Phenol substituent effects on electrogenerated chemiluminescence quenching

Efficient quenching of Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine) electrogenerated chemiluminescence (ECL) was observed in the presence of phenol and substituted phenols (e.g., 4-fluorophenol). Spectroscopic and electrochemical studies indicated that the mechanism of quenching involves energy transfer from the excited state luminophore to a benzoquinone derivative formed at the electrode. The efficiency of ECL quenching is directly related to the position of the substituent on the aromatic ring, with meta derivatives displaying the greatest magnitude of quenching. The degree of quenching does not appear to be related to the electron-donating or -withdrawing ability of the phenol substituent.