Synthesis and spectroscopic properties of 3-hydroxy-3-phenyl-1-o-carboxyphenyltriazene and its copper(II), nickel(II) and zinc(II) complexes

3-Hydroxy-3-phenyl-1-o-carboxyphenyltriazene (HT) is synthesized by coupling diazonium salt of 2-aminobenzoic acid with phenylhydroxylamine in 1:1 molar proportion at 0-5°C. The reagent forms 1:2 metal complexes with Cu(II), Ni(II) and Zn(II) ions in sodium acetate buffer (∼pH 5). All these complexes are quite stable in solutions. The reagent and the complexes are characterized by spectral methods viz., UV-vis, FTIR, 1 HNMR, 1 3 CNMR and luminescence spectra. The cis- and trans-[Ni(HT) 2 ] 0 complexes have been separated and determined by 1 HNMR technique. The L→M and M→L charge transfer character of the complexes is also studied by 1 HNMR technique. The mechanism of excited state electron transfer and energy transfer of the ligand has been investigated to explain the formation of tautomeric isomers of HT which led to the application of these donor-acceptor systems in molecular electronics.