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 04 atoms is observed. These complexes present the form (MCl2L)-Cl-II 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(MLM)(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. (C) 2003 Elsevier Science B.V. All rights reserved.