Mimicking the active centres in iron-sulfur proteins: reaction kinetic study of the catalytic behavior and and the redox activity of free FexSy-clusters in an ion trap

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Small iron-sulfur (FeS-)clusters are often considered as the active centers of the most commonly naturally occurring proteins (FeS-proteins) and are thus of fundamental importance for all living organisms. Besides their function as electron transfer medium in biochemical redox reactions, FeS-clusters are especially important as biocatalysts in numerous pivotal processes. In particular, the mild reaction conditions and the ability of such biocatalysts to activate components of the air makes them ideal materials for a "green" i.e. environmentally friendly and sustainable catalysis. Thus, the investigation of the catalytic mechanisms in enzyme reactions is not only of particular importance for a basic understanding of the functionality of life; enzymes as biocatalysts rather represent ideal systems to learn from nature and to use this knowledge industrially for the development of new catalytically active and selective materials. The detailed understanding of the processes is, however, considerably hampered by the very complex structure of FeS-proteins and the influence of their organic environment. For a detailed understanding of the elementary processes on a molecular level it is mandatory to isolate the active centers of the proteins and to study their intrinsic properties independent of their environment. In this context, we will mimic the active centers of FeS-proteins in form of gasphase clusters and will study their redox activity and catalytic properties in different model reactions in an ion trap experiment. The aim of this experimental approach is the elucidation of elementary reaction steps and their dynamics as well as the understanding of basic mechanisms involved in bond activation and bond formation processes and the corresponding charge transfer processes on a strictly molecular level.Particular emphasis will be on the investigation of the reactivity with respect to the activation of fuels (for application in fuel cells), the hydrogen evolution, the ammonia synthesis as well as the effective and selective oxidation of aliphatic and aromatic hydrocarbons. For these systems we will perform reaction kinetic, reaction dynamic and structure determination experiments as a function of cluster size, and cluster composition to identify the most active clusters. Further optimization of the cluster properties will be achieved by changing the charge state of the clusters as well as by substitution of Fe atoms with Mo, V, or Ni atoms.