Viscosity Effect Study on Quenching of Photoinduced Excited Triplet Duroquinone by TEMPO

Abstract

ABSTRACT Quenching dynamics of excited quinone molecules are given much attention in photochemistry and biochemistry. In order to study the viscosity effect on the quenching of triplet excited state of duroquinone (3DQ*) by stable radical, 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO), this study measured chemically induced dynamic electron polarization (CIDEP) spectra and transient absorptive spectra in various solvents. The solvents used were ethylene glycol, 1,2-propanol and their mixtures with different ratio in volume. The Stern-Volmer plot was obtained form CIDEP spectra of photolysis of DQ with different TEMPO concentrations. Combining the slope of the Stern-Volmer plot with lifetime of 3DQ*, determined from the 3DQ* transient absorbance decay curve, the quenching rate constants of 3DQ* by TEMPO were calculated in each solvent. The results indicate that the quenching rate constant is viscosity-dependent, and that it decreases linearly with the increase in solvent viscosity in the range used in our experiment.