Quenching of electrogenerated chemiluminescence by phenols, hydroquinones,catechols, and benzoquinones

Efficient quenching of RU(bpy)(3)(2+) (bpy = 2,2'-bipyridine) electrogenera ted chemiluminescence has been observed in the presence of phenols, catecho ls, hydroquinones, and benzoquinones. In most instances, quenching is obser ved with 100-fold excess of quencher over Ru(bpy)(3)(2+), with complete que nching observed between 1000- and 2000-fold excess. The mechanism of quench ing is believed to involve energy transfer from the excited-state luminopho re to benzoquinone. In the case of phenols, catechols, and hydroquinones, q uenching is believed to occur via a benzoquinone derivative formed at the e lectrode surface. Photoluminescence and UV-visible experiments coupled with bulk electrolysis support the formation of benzoquinone products upon elec trochemical oxidation.