Supramolecular interactions through lone pair(lp)–π and hydrogen bonding in cobalt(III) and manganese(II) derivatives of N,N′-dimethylvioluric acid: A combined experimental and theoretical study

Abstract

The reactivities of cobalt(II) and manganese(II) salts toward HDMV (N,N′-dimethylvioluric acid monohydrate) were studied. Reaction of cobalt(II) chloride hexahydrate with HDMV in water–methanol medium at pH=8.0 led to the formation of a cobalt(III) complex [CoIII(DMV)3]·0.5H2O (1), whereas the interaction of manganese(II) chloride tetrahydrate with HDMV under similar reaction conditions afforded [MnII(H2O)6](DMV)2 (2). Dimethylviolurate anion behaves as a bidentate ligand in 1 and counteranion in 2. Both compounds were characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, cyclic voltammetry and thermogravimetric analysis. Presence of Co(III) in 1 indicates the aerial oxidation of the cobalt(II) precursor. In 1, Co(III) adopts a distorted octahedral [CoN3O3] coordination environment through bonding to the three dimethylviolurato anions. In 2, the [Mn(H2O)6]2+ cations and (DMV)− anions are assembled by multiple hydrogen bonds into a complex 3D H-bonded network. It was analyzed from the topological viewpoint, disclosing a binodal 4,8-connected underlying net with the flu (fluorite) topology. Electrochemical studies reveal that the compounds undergo a quasi-reversible one electron metal centered redox process. DFT studies were carried out to analyze the supramolecular assemblies in the solid state structures, especially lone pair(lp)–π interactions in 1 and H-bonding network in 2.