The effect of heterocyclic S,S’-ligands on the electrochemical properties of some cobalt(III) complexes in acid

• Main Authors: Jovanović Vladislava M., Babić-Samardžija K., Sovilj Sofija P.
• Format: Article
• Language: English
• Published: Serbian Chemical Society 2005-01-01
• Series: Journal of the Serbian Chemical Society
• Subjects: cobalt(iii) complexes; azamacrocycles and dithiocarbamate; cyclic voltammeter; glassy carbon; iron; perchloric acid
• Online Access: http://www.doiserbia.nb.rs/img/doi/0352-5139/2005/0352-51390501051J.pdf
• ISSN: 0352-5139; 1820-7421

Eight mixed-ligand cobalt(III) complexes with the macrocyclic amine 1,4,8,11-tetraazacyclotetradecane (cyclam) and a heterocyclic dithiocarbamate (Rdtc-)i.e., morpholine-(Morphdtc), thiomorpholine- (Timdtc), piperazine-(Pzdtc), N-methylpiperazine-(Mepzdtc), piperidine- (Pipdtc), 2-, 3- or 4-methylpiperidine-(2-, 3- and 4-Mepipdtc) carbodithionato-S,S ions, of the general formula [Co(cyclam)Rdtc](ClO4)2, were investigated in deoxygenated 0.1 MHClO4 solutions. Cyclic voltammetry data at a glassy carbon (GC) electrode demonstrate a redox reaction of cobalt(III) from the complexes at potentials strongly influenced by the presence of different heterocyclic Rdtc- ligands. In this respect, the complexes were separated into two groups: the first, with a heteroatom O, S or N in the heterocyclic ring, and the second, with a methyl group on the piperidine ring of the Rdtc- ligand. Anodic polarization of an Fe electrode in the presence of the complexes shows their influence not only on the dissolution of iron but also on the hydrogen evolution reactions and on this basis complexes the complexes could be divided into the same two groups. It was found that the weaker the inhibiting effect of the free heterocyclic amines is, the significantly higher is the efficiency of the corresponding complexes.