In this study, new 1:2 nickel complexes of 1-[o-, m-, p-(methyl, metoxyphenyl)]-3-(p-metoxyphenyl)-5-phenylformazans were synthesized. Their structures were elucidated and spectral behaviors were investigated with the use of elemental analysis, GC-mass, H-1 NMR, C-13 NMR, IR, and UV-vis spectra. The redox characteristics of these compounds have been investigated in nonaqueous dimethylsulfoxide at platinum and ultramicro platinum (10 mu m) electrodes. Through controlled potential electrolysis, the oxidation products of each class of compounds can be separated and identified. The oxidation mechanism is suggested and it is proved. It was observed the oxidation mechanism take place in a single step two-electron or one-electron transfer to a disproportionation or dimerization reactions following the radical formation step. Eventually the relation between their absorption properties and electrochemical properties was examined. (C) 2008 Elsevier Ltd. All rights reserved.