Copper(II) porphyrin as biomimetic catalyst for oxidation of trimethylphenol

Abstract

Synthetic metalloporphyrins have long been recognized either as functional models or mimics of the cytochrome P-450 enzymes and they are versatile compounds with potential use in drug delivery, catalysis and electronics. In the present study, the metalloporphyrin, (meso-tetra-(p-sulfonatophenyl)- porphyrinato)copper, CuTSPP was synthesized in the reaction between free-base porphyrin, meso-tetra (p-sulfonatophenyl)porphyrin, H2TSPP and copper(II) acetate monohydrate. The materials were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet-Visible (UV-Vis) Spectroscopy, Proton Nuclear Magnetic Resonance (1H NMR) Spectroscopy and Mass Spectrometry (MS) analysis. The FTIR spectra of both free-base porphyrin and CuTSPP showed the appearance of three pronounced bands indicating the presence of the salt form (R-SO3Na) of the sulfonic acid group. Characterization of CuTSPP by UV-Vis spectroscopy confirmed that the insertion of copper into the free-base porphyrin was successful by the appearance of the Soret band and Q bands. The catalytic activity of CuTSPP was tested in the oxidation of 2,3,6-trimethylphenol (TMP) at 60 °C using hydrogen peroxide (H2O2) as oxidant. The reaction parameters including the reaction temperature and time have been optimized. The only product obtained by means of TMP oxidation with H2O2 using CuTSSP is 2,3,5-trimethylbenzoquinone (TMBQ), an important precursor for the industrial production of Vitamin E.