Electrochemical behaviour of polymeric complexes of monosubstituted squarate ligands. 1. Cyclic and square wave voltammetry of methylsquarate and diphenylaminosquarate complexes of cobalt and nickel

Cyclic voltammetric analysis of cobalt(II) methylsquarate in N,N-dimethylfo rmamide (DMF) and dimethylsulphoxide (DMSO) reveals the occurrence of simil ar redox processes in each solvent. In DMF, one cathodic and two anodic red ox processes, which are characteristic of the methylsquarate ligand, occur at - 1188, + 1094 and + 1398 mV, respectively. Co(I)/Co(II) and Co(II)/Co(I II) redox processes are also apparent. For cobalt(II) diphenylaminosquarate in DMF and DMSO, similar electrochemical processes occur but oxidation of Co(I) to Co(II) is more facile than for the methylsquarate complex in both solvents. Nickel(II) methylsquarate also shows ligand-based redox processes similar to the respective cobalt(II) complexes. Ni(I)/Ni(0) and Ni(II)/Ni( I) have been identified in the CV of this complex. In DMSO, there is eviden ce for partial dissociation of the nickel(II) methylsquarate complex. The r esults suggest that electron transfer occurs along the polymer chains in al l three complexes. (C) 2001 Elsevier Science Ltd. All rights reserved.