Cadmium(II) complexes containing N,N´-dimethylvioluric acid as ligand or counteranion: Synthesis, characterization, crystal structures and DFT study

Abstract

[eng] N,N0-dimethylvioluric acid mono hydrate (HDMV) (1$H2O) and two cadmium(II) complexes with N-donor ligands of formula [Cd(DMV)2(benzim)2]$2H2O (2) (benzim ¼ benzimidazole) and [Cd(H2O)4(py)2](DMV)2 (3) (py ¼ pyridine) have been synthesized. Free N,N0-dimethyl violuric acid mono hydrate (HDMV) and the complexes have been fully characterized by elemental analysis, IR, 1H and 13C NMR spectral methods, fluorescence spectroscopy, TGA and structural X-ray crystallography. HDMV (1$H2O) which remains in keto-oxime form in the solid state transforms to the nitroso-enolato form in the complexes [(2) and (3)]. A typical R1 2(6) motif with a bifurcating hydrogen bond is observed in all three structures. Dimethylviolurate anion acts as a bidentate ligand in (2), whereas in (3) it is present as a counter-ion, outside the coordination sphere. In addition, DFT-D3 calculations have been performed to study interesting noncovalent interactions observed in the solid states of (1) and (2) with special interest in the lone pair (lp)-p interactions and their interplay with p-p interactions.