Triplet lifetime of chlorotoluenes in the vapor phase studied by time-resolved and stationary photosensitized phosphorescence

Abstract

Abstract Time-resolved observation of biacetyl phosphorescence sensitized by p -chlorotoluene vapor has led to rate constants of non-radiative decay ( k nr and energy transfer to biacetyl ( k ET ) from the lowest triplet state of p -chlorotoluene in the vapor phase. The decay rate constant of thermalized triplet p -chlorotoluene is 2.5×10 5 s −1 , about two orders of magnitude faster than that of toluene. The energy transfer rate constant to biacetyl is 2.9×10 10 M −1 s −1 similar to that of toluene. Stationary measurements of the phosphorescence intensity of biacetyl sensitized by p -chlorotoluene vapor led to a value of k nr / k ET of 8.6×10 −6 M, which is in close agreement with that (8.8×10 −6 M) obtained by time-resolved observation. Non-radiative decay and energy transfer rate constants for o - and m -chlorotoluenes in the lowest triplet state were also obtained.