Electrogenerated chemiluminescence. 65. An investigation of the oxidation of oxalate by tris(polypyridine) ruthenium complexes and the effect of the electrochemical steps on the emission intensity

The homogeneous oxidation of oxalate has been investigated at an ultramicro electrode by means of redox catalysis with different iron and ruthenium coo rdination complexes. Kinetically, the process is governed by the first elec tron transfer. It can be rationalized by Marcus theory. When the electron a cceptor is a ruthenium coordination complex, the second electron transfer c an generate a luminescent excited state of the ruthenium. This electrochemi luminescent process is related, in a first approximation, to the catalytic efficiency of the homogeneous oxalate oxidation, but also to the different competing routes for the second electron transfer (oxidation of CO2.-). The effect of the pH and the ionic strength on the redox catalysis and the lig ht emission are discussed.