In this study, 3-substitutedphenyl-1,5-diphenylformazans were synthesized with -NO2 and -COOH groups in the o-, m- and p- positions of the 3-phenyl ring. Their structures were elucidated from elemental analysis , H-1 NMR, C-13 NMR and IR spectra. The dependence lambda(max) upon the type of the substituents and their positions on the phenyl ring was investigated using UV-vis spectra. If was observed that there was a shift of lambda(max) towards the blue region with the electron withdrawing -NO2 and -COOH groups. The size of this' chemical shift (Deltalambda(max)) was dependent upon the type and position of the substituent on the 3-phenyl ring. A linear relation was obtained between the substituent effect and the Hammett substituent coefficients. (C) 2002 Elsevier Science Ltd. All rights reserved.