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

Copper(II) complexes of 2-di1H-2-imidazolylmethylmalonate (DIMMAL) have been studied by potentiometric methods. The data revealed that the CuHL2- and CuL22- 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)] center dot 4H(2)O (1) and [Cu(DIMMAL)(en)(H2O)] center dot 5H(2)O (2). The structure of compound 1 consists of centrosymmetric mononuclear anionic [Cu(DIMMAL)(2)](2-) units, NH4+ cations and lattice water molecules, in which DIMMAL 2- 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 d(x2-y2) ground state for the copper(II) ions in both compounds (CuN4O2 chromophores). (c) 2007 Elsevier Ltd. All rights reserved.