Synthesis, spectral characterization and thermal aspects of coordination polymers of some transition metal ions with adipoyl bis(isonicotinoylhydrazone)

Abstract

A series of metal coordination polymers of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II), obtained by the reaction of metal acetate with newly synthesized adipoyl bis(isonicotinoylhydrazone) (ADBI) have been investigated. The ligand has been characterized by 1H NMR, 13C NMR, FTIR, and ESI mass spectra. Structural and spectroscopic characterization of the coordination polymers have been carried out using elemental analysis, XRD, SEM, infrared and diffused reflectance spectra, magnetic susceptibility measurements and thermogravimetric analytical techniques. Each metal ion is coordinated to the ligand through oxygen of carbonyl group and the nitrogen of azomethine group of ligand forming a stable 5-membered heterocyclic ring. The synthesized ligand coordinates in an octadentate manner. Magnetic and diffused reflectance spectral studies reveal octahedral geometry of Co(II), Cu(II), Fe(II) and Ni(II) coordination polymers and tetrahedral geometry of Mn(II) and Zn(II) coordination polymers. The thermal stability and decomposition steps of all coordination polymers have been studied using TG, DTG and DTA techniques. Moreover, the kinetic parameters such as activation energy (Ea*), order of reaction (n), Arrhenius factor (A), change in entropy (ΔS*), change in enthalpy (ΔH*) and free energy change (ΔG*) were evaluated at each stage of decomposition curve using Coats-Redfern method.