The structure of low-temperature electronic spectra of benzo[a]phenazine

Abstract

A vibrational analysis of the multi-site phosphorescence spectra of benzo[a]phenazine (BPH) in n-hexane and of the single-site phosphorescence spectra obtained by direct T 1(π,π*)/alS o laser excitation in a glassy medium furnished consistent results. Using polarization spectra, the symmetries of fundamentals active in the phosphorescence spectra have been assigned. The BPH molecule occupies in a n-hexane matrix three main sites. The site splitting is much larger in the T 1 than in the S 1 state. The energy gap between the S 2(ππ*) and the S 1(nπ*) state is only 650 cm −1. In the interference region between these two slates large intensity differences in the phosphorescence excitation spectra of the individual sites are observed.