Extended structures of copper(II) complexes with 2-di1H-2-imidazolylmethylmalonate (DIMMAL), a versatile bis(imidazole)–bis(carboxylate) ligand: Solution studies, crystal structures and spectroscopic characterization

Abstract: Copper(II) complexes of 2-di1H-2-imidazolylmethylmalonate (DIMMAL) have been studied by potentiometric methods. The data revealed that the and species are prevalent in the studied pH range. Moreover, this paper reports the synthesis, structure solution and spectroscopic characterization of two new DIMMAL containing complexes, (NH4)2[Cu(DIMMAL)2]·4H2O (1) and [Cu(DIMMAL)(en)(H2O)]·5H2O (2). The structure of compound 1 consists of centrosymmetric mononuclear anionic [Cu(DIMMAL)2]2− units, cations and lattice water molecules, in which DIMMAL2− acts as a tridentate ligand through two imidazole nitrogen atoms and one oxygen atom from a carboxylate group. The crystal structure of compound 2 is built up from mononuclear neutral [Cu(DIMMAL)(en)(H2O)] and water molecules of crystallization. In both cases the MBBs are interconnected into 3D networks by multiple H-bonding paths and aromatic–aromatic interactions, which play a determinant role in the modulation of the crystal packing. EPR spectra are indicative of an essentially ground state for the copper(II) ions in both compounds (CuN4O2 chromophores). [Copyright &y& Elsevier]