Phenol substituent effects on electrogenerated chemiluminescence quenching

Efficient quenching of Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine) electrogenera ted chemiluminescence (ECL) was observed in the presence of phenol and subs tituted phenols (e.g., 4-fluorophenol). Spectroscopic and electrochemical s tudies indicated that the mechanism of quenching involves energy transfer f rom the excited state luminophore to a benzoquinone derivative formed at th e electrode. The efficiency of ECL quenching is directly related to the pos ition of the substituent on the aromatic ring, with meta derivatives displa ying the greatest magnitude of quenching. The degree of quenching does not appear to be related to the electron-donating or -withdrawing ability of th e phenol substituent.