Solvent Effect in the electron transfer quenching of the triplet state of anthracene by p-benzoquinones.

GRACIELA P. ZANINI; HERNÁN MONTEJANO

BOLETíN DE LA SOCIEDAD CHILENA DE QUíMICA

Sociedad Chilena de Química

Lugar: Concepcion, Chile; Año: 2001 vol. 46 p. 81 - 90

0366-1644

Here we present an investigation of the quenching of anthracene triplet by several p-benzoquinones, in two solvents of nearly equal macroscopic dielectric properties, methanol and acetonitrile. Bimolecular quenching rate constants were measured by laser flash photolysis. Quantum efficiencies of charge separation were also determined in the protic solvent. Quenching rate constants in acetonitrile follow a typical Rehm-Weller correlation for an electron transfer process. Although free radical ions are observed in methanol, the rate constants are nearly independent on the driving force, at variance of the expected behavior. In this solvent, the charge separation quantum yield decreases when the energy of the ion-pair decreases, in agreement with the energy gap law