Synthesis and structure of mononuclear Cu(II) complexes containing bis(1-methylimidazol-2-yl)ketone ligands

Two mononuclear copper(II) compounds containing bis(1-methylimidazol-2-yl)ketone (BIK) were synthesized, structurally characterized by X-ray structure analysis and investigated by UV–Vis and IR spectroscopy, electrochemistry and thermogravimetry analysis (TGA). One complex [Cu(BIK)(ac)2] (1) results from a copper(II) acetate to BIK stoichiometric ratio of 1:1, whereas a 1:2 ratio leads to complex (Cu(BIK)2(ac))+ (2). Complex 1 containing one BIK ligand shows a Jahn–Teller distorted [4+2] geometry of the Cu(II) atom being coordinated by the two nitrogen atoms from the BIK ligand (1.981 Å) and by two oxygen atoms from two acetate units in a distance of 1.966 Å and two other oxygen atoms from the same group in a longer distance of 2.550 Å. Compound 2 crystallizes in the triclinic system P 1 ¯ , with two independent molecular units. Both copper atoms are distorted [4+1+1] coordinated by four N atoms from the two molecules of the bidentate BIK ligand and two O atoms from the coordinated acetate group in average distances of 1.97 and 2.85 Å, respectively. In complex 2 a hydrogen bonding network is formed by H2O molecules and acetate groups. From TGA it was found that dehydration occurs in two steps at 39 °C and at 115 °C.