Synthesis and characterization of mononuclear copper(II) aspirinate adducts with imidazole and its methyl derivatives

Abstract

A synthetic investigation of copper(II) aspirinate addition compounds with imidazoles has led to the isolation of monomers of the form [Cu(asp)2 · Ln], where asp is the aspirinate anion and n = 4 when L is imidazole or N-methylimidazole and n = 2 when L is 1,2-dimethylimidazole. These compounds have been characterized by means of elemental analysis, magnetic moments, electronic, IR and ESR spectroscopic properties. The tetrakis-adducts of imidazole and N-methylimidazole showed physical properties which indicated a tetragonal six-coordinated configuration containing the (CuN4+O2) chromophore. For the bis-adduct of 1,2-dimethylimidazole, the proposed geometry is a tetragonal distorted octahedron, having essentially the CuN2O2 chromophore in a trans distorted square-planar environment. The adoption of monomeric rather than the more common dimeric structure is discussed in terms of the electronic and steric effects of these imidazole ligands