Excited state dynamics of p-chlorotoluene in rigid glass matrices

Abstract

Excited state dynamics of dual phosphorescent p-chlorotoluene (PCT) was investigated in 3-methylpentane (3MP), methylcyclohexane (MCH), ethanol/methanol (EtOH/MeOH) and EPA rigid matrices in the temperature range of 77-110 K. Dual phosphorescence was ascribed to two low-lying triplet states, 3 ππ * and 3 πσ *. The rate of intersystem crossing (ISC) from S 1 to 3 ππ * and 3 πσ * states depends both on the temperature and solvent. Mutual conversion process between 3 ππ * and 3 πσ * states was observed above 87 K in 3MP, 92 K in MCH and 105 K in EtOH/MeOH matrices. Non-radiative decay rate constants strongly depend on the viscosity of the solvent; in the more viscous solvent, non-radiative decay rates become smaller. The activation energies depend on the solvent viscosity and it was ascertained that the mutual conversion process between 3 ππ * and 3 πσ * requires conformational change.