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-di1 H -2-imidazolylmethylmalonate (DIMMAL) have been studied by potentiometric methods. The data revealed that the CuHL 2 - and CuL 2 2 - 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, (NH 4 ) 2 [Cu(DIMMAL) 2 ] · 4H 2 O ( 1 ) and [Cu(DIMMAL)(en)(H 2 O)] · 5H 2 O ( 2 ). The structure of compound 1 consists of centrosymmetric mononuclear anionic [Cu(DIMMAL) 2 ] 2− units, NH 4 + 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)(H 2 O)] 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 x 2 −y 2 d x 2 − y 2 ground state for the copper(II) ions in both compounds (CuN 4 O 2 chromophores).