Datensatz

Zusammenfassung

Activation of hydrogen is a topic of great interest, particularly in the context of developing new, environmentally-friendly fuels. Historically, catalysts capable of hydrogen activation or production required heavy and/or expensive transition metals. In nature, however, some bacteria use hydrogen as a fuel source by means of hydrogenases, which are based on inexpensive and more abundant transition metals. The most prevalent class of these enzymes contain a [NiFe] active site. While numerous studies have been aimed towards the characterization of this enzyme and its reaction mechanism, a number of questions remain, particularly concerning are the EPR-silent catalytic intermediates. Herein, we propose the use of nickel valence-to-core X-ray emission spectroscopy (Ni V2C XES) as a experimental technique to study key hydrogenase intermediates. Previously, we have identified spectral signatures of single C, N, and O atoms within large clusters and proteins, that reflects their respective 2s and 2p ionization potentials; this work ultimately lead to the identification of the central light atom of FeMo-co in nitrogenase. In this work, the technique is further extended towards identification of hydrides and protons. We use Ni V2C XES to identify spectral differences which report on the presence (or absence) of a bridging hydride in certain intermediates. The development and application of Ni V2C XES to catalytically-active [NiFe] hydrogenase model compounds (A and B in Figure 1), each containing critical structural motifs relevant to the enzyme, is discussed. The results on other model complexes as well as the implications of these results for studies in the protein and its reaction intermediates will be also addressed.