Schiff Base Modified Chitosan Iron(III) Complex as new Heterogeneous Oxidative Catalyst

Abstract

A readily available biopolymeric chitosan has been shown to be a very promising supportive bioligand for the immobilization of catalytic metals. In this study, 3,6-diacetylnaphtalene-2,7-diol cross linked chitosan was used to synthesize Fe(III) complex, which was further used to catalyze the oxidation of methanol using molecular oxygen as oxidant. Both the cross linked polymeric ligand and its complex were characterized using FT-IR, UV-visible and Atomic Absorption Spectroscopic methods as well as Scanning Electron Spectroscopy (SEM). Diacetylnaphtalene-2,7-diol cross linked chitosan showed an appreciable shift in O-H and N-H stretches around 3574cm-1 and 3227cm-1 while a new band attributed to imine –C=N stretching vibration appeared at 1614cm-1. The bending vibrations between 1000 cm-1 and 420 cm-1 were also observed for the metal complex indicating possible interactions. The UV-Vis spectrum of the ligand exhibited a distinct absorption peak (335 nm) at the range attributed to imine (C=N) n– * transition, which red shifted in the spectrum of the Fe(III) complex. The SEM micrographs of the polymeric ligand and its Fe(III) complex showed significant morphological differences on the surface, which also suggested metal ligand interaction. Application of this new complex for the catalytic oxidation of methanol yielded formaldehyde, confirmed by comparative study of the FT-IR spectra of synthesized formaldehyde and that of industrially produced formaldehyde.