Transient absorption and fluorescence measurements of free radical cation and radical ion pair during pulse radiolysis of 1,3,5-trimethoxybenzene in chlorinated solvents

Transient absorption and laser-induced fluorescence measurements of 1,3,5-t rimethoxybenzene radical cation (TMB.+) during the pulse radiolysis in chlo rinated solvents at room temperature have revealed the formation of an ion pair [TMB.+ Cl-] both through fast and slow processes, electron transfer fr om TMB to chlorine atom and collision between TMB.+ and Cl-, respectively. Fluorescence quantum yield (Phi(f)) measurement has indicated that excited TMB.+ (TMB.+*) in the ion pair undergoes electron transfer quenching by Cl- with a rate constant of 3.0 x 10(11) s(-1) and fluoresces weakly (Phi(f) = 3.1 x 10(-5)) as compared to free TMB.+* (Phi(f) = 1.1 x 10(-3)). (C) 2000 Elsevier Science B.V. All rights reserved.