Iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) complexes of 4-formylantipyrine thiosemicarbazone

Complexes of iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) with 4-formylantipyrine thiosemicarbazone (HFoAtsc) have been prepared and spectrally and physically characterized. IR, electronic, and ESR spectra of the complexes, as well as IR, electronic and ¹H and ¹³C NMR spectra of HFoAtsc, have been obtained. The spectral studies show that HFoAtsc behaves as neutral or monobasic bidentate ligand in all complexes except [Fe(FoAtsc)₂]ClO₄ and [Co(HFoAtsc)₂](BF₄)₂, where the thiosemicarbazone bonds in a monobasic tridentate fashion in the former and a neutral tridentate manner in the latter. Coordination takes place via the azomethine nitrogen and the thione or thiolato sulfur for bidentate coordination and the carbonyl oxygen of the pyrazolone ring is added for tridentate coordination.