Nickel(II) complexes of biologically active glutathione: Spectroscopic, kinetics of thermal decomposition and XRPD studies

Nickel(II) complexes of reduced glutathione (GSH) of general composition Na[Ni(L)(X)]H2O, where H2L = GSH; X = NO3−, SCN−, CH3CO2−, Cl− have been synthesized and characterized by elemental analysis, infrared spectra, electronic spectra, magnetic susceptibility measurements, thermal and X-ray powder diffraction studies. Infrared spectra indicate deprotonation and coordination of cysteinyl sulphur and carboxylate oxygen of glycine residue with nickel ions. It indicates the presence of water molecule in all the complexes which has been supported by TG/DTA. The thermal behavior of complexes shows that water molecule is removed in first step-followed removal of anions and then decomposition of the ligand molecule in subsequent steps. General mechanisms describing the decomposition of the solid complexes are suggested. Kinetic and thermodynamic parameters were computed from the thermal decomposition data. The room temperature magnetic moment values for all the complexes lie in the range of 2.2-2.4 BM, indicating departure from spin only values due to second order Zeeman effect. The electronic spectra indicate planar coordination geometry for all the complexes. Crystal data for Na[Ni(L)(CH3CO2−)]H2O: tetragonal, space group P4/m, a = 8.2004 Å, b = 8.2004 Å, c = 16.0226 Å, V = 1077.47 Å3, Z = 2. Crystal data for Na[Ni(L)(Cl−)]H2O: cubic, space group Pm3, a = 16.1055 Å, b = 16.1055 Å, c = 16.1055 Å, V = 4178.38 Å3, Z = 6. Crystal data for Na[Ni(L)(NO3−)]H2O: tetragonal, space group P4/m, a = 7.2121 Å, b = 7.2121 Å, c = 12.0200 Å, V = 625.22 Å3, Z = 2.