ADMITTANCE MEASUREMENTS OF ADSORPTION PROPERTIES OF 2,2'-BIPYRIDINE COMPLEXES .1. COBALT(II) AND NICKEL(II) COMPLEXES IN AQUEOUS-SOLUTIONS

The complex [Co bipy3]2+ in aqueous perchlorate solution yields on the d.c. polarogramthree adsorption type pre-waves and a main reduction wave at -1.2 V (SCE) corresponding to the reduction to monovalent complex. From admittance measurements and other results it can be concluded that two most positive pre-waves at -0.2 V and -0.5 V (SCE) are of non-faradaic nature being related to the adsorption of the complex with specifically adsorbed anions of the supporting electrolyte with the formation of a compact adsorbed layer of much lower interfacial capacity. The most negative pre-wave at -0.9 V just preceding the main wave corresponds to the reduction of the adsorbed complex. The main wave at -1.2 V is distorted by the adsorption of reaction products. Very similar and also strong adsorption-coupled interaction was found with divalent nickel trisbipyridine complex. © 1979 Elsevier Sequoia S.A.