In this study, 1-[o-, m-, p-(chloro, bromo)]-3-(m-nitrophenyl)-5-pheny[formazans were synthesized. Their structures were elucidated and spectral behaviors were investigated using elemental analysis, GC-mass, H-1 NMR, C-13 NMR, FTIR and UV-vis spectra. Electrochemical properties of formazans such as number of electrons transferred (n), diffusion coefficient (D) and heterogeneous rate constant (k(s)) of the compounds were determined and possible mechanisms were proposed with the use cyclic voltammetry, ultramicrodisc electrode and chronoamperometry. The relation between their absorption properties and electrochemical properties was sought. 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. A correlation was obtained between lambda(max) with Hammett substituent coefficient, E-ox1 and E-red1. (C) 2008 Elsevier B.V. All rights reserved.