Cyclic voltammetric studies of some tris(diimine)cobalt(n) complexes in dimethylformamide solution

Department of Chemistry, University of Allahabad, Allahabad-211 002, Uttar Pradesh, India E-mail: dr_krishna_s@yahoo.co.in Manuscript received 7 December 2006, revised 6 February 2007, accepted 8 February 2007 The cyclic voltammetric behaviour of tris(diimine)cobalt(II) complexes, [CoL3]2+, (L = diimine = bipyridyl (bipy), phcnanthroline (phen) and 4,7-diphenyl-1,10-phenanthroline (bathophen)) has been investigated in DMF solution containing 0.1 M NaCIO4 as a supporting electrolyte at a glassy carbon working clectrodl' (GCE). All these complexes undergo a diffusion-controlled quasi-reversible one- electron oxidation couple (Co2+/3+) at Eo'= +320 to +430 mV vs SCE and a single-electron reduction couple (Co2+/+) at Eo' = -680 to -690 mV vs SCE. The peak current ratio for both oxidation and reduction couples is less than unity, suggesting that redox proces~es involve EC mechanism. CV results also revealed that the ease of reduction increases in the order : hipy→phen →bathophen, clearly demonstrating that the chemical nature, size and positions oft he substituents on the parent phenanthroline rings, i.e., the electronic and steric characteristics of the ligands influence the redox potentials of the complexes