Quenching of Electrogenerated Chemiluminescence by Phenols, Hydroquinones, Catechols, and Benzoquinones

Efficient quenching of Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine) electrogenerated chemiluminescence has been observed in the presence of phenols, catechols, hydroquinones, and benzoquinones. In most instances, quenching is observed with 100-fold excess of quencher over Ru(bpy)(3)(2+), with complete quenching observed between 1000- and 2000-fold excess. The mechanism of quenching is believed to involve energy transfer from the excited-state luminophore to benzoquinone. In the case of phenols, catechols, and hydroquinones, quenching is believed to occur via a benzoquinone derivative formed at the electrode surface. Photoluminescence and UV-visible experiments coupled with bulk electrolysis support the formation of benzoquinone products upon electrochemical oxidation.