Viscosity Effects on the Intramolecular Fluorescence Quenching in Dipeptide Model Compounds

Abstract

AbstractThe finding that the increased solvent viscosity decreases the rate for intramolecular fluorescence quenching in the title compounds [N(n)D], giving a singlet‐exciplex intermediate, but increases the rate for the reverse process, regenerating the locally excited singlet‐state N(n)D, is explained in terms of the viscosity‐dependent free‐energy change for this fluorescence quenching process (ΔGet). A linear correlation between the ΔGet and the logarithm of solvent viscosity is found to provide a good criterion for a singlet‐exciplex mechanism in polar solvents.