Synthesis and characterization of several lumazine derivative complexes of Co(II), Ni(II), Cu(II), Cd(II), Pd(II) and Pt(II). X-ray structures of a mononuclear copper complex and a dinuclear cadmium complex

The synthesis of the new Co(II), Ni(II), Cu(II), Cd(II), Pd(II) and Pt(II) complexes with 1-methyllumazine (1-methylpteridine-2,4(1H,3H)-dione, MLM) and 1,6,7-trymethyllumazine (1,6,7-trimethylpteridine-2,4(1H,3H)-dione, MLMD) is described. The coordination chemistry of these ligands have been investigated and an usual bidentate bonding mode through the N5 and O4 atoms is observed. These complexes present the form MIICl2L and were characterized by elemental analyses, TG and DSC, as well as by IR, UV–Vis, EPR spectroscopy and magnetic measurements. The crystal structures of [CuCl2(MLMD)(H2O)] and [CdCl2(MLM)(H2O)]2 have been determined by X-ray diffraction methods. The copper(II) compound exists in the monomeric form with an environment around the metal ion as a distorted square-based pyramidal geometry whereas the cadmium complex was observed as dimers with an edge-sharing distorted octahedral coordination sphere around each cadmium center.