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] · 4H2O (1) and [Cu(DIMMAL)(en)(H2O)] · 5H2O (2). The structure of compound 1 consists of centrosymmetric mononuclear anionic [Cu(DIMMAL)2]2− units, NH4+ 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 dx2−y2dx2−y2 ground state for the copper(II) ions in both compounds (CuN4O2 chromophores).

Graphical abstractCopper(II) complexes of 2-di1H-2-imidazolylmethylmalonate (DIMMAL) have been studied by potentiometric methods. Beside this, the synthesis, characterization and structure solution of two new complexes based on this novel bis(imidazole)–bis(carboxylate) ligand are reported. Non-covalent interactions (H-bonds and π–π) drive the build-up of infinite three-dimensional arrays in both compounds.Figure optionsDownload full-size imageDownload as PowerPoint slide