Fundamental and second harmonic alternating current cyclic voltamemmeric theory and experimental results for systems in which a first-order chemical reaction follows the charge-transfer step; the EC mechanism

Abstract

A theory-experiment comparison is made for ac cyclic voltammetry with the first-order EC mechanism. Theoretical rate laws are presented and their predictions examined. Experiments used the model electroactive species, cis-Cr(CO) 2(dpm) 2, [dpm bis(diphenylphosphino)mathane]. One-electron oxidation of this molecule at platinum is followed by isomerization of the cis cation to the trans cation. The rate constant for the cis- trans isomerization was measured using the fundamental harmonic reverse/forward peak height ratio, assuming a Nernstian heterogeneous charge-transfer step. Temperatures employed were 261 K (− 12°C), 273 K (0°C), and 293 K(20°C). The isomerization rate constants obtained and the assumption of Nernstian behavior produced good to excellent theory -experiment agreement for the dc, fundamental harmonic ac, and second harmonic ac cyclic voltammograms.