole, aniline, N,N-dimethylaniline, p-phenylenediamine and N,N,N′,N′-tetramethyl-p-phenylenediamine. Theoretical studies of π-electronic structures of triplet states of these substituted benzenes were carried out by considering configurational interactions between the locally excited triplet configurations of benzene and the intramolecular charge-transfer triplet configurations. Good agreement was obtained between the experimental and theoretical values for energies of the lowest triplet states. The amounts of contributions from the original electronic configurations to the resulting lowest triplet states of these substituted benzenes were evaluated from the calculated wave functions. The chemical properties of the phosphorescent states are discussed in terms of the intramolecular charge-transfer contributions.