Electronic structure, surface reactivity and site analysis of transition metal complexes and metalloproteins by X-ray photoelectron spectroscopy

摘要

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.High resolution x-ray photoelectron core level spectra for a variety of transition metal complexes and metalloproteins are presented and related to questions of surface reactivity, electronic structure and metal ion valency. Core level spectra of VOSO4, VB2, V2O3, V2O5, V, VN, Na3VO4, B2O3, B, H3BO3, [...], Au, Laccase, Stellacyanin, Plastocyanin, Hemocyanin, Spinach Ferredoxin, High Potential Iron Protein, [...], [...], [...], [...], [...], [...], [...], [...], [...], [...] are reported.Electron binding energies correlated by internal referencing are tabulated for the species studied.Charging effects in insulating chemical species are quantified and used to examine the electronic and chemical properties of the compounds studied. It is demonstrated that charge neutralization in electron spectroscopy is primarily due to capture of secondary electrons in the sample chamber with average kinetic energies below 6 eV.Data handling methods for noise removal based on Fourier methods are presented. Treatment of the observed photoelectron line shape is given and spectral deconvolution is employed in data analysis.Passivation reactions on vanadium diboride in carboxylic acid attack are attributed to the formation of surface vanadium oxides. Quantitative aspects of the electron spectra are developed, together with observed charging phenomenon, to show the unperturbed observation of adsorbed species on catalytic vanadium oxides.The valency of copper in Laccase is studied by means of new copper sulfo-complexes and the well-defined proteins Stellacyanin and Plastocyanin. Type 1 and Type 2 copper is observed and Type 3 copper is described by a [...] model. Oxyhemocyanin is also studied and assigned in terms of a cupric model.The [...] cluster complex is examined and the mercaptyl and sulfido sulfurs are assigned. Only one iron state is observed, [...], supporting the delocalized model of this species. It is suggested that the oxidized and reduced cluster species can be stabilized in the electron spectrometer. By comparison of the photoelectron spectra, the cluster complex is shown to be a reasonable model for 2-Fe and 4-Fe Ferredoxins and a discussion of the spectral differences is given.The experimental parameters necessary for the successful study of metalloproteins by photoelectron spectroscopy are developed in terms of elemental sensitivity, decomposition profiling, photoreduction, energy reference standards, sample preparation and thermal effects.