Electronic properties of porphyrins with catalytic activity: a study by X-ray Absorption Spectroscopy

Abstract

Proteins containing metals in the active center are commons in biology, being responsible for innumerous biological processes. Lately, scientists have been looking for inspiration in nature for the development of materials with special properties and more efficient catalysts. One important example of catalysts inspired in biological systems is the porphyrin system. Porphyrins are part of a class of compounds that are appropriate for the comparative studies between structure and function since they are at the same time simple, robust and very similar to proteins containing the heme group, e.g., hemoglobin.In a way to establish a better understanding of the electronic structure and its possible correlations with the catalytic activity of metaloporphyrins, we propose a study utilizing x-ray absorption spectroscopy. The analysis of the spectra using multiple scattering theory or the finite difference method will make possible the investigation of the interaction between the central atom and the ligands. In principle, two state-of-the-art programs will be used to simulate the spectra - FEFF9 and FDMNES. Different theoretical models for the molecular potential, inelastic losses, core-hole effects, etc will be tested in model compounds. Compounds containing iron in varied oxidation states (FeII and FeIII) and different geometries will be used to this purpose. Once an appropriate combination of parameters is obtained, the spectrum of the iron porphyrin FeTTP will be simulated and analyzed in a quantitative manner.