Thermal stability, synthesis of new formazan complexes derived from thiophene-2-carboxaldehyde

A novel formazan ligand was prepared from the condensation of p-phenylenediamine and thiophene-2-carboxaldehyde with diazonium salt of 4-chloro aniline, and its metal transition complexes of Co (II), Cu (II) and Ni (II) were synthesized from the reaction of the metal chlorides with the formazan ligand in the molar ratio of 1:1 (M: L). The formazan ligand and its metal complexes were identified by different spectroscopic and analytical techniques. The results of this study suggested that the metal complexes had a tetrahedral geometry. Thermogravimetric analysis was used to study the thermal decomposition of the complexes. The results showed that all the steps were non-spontaneous, as evidenced by the positive ΔG values; the decomposition process was endothermic, as evidenced by the positive ΔH values; and the complexes were more ordered than the reactants, as evidenced by the negative ΔS values. The thermodynamic data (ΔH, ΔS, ΔG) were calculated by using the Coats-Redfern equation.