Synthesis and thermal studies of mixed ligand complexes of Cu(II), Co(II), Ni(II) and Cd(II) with mercaptotriazoles and dehydroacetic acid

A series of new mixed ligand complexes of cobalt(II), nickel(II), copper(II) and cadmium(II) have been synthesized with 3-benzyl-1H-4-[(2methoxybenzylidine) amino]-1, 2, 4-triazole-5thione (MBT), 3-bezyl-1H-4-[(4-chlorobenzylidine) amino]-1, 2, 4-triazole-5-thione (CBT), 3-benzyl1H-4-[(4-nitrobenzylidine)amino]-1, 2, 4-triazole5-thione (NBT) and dehydroacetic acid sodium salt (Nadha). The mixed ligand complexes have been characterized by elemental analysis, spectroscopic spectral measurements (IR, UV-Vis.), molar conductance, magnetic measurements and thermal studies. The stoichiometry of these complexes is M:L1:L2 = 1:1:1, 1:2:1 or 1:1:2 where L1 = NBT, CBT and MBT and L2 = Nadha. Tetrahedral structure was proposed for all Cd(II) mixed ligand complexes while the square planar geometry was proposed for Cu(II) mixed ligand complex with NBT. Octahedral structure was proposed for Ni(II), Co(II) mixed ligand complexes and Cu(II) mixed ligand complexes with CBT and MBT ligands. The thermal decomposition study of the prepared complexes was monitored by TG, DTG and DTA analysis in dynamic nitrogen atmosphere. TG, DTG and DTA studies confirmed the chemical formulations of theses complexes. The kinetic parameters were determined from the the thermal decomposition data using the graphical methods of Coats-Redfern and Horwitz-Metzger. Thermodynamic parameters were calculated using standard relations.