X-ray crystallography, electrochemistry, spectral and thermal analysis of some tetradentate schiff base complexes and formation constant measurements

ABSTRACT

A series of new transition metal Schiff base complexes was synthesized via the reaction of H₂L (N,N′-bis(naphthylidene)-2-aminobenzylamine) with the transition metals (Cu²⁺, Co²⁺, Ni²⁺, Zn²⁺ and Mn²⁺) and characterized by elemental analysis, ¹HNMR, FT-IR, UV-Vis spectroscopy, thermogravimetric analysis(TG) and in selected cases by X-ray crystallography. Thermodynamics of complex formation, electrochemistry of the metal Schiff base complexes and kinetic aspects of thermal decomposition of the complexes were also studied. The obtained formation constants change according to the following trend due to the electronegativity and Jahn-Teller effects of the central transition metals: Cu > Co > Ni > Zn >Mn. Cyclic voltammogram of the complexes in acetonitrile was done to evaluate the redox behavior of the complexes. Electrochemistry of these complexes showed a redox reaction without any successive reactions. Furthermore, kinetic parameters which calculated by Coats–Redfern equation revealed a first-order kinetics of thermal decomposition in all stages.

KEYWORDS:

• X-ray crystallography
• transition metal Schiff base complexes
• thermogravimetry
• electrochemistry
• formation constant measurements

Acknowledgments

Financial support by the Shiraz University is gratefully acknowledged. The project 15-12653S of the Czech Science Foundation supported the crystallographic part of the work.