Structural, vibrational, thermal and magnetic investigation of novel Co(II), Cu(II), Zn(II) and Hg(II) crystalline metal complexes with 2-amino-5-benzylmercapto-1,3,4-thiadiazole: a low weight model of protonated copolymer resin

The 2-amino-5-benzylmercapto-1,3,4-thiadiazole (C9H9N3S2) is a low weight model of a protonated copolymer resin used as a metal uptake agent. New monomeric crystalline metal complexes of C9H9N3S2 with Co(II), Cu(II), Zn(II) and Hg(II) were synthesized and investigated in order to facilitate the interpretation of the metal/resin binding mode. These materials have been studied by single crystal X-ray Diffraction and FTIR Spectroscopy at room temperature. Crystal data for these triclinic phases are reported. All frameworks consist of discrete monomeric units that provide crystalline stability through a network of hydrogen bond interactions. The Co(II), Zn(II) and Hg(II) ions are surrounded by a tetrahedral arrangement of two thioether monodentate ligands (each one coordinating by a N(1)thiadiazole atom) and two chlorine atoms. The Cu(II) ion is coordinated by four thioether monodentate ligands (each one coordinating by a N(1)thiadiazole atom) and one chlorine atom as nearest neighbor in a distorted square pyramidal polyhedron. The spectroscopic data are consistent with the structural model. FTIR spectra evidence changes in the H-bonds in the crystal packing when coordination with these divalent ions is present. Magnetic susceptibility at room temperature for Cu(II) and Co(II) complexes, EPR spectrum at room temperature for Cu(II) complex and thermal properties for all complexes were measured. These results could be useful for the interpretation of the binding mode of M(II)/1,3,4-thiadiazole-2-amino-5-thiol in protonated copolymer resin which are used as uptake agents of toxic metallic ions.