Electron transfer reactions in metal ammine complexes—IV: Reduction of some amino acid, aminobenzoic acid and their Schiff base substituted pentaammine Cr(III) complexes at the dropping mercury electrode

Abstract

Aminoacid, aminobenzoic acid and their Schiff base substituted pentaammine Cr(III) perchlorate complexes undergo an irreversible, one electron reduction process at the dropping mercury electrode. The rates of the electrode process k app, calculated from the values of diffusion current at the end of the life of the mercury drop, show small enhancements in presence of iodide ions. On comparing these rate enhancement values with the corresponding value for the reduction of [Cr(NH 3) 6] 3+, which undergoes a completely outer-sphere path, it is concluded that these complexes follow a mixed inner/outer-sphere path. The contribution of the inner-sphere path is maximum in the case of aminoacid complexes and minimum in the case of Schiff bases of aminobenzoic acids. These results are further supported by the values of α app, obtained from Tafel plots and other electrical double layer parameters like ( δΦ r / δE) μ , ( δδ r / δq m ) μ and α corr.