A molecular butterfly: Self-assembly of an imidazolate bridged tetranuclear nickel(II) compound from Ni(II) and 3-(4-methylimidazol-5-yl)methylene-hydrazonobutan-2-one oxime

Reaction of the Schiff-base ligand, 3-(4-methylimidazol-5-yl)methylenehydrazonobutan-2-one oxime (H2L) with nickel(II) perchlorate hexahydrate in 1:1 molar proportion in methanol gives rise to a tetranuclear nickel(II) compound, Ni4L4 (1) in moderate yield. The compound has been characterized by C, H, N microanalyses, FT-IR, UV–Vis spectra and room temperature magnetic susceptibility measurements. The X-ray crystal structure of the title compound has been determined. The structure reveals that it is an imidazolate bridged neutral tetranuclear nickel(II) compound. The nickel(II) centers in 1 adopt a rare ‘butterfly-like’ topology. The compound crystallizes in the monoclinic space group P21/c with a = 17.648 (4), b = 23.209 (5), c = 14.418 (3) Å, β = 108.708 (2)°, V = 5593 (2) Å3 and Z = 4. Individual nickel(II) center is in square-planar ‘N4’ coordination chromophore. Electrochemical studies show Ni(II) to Ni(III) oxidation along with Ni(II) to Ni(I) reduction in dichloromethane solution. Bond-Valence Sum (BVS) model calculation was performed to assign the oxidation state of each nickel center in 1.

A tetranuclear nickel(II) compound Ni4L4 (1) with 3-(4-methylimidazol-5-yl)methylenehydrazonobutan-2-one oxime (H2L) have been synthesized and characterized. The X-ray crystal structure of 1 reveals that it is an imidazolate bridged neutral tetranuclear Ni(II) compound. Each nickel center in 1 is in square-planar ‘N4’ coordination environment. The compound is essentially diamagnetic. The nickel(II) centers in 1 adopt a rare ‘butterfly-like’ topology. Electrochemical studies show Ni(II) to Ni(III) oxidation along with Ni(II) to Ni(I) reduction in dichloromethane solution. Semi-empirical Bond-Valence Sum (BVS) method of analyses were also undertaken to assign the oxidation state of each nickel center in 1.Figure optionsDownload as PowerPoint slideHighlights
► Schiff-base ligand.
► Synthesis of tetranuclear nickel(II) complex.
► X-ray crystallography.
► Electrochemical studies.
► BVS calculation.