Dynamic Solvent Effects in Thermal Fading of a Merocyanine Formed from a Spironaphthopyran

Abstract

Pressure and viscosity effects on a thermal fading of a merocyanine formed from a spironaphthopyran were studied in nonviscous and viscous solvents. The activation volume was positive in all of the solvents studied, however, the reaction was retarded more strongly in viscous solvents and the magnitude of this effect increased with increasing pressure. Temperature dependence of the rate constant at a constant viscosity clearly indicated that solvent and chemical structural changes have to be treated by two mutually independent reaction coordinates as proposed by Agmon and Hopfiled.