SOLVENT INFLUENCES ON THE SINGLET QUENCHING OF CHLOROPHYLLaBY 2, 5‐DIMETHYL‐p‐BENZOQUINONE

Abstract
Abstract—The quenching of chlorophyllaexcited singlet states by 2.5‐dimethyl‐p‐benzoquinone has been investigated in solvents of varying viscosity and polarity. The observed singlet lifetimes showed little variation in several hydrocarbon solvents. Stern‐Volmer constantKdepends on the viscosity of the solvent, although cyclic and straight‐chain hydrocarbons behave somewhat differently. The decrease of theKvalues with increase of viscosity suggests that the quenching mechanism is at least partly dynamic, although there is evidence for static quenching as well. The influence of solvent polarity on theKvalues was found to be insignificant, which is consistent with a very short‐lived ion pair intermediate formed by electron‐transfer quenching.

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