Experimental and theoretical structural determination, spectroscopy and electrochemistry of cobalt (III) Schiff base complexes: immobilization of complexes onto Montmorillonite-K10 nanoclay

Abstract

The [Co(5-XSalen)(PEt3)(H2O)]ClO4 (where Salen = bis(salicylaldehyde)1,2-ethylenediamine and X = H, MeO, NO2, Br) complexes were successfully synthesized and characterized by different techniques such as FT-IR, UV–Vis, 1HNMR, 13CNMR and 31PNMR. The coordination geometry of the [Co(5-BrSalen)(PEt3)(H2O)]ClO4 complex was determined by X-ray crystallography. The complex has six-coordinated pseudo-octahedral geometry in which the O(1), O(2), N(1) and N(2) atoms of the Schiff base form the equatorial plane. The cyclovoltammetry was used to study the electrochemical properties of cobalt complexes, and the results reveal the anodic peak potential becomes more positive in order to MeO < H < Br < NO2. DFT calculations were also done to investigate structures, electronic spectra and infrared spectra of the complexes. The synthesized complexes [Co(Salen)(PEt3)(H2O)]ClO4, [Co(Salen)(PBu3)(H2O)]ClO4 and [Co(5-NO2Salen)(PEt3)(H2O)]ClO4 were incorporated within Montmorillonite-K10 (MMT) nanoclay. Furthermore, structural, thermal and morphological properties of the prepared nanohybrids were verified by FT-IR, XRD, TGA-DTG, EDX, SEM and TEM techniques. XRD results of the new nanohybrid materials elucidate that the Schiff base complexes were placed at the most outerlayer spaces of MMT clay.