Square-planar nickel(II) complexes with a tridentate Schiff base and monodentate heterocycles: self-assembly to dimeric and one-dimensional array via hydrogen bonding

Two nickel(II) complexes having the general formula [Ni(bhac)L] with tridentate ONO-donor acetylacetone benzoylhydrazone (H2bhac) and monodentate N-donor heterocycles (L=3,5-dimethylpyrazole (Hdmpz) and imidazole (Himdz)) are reported. The complexes were synthesized in ethanol media by reacting Ni(O2CCH3)2·4H2O, H2bhac and L in 1:1:1 mole ratio and characterized by analytical, magnetic and spectroscopic methods. X-ray crystal structures of both complexes have been determined. In each complex, the metal ion is in square-planar N2O2 coordination geometry. In the solid state, a one-dimensional assembly of the [Ni(bhac)(Himdz)] molecules is formed via intermolecular hydrogen bonds between the imidazole N–H groups and the uncoordinated N-atoms of the deprotonated amide functionalities. On the other hand, two [Ni(bhac)(Hdmpz)] molecules are involved in a pair of complementary hydrogen bonds between the pyrazole N–H groups and the coordinated O-atoms of the deprotonated amide functionalities forming a dinuclear species.