Synthesis, characterization and magnetochemical studies of some imidazole and imidazolate copper(II) complexes derived from N-salicylideneacetylhydrazine: X-ray crystal and molecular structures of [imidazole-(N-salicylidenatoacetylhydrazinato)-ONO′ (-2)]copper(II) and potassium [mono(μ-imidazolate) bis(N-salicylidenatoacetylhydrazinato)] dicopper(II)

Abstract

Three new copper(II) complexes, [Cu(Sah)HIm], [Cu(HSah)Cl·HIm] and K[{Cu(Sah)}2Im], have been prepared and characterized by elemental analyses, infrared and ultraviolet–visible spectroscopy (HSah and Sah refer to mono- and dinegative N-salicylideneacetylhydrazine anions, respectively, while HIm and Im refer to neutral imidazole and mononegative imidazolate anion). The X-ray crystal and molecular structures of [Cu(Sah)HIm] and K[{Cu(Sah)}2Im] have been determined. In [Cu(Sah)HIm], the copper(II) atom is in a distorted square-planar environment and coordinated to the hydrazone ligand via phenoxy oxygen, imine nitrogen and deprotonated enolimine oxygen. The fourth coordination site is occupied by the imidazole nitrogen. The imidazole N–H is involved in an intermolecular hydrogen bond with the hydrazide nitrogen forming a 1-D supramolecular structure. In the (μ-imidazolate) dicopper(II) complex K[{Cu(Sah)}2Im], each copper(II) atom is in a distorted square-planar environment where the hydrazone ligand acts as an ONO tridentate dianion. The imidazolate anion acts as a bridged coligand connecting the two tricoordinated copper(II) units. The K+ is six coordinate, coordinated to four (μ-imidazolate) dicopper(II) units giving rise to a supramolecular network. Both [Cu(Sah)HIm] and [Cu(HSah)Cl·HIm] show normal magnetic moments of 1.82 and 1.85 µβ respectively. The dicopper complex K[{Cu(sah)}2Im] shows antiferromagnetic spin–spin coupling mediated via the μ-imidazolate with −J = 17.0 cm−1.