Syntheses and structures of nickel(II) and copper(II) complexes with biacetyl bis(benzoylhydrazone): one-dimensional self-assembly via π–π interaction and hydrogen bonding

Reactions of Ni(O2CCH3)2·4H2O and Cu(O2CCH3)2·H2O with biacetyl bis(benzoylhydrazone) (H2babh) in alcoholic media afford mononuclear nickel(II) and copper(II) complexes of general formula [M(babh)]. The complexes have been characterized by microanalysis (C, H, N), magnetic susceptibility, and various spectroscopic measurements. X-ray structures of both complexes have been determined. The metal centre in [Ni(babh)] is in square-planar N2O2 environment provided by the tetradentate babh2−. On the other hand, [Cu(babh)] crystallizes as distorted square-pyramidal [Cu(babh)(CH3OH)] from methanol. Here the tetradentate babh2− constitutes the N2O2 square-base and the O-coordinating methanol occupies the apical site. In the crystal lattice, the molecules of [Ni(babh)] form a one-dimensional π-stacked structure. The [Cu(babh)(CH3OH)] molecules also form a one-dimensional structure with alternating long and short Cu···Cu distances via intermolecular O–H···N hydrogen bonding and π–π interaction.