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.