Spectroscopic, Cyclic Voltammetry, Thermal and Biological Activity Studies of Co(II), Ni(II) and Cu(II) Complexes of Novel Azo Dyes Derived from Thiadiazole Compounds

Novel complexes obtained by reaction of [5-phenyl[1,3,4]thiadiazol-2-yl]azo-4- resorcinol (L1) and [5-phenyl[1,3,4]thiadiazol-2-yl]azo- -naphthol (L2) with Co(II), Ni(II) and Cu(II) have been synthesized and characterized by elemental analysis, molar conductance, electronic, IR and TGA studies as well as cyclic voltammetry. These complexes have the general formula [M(L)Cl22H2O]nH2O and [M(L)2Cl2]nH2O whereM= Cu(II), Ni(II), or Co(II) and L = L1 or L2. It was found that the free ligands are neutral bidentate ON donors of carbonyl and azo groups. The stoichiometry of these complexes is M:L= 1:1 and 1:2. TG studies of these complexes showed that thermal degradation proceeds in two steps. Octahedral geometry is proposed for the divalent metal complexes, cyclic voltammetry reveals a reversibility of the CuII/CuI couple, while for the CoII and NiII complexes there was no reaction. It is observed that the chelates formed are more potent as antimicrobial agents than the free ligands. The stability constants of these complexes determined by spectroscopy methods change in the following sequence: Co(II) < Ni(II) < Cu(II).