J. Indian Chern. Soc., Vol. 84, December 2007, pp. 1195-1198 Effect of solvents on the electrochemical behaviour of copper(n,ni) complexes with morpholinedithiocarbamato ligand Krishna Srivastava•, Ashish Kumar Srivastava, Dipiti Porwal and Jagdish Prasad Department of Chemistry, University of Allahabad, Allahabad-211 002, Uttar Pradesh, India E-mail : dr_krishna_s@yahoo.co.in Manuscript received 5 September 2007, accepted 7 September 2007 Abstract: The electrochemical behaviour of square planar [Cu 111 (rnorph-dtc) 2 ]CI0 4 (green), 1 and [Cu 11 (morph-dtc) 2 ] (brown), 2 (morph- dtc· = rnot·pholinedithiocarbamato anion) has been studied in dichloromethane (DCM), dimethylsulfoxide (DMSO), dimethylformamidc (DMF) and acetone containing 0.1 M TBAP as supporting electrolyte at a platinum disc working electrode using cyclic voltammetry. Two one-electron redox couples (Cul+ 12 +) and (Cu 2 + 1 +) corresponding to [Cu 111 (morph-dtc) 2 ]+ + r-+ [Cu 11 (morph-dtc) 2 ] in the positive potential region and [Cu 11 (morph-dtc) 2 ] + e--+ [Cu 1 (morph-dtc) 2 ]· in the negative potential region have been observed in DCM and DMSO media. In DMF and acetone, however, only a single quasircversible couple followed by an intense irreversible anodic peak, have been observed in the positive potential region. The present electrochemical studies reveal that the redox properties of complex 1 differ significantly in these solvents. It is observed that the case of reduction (Cul+ 12 +) of this complex decreases in the order : acetone (£'1 ' = 625 m V) -+ DCM (ElY= 605 mV)-+ DMSO (E'r = 500 mV)-+ DMF (E'r = 380 mV). Keywords : Electrochemistry, copper(n,m) complexes, dithiocarbamates, cyclic voltammetry. The coordination chemistry of high-oxidation state transition metal complexes is an area of considerable importance, because of their biological significance as models of redox enzymes and their potentially useful properties as catalytic oxidants 1 . One important feature of dithiocarbamate ligands is their ability to stabilize both high and low formal oxidation states (e.g. copper(m), nickel(Iv) and iron(Iv)) 2 • This is as a result of the delocalization that the ligand provides (Fig. I) and the consequential high electron density the sulfur donors present 3 • Dithiocarbamates, their metal complexes and their oxidation products, thiouramdisulfides have had numerous industrial uses; for example, they have acted as lubricants, antioxidants, fungkides and accelerators for rubber vulcanization and as drugs in medicine 4 • The dithiocarbamate (dtc) ligand has proved to be an extremely versatile and robust motif for metal-directed self- assembly. Its ease of formation and wide ranging coordination chemistry has led to the formation of an array of novel and complex supramolecular architectures. The use of the dithiocarbamate ligand has recently expanded to stabilizing gold nanoparticles and preparing multimetallic wires and arrays 5 . In our earlier paper we reported the cyclic voltammetric studies of some copper(n,m)-dithiocarbamates 6 . Here we report the electrochemical behaviour of copper(11) and copper(111) complexes with morpholinedithiocarbamate bidentate monoanionic ligand (morph-dtc-), viz. [Cu"'(morph-dtc) 2 ]Cl0 4 (green), 1 and [Cu 11 (morph-dtc) 2 ] (brown), 2. Both these complexes have square planar structures in which Cu 11 and Cull' are coordinated to four sulphur donor atoms 7 . Results and discussion The electrochemical studies of [Cu 111 (morph- dtc ) 2 ]Cl0 4 , 1 were carried out in dichloromethane (DCM), dimethylsulfoxide (DMSO), dimethylformamide (DMF) and acetone containing 0.1 M tetrabutyl ammonium perchlorate (TBAP) as a supporting electrolyte at a platinum disc working electrode using cyclic voltammetry (CV) technique. The CV experiments were also performed for [Cu(morph-dtc) 2 ], 2 in DCM/0.1 M TBAP medium for the sake of comparison. Typical cyclic voltammograms ofl in DCM, DMSO and DMF are shown in Figs. 2(a,b,c) at a scan rate 100 mY s- 1 and CV data are given in Tables 1 and 2. Fig. 1. Resonance structures of the morph-dtc· ligand. 1195