Synthesis, characterisation and crystal structures of a few coordination complexes of nickel(II), cobalt(III) and zinc(II) with N′-[(2-pyridyl)methylene]salicyloylhydrazone Schiff base

Four new coordination complexes, NiII(L)2 (1), [CoIII(L)2]ClO4 (2), [Zn(HL)(L)]ClO4 · H2O (3) and [Zn(L)2][Zn(L)(HL)]ClO4 · 7H2O (4) (where L is a monoanion of a Schiff base ligand, N′-[(2-pyridyl)methylene]salicyloylhydrazone (HL) with NNO tridentate donor set), have been synthesised and systematically characterised by elemental analysis, spectroscopic studies and room temperature magnetic susceptibility measurements. Single crystal X-ray diffraction analysis reveals that 1 is a neutral complex, while 2–4 are cationic complexes. Among them, 4 is a rare type of cationic complex with two molecules in the asymmetric unit. The ligand chelates the metal centre with two nitrogen atoms from the pyridine and imino moieties and one oxygen atom coming from its enolic counterpart. All the reported complexes show distorted octahedral geometry around the metal centres, with the two metal–N (imino) bonds being significantly shorter than the two metal–N (Py) bonds.

Graphical abstractA few neutral and cationic Ni(II), Co(III) and Zn(II) complexes have been synthesised with N′-[(2-pyridyl)methylene]salicyloylhydrazone Schiff base. They have been systematically characterised and structures have been confirmed from single crystal X-ray diffraction study. In the complexes, ligand behaves as neutral, anionic or both in their chelation modes tautomerising between ketonic and enolic forms. One of the Zn(II) complexes is a novel one where two dissymmetrical units are hydrogen bonded through the intercalated water molecules.Figure optionsDownload full-size imageDownload as PowerPoint slide