Phosphorescence Spectra and Excited States Dynamics of Chlorotoluenes in a Rigid Glass Matrix

Abstract

Abstract The excited-state dynamics of chlorobenzene (CB), o-chlorotoluene (o-CT), m-chlorotoluene (m-CT) and p-chlorotoluene (p-CT) have been investigated in 3-methylpentane at 77 K. The phosphorescence spectra of CB and o-CT show a maximum at around 510 nm, while the maxima of m-CT and p-CT are 450 and 420 nm, respectively. These phosphorescence spectra are divided into dual phosphorescence spectra: namely 3ππ* and 3πσ* phosphorescence. The large phosphorescence peak-shifts among the chlorotoluenes are ascribable to a lowering of the low-lying 3ππ* state. The intersystem-crossing (ISC) quantum yields from S1 to 3ππ* (φISCππ*) depend on the samples, whereas φISCπσ* from S1 to 3πσ* are independent of the sample. These results have been explained in terms of the vibrational Franck-Condon overlap between the S1 state and triplet manifolds.