Electrochemiluminescence of Osmium Complexes: Spectral, Electrochemical, and Mechanistic Studies

Electrochemical, spectral, and electrochemiluminescent (ECL) studies of bipyridine and phenanthroline complexes of osmium are presented. ECL was observed for a large number of complexes, but the emission intensity in some cases proved to be much lower than anticipated. For , this was determined to be due to an EC process taking place after oxidation of the complex to give rise to . Surface ECL was demonstrated for electropolymerized films of (dstyr‐bpy is 4,4' distyryl 2,2' bipyridine). The phenomenon of intramolecular ECL was probed by studies on (Fc‐p is 1,1' bis diphenyl phosphino ferrocene). It was found that instead of intramolecular ECL being operative, a quenching mechanism was responsible for the observed behavior. For complexes that do not exhibit complications, there was a linear correlation between the solution luminescence quantum yield and the ECL emission intensity, consistent with the direct formation of the excited state via the redox process without any intervening steps or additional relaxation pathways.