Abstract
4-Formylazohydrazoaniline antipyrine and its iron(III), cobalt(II), nickel(II) and copper(II) complexes have been synthesized and characterized by IR, electronic spectra, molar conductivities, magnetic susceptibilities and ESR. The ligand behaves as a neutral bidentate and tridentate ligand in the hydrate form or monobasic tridentate ligand in the enol-azo form. Coordination takes place via the carbonyl oxygen of the side chain, azomethine nitrogen atom for bidentate coordination. The carbonyl oxygen of the pyrazolone ring is added for tridentate coordination and enolic oxygen appears in monobasic tridentate coordination.