Divalent cobalt, copper and zinc complexes of (2Z,2′Z)-2,2′-(oxalylbis (hydrazin-2-yl-1-ylidene))dipropionic acid (H4OPA): Synthesis, characterization, computational, conductometric titration and biological potency

A new series of Co(II), Cu(II) and Zn(II) complexes have been synthesized with (2Z,2 ' Z)-2,2 '-(oxalylbis(hydrazin2-yl-1-ylidene))dipropionic acid (H4OPA). Specific spectroscopic methods used for the investigation of the prepared solid compounds' structure. The results of analytical and spectroscopic investigation revealed that ligand behaves as neutral tetradentate, binegative hexadentate and tetra-negative hexadentate with Cu(II), Co(II) and Zn(II) metal ions, respectively. The 1:1 binding manner between ligand, H4OPA and Cu2+ ions was evaluated by Job-plot technique. By applying the DFT theory, the optimized structures of the complexes were verified. In order to determine the kinetic and thermodynamic parameters by Horowitz-Metzger and Coats-Redfern approaches, thermal degradation curves for Co(II) complex was discussed. Furthermore, the association and formation constants as well as their Delta G values energies of Co(II) and Cu(II) complexes have been evaluated at 298.15 K in a 5% mixture of DMSO and ethanol. The conductometric results showed that the formation of Co(II) metal ion was (1:2) (L/M) but, the metal ion Cu(II) exhibits (1:3) (L/M) formation ratio. Moreover, all isolated compounds have been tested for biological potency shows that Zn(II) complex had the highest biological activity.

Automated summary

A new series of Co(II), Cu(II) and Zn(II) complexes were synthesized with specific spectroscopic methods used to investigate the structure. Different coordination modes of the ligand in different metal ions, thermal degradation curves and biological activities of the complexes were studied, revealing unique properties of the synthesized compounds.