Synthesis, characterization, electrical and catalytic studies of some coordination compounds derived from unsymmetrical Schiff base ligand

G B Pethe,A R Yaul,A S Aswar

doi:10.4314/bcse.v29i3.6

Abstract

New unsymmetrical tetradentate Schiff base ligand derived from 5-chloro-2-hydroxyacetophenone, 2-hydroxy-5-methyl-3-nitro acetophenone and carbohydrazide and its complexes with VO(IV), Cr(III), Mn(III), Fe(III), MoO2(VI), WO2(VI), Zr(IV) and UO2(VI) have been prepared. They were characterized by elemental analysis, IR and electronic spectra, magnetic susceptibility measurements and thermal analyses. The Schiff base ligand has also been characterised by 1H-NMR spectroscopy. The thermal behaviour of metal complexes shows that the hydrated complexes lose water molecules of hydration in the first and then is immediately followed by decomposition of ligand molecule in the subsequent steps. The IR spectra suggest that ligand acts as dibasic tetradentate nature and coordination takes place through azomethine nitrogen and phenolate oxygen. The crystalline nature of the VO(IV) complex was conformed through the powder XRD analysis. The catalytic activity of the VO(IV) and Mn(III) complexes have been tested in the epoxidation reaction of styrene and conversion of styrene were 11.14-24.35% and 9.64-23.42%, respectively. The solid state electrical conductivity of ligand and its complexes were measured, which could obeyed the relation s = s0 exp (Ea/KT) over the temperature range 313-413 K. KEY WORDS: Schiff base, Metal complexes, TGA, Electrical conductivity, XRD, Oxidation of styrene Bull. Chem. Soc. Ethiop. 2015, 29(3), 387-397. DOI: http://dx.doi.org/10.4314/bcse.v29i3.6

Highlights

The Schiff base ligands are an important class of organic ligands in coordination chemistry, which increase the chemical and biological aspects of the compounds because they act as antibacterial, antiviral, antifungal agents, as homogeneous or hetrogeneous catalysts and display magnetic properties [1,2,3,4]
Considerable attention has been paid to the chemistry of the metal complexes of with symmetrical Schiff base ligands containing N and other donors atoms
Very little information is available for metal complexes of unsymmetrical Schiff base ligands [6,7,8,9]

Summary

Introduction

The Schiff base ligands are an important class of organic ligands in coordination chemistry, which increase the chemical and biological aspects of the compounds because they act as antibacterial, antiviral, antifungal agents, as homogeneous or hetrogeneous catalysts and display magnetic properties [1,2,3,4]. The FT-IR spectrum of the free ligand shows characteristic band at 2998 cm-1, assignable to (OH) intramolecular hydrogen bonding between phenolic hydrogen and azomethine nitrogen atoms, which disappears in the spectra of metal complexes, indicating deprotonation of the OH group upon binding with metal ions.

Results

Conclusion