Structural characterization and magnetic properties of hexakis(imidazole)nickel(II) bis(formate), bis(chloroacetate), bis(2-chloropropionate) and hexakis(1-methyl-imidazole)nickel(II) chloride dihydrate

The nickel(II) complexes of formula [Ni(iz)6]X2, (where iz = imidazole, and X = formate, chloroacetate and 2-chloropropionate anions) have been prepared and characterized by spectroscopic methods and magnetic measurements. The crystal and molecular structure of [Ni(iz)6](HCOO)2, 1, [Ni(iz)6](ClCH2COO)2, 2 and [Ni(iz)6](CH3ClCHCOO)2, 3 have been determined by X-ray diffractions methods. The structure of the all complexes is formed by a three-dimensional network consisting of [Ni(iz)6]2+ cations interlinked by formate, chloroacetate and 2-chloropropionate anions through three different N–H⋯O bonds, in which all the N–H imidazole units, as well as all the carboxylate O atoms, take part. The Ni atom is in a nearly octahedral environment formed by the tertiary nitrogen atom of the imidazole moieties. An analogous complex [Ni(Meiz)6]Cl2 · 2H2O (4) shows a two-dimensional hydrogen-bond network in which only four ligands take part along with Cl− and H2O units. The distortion of Ni2+ coordination polyhedron rises in the order of 1(negative) < 2 < 3(positive) < 4. The magnetism of complexes exhibits a zero-field splitting D, the magnitude of which correlates with the distortion degree of the coordination polyhedra.

The crystal and molecular structure of [Ni(iz)6](HCOO)2, [Ni(iz)6](ClCH2COO)2, [Ni(iz)6](CH3ClCHCOO)2, and [Ni(Meiz)6]Cl2 · 2H2O has been determined by single crystal X-ray analysis along with the spectral characteristics and magnetic measurements down to 2 K. The tetragonality in these complexes is generally small, Dstr between −5.2 to +3.5 pm and the magnetic anisotropy Dmag is between −3.4 to +2.0 cm−1. A straight-line type of the correlation has been found: the greater the tetragonality Dstr, the greater the axial zero-field splitting parameter Dmag.Figure optionsDownload as PowerPoint slide