Reduction of triplet C-60 by hydrogen-bonded naphthols: Concerted electron and proton movement

Hydrogen bonding equilibria, redox potentials and quenching of triplet C-60 in naphthol solutions containing added pyridines are studied by absorption spectroscopy, nanosecond flash photolysis and cyclic-voltammetry. It is shown that the quenching reaction involves reduction of the triplet by a hydrogen bonded naphthol-pyridine pair, with formation of C-60(-)., neutral naphthoxy radical and protonated base. Quenching rates increase with pyridine basicity, in parallel with decreased naphthol oxidation potential, and decrease with deuteration of the naphthol. It is concluded that electron and proton movement from the naphthol respectively to C-3(60) and to base is concerted. Bulk radical yield increases with pyridine basicity and solvent polarity.