MOESSBAUER STUDIES OF SYNTHETIC ANALOGS SIMULATING BUILDING BLOCKS OF NITROGENASE REACTION CENTERS
This project studies the electronic and magnetic properties of Fe-Mo-S complexes and 4Fe-4S clusters towards understanding structure and function of the active centers in the nitrogen fixing enzyme nitrogenase, by means of Moessbauer Spectroscopy and magnetic susceptibility measurements. Two binuclear (Fe-Mo) and two trinuclear (Fe-Mo-Fe and Mo-Fe-Mo) complexes with sulfur bridges between the metal centers have been compared with the electronic structure and magnetic properties of the Fe-Mo cofactor of nitrogenase. The results imply a high electron affinity of the MoS4U24U-4- and intramolecular spin coupling. This and structural similarities with the Fe-Mo cofactor suggest these molecular groups as possible building blocks of the cofactor. 4Fe-4S cubane clusters with mixed terminal ligands have been investigated as possible models for the other major Fe component of nitrogenase, the "P clusters": Extensive charge delocalization is shown to prevail for the 4Fe-4S clusters with mixed monodentate terminal ligands resulting in four indistinguishable Fe sites, whereas clusters with mixed mono- and bidentate terminal ligands display site differentiation among the Fe sites of the cubane similar to that observed for P clusters. These results indicate that the presumed differences in the ligation of P clusters could include expansion to five coordination for the three of the four iron atoms of the cluster.
Bibliographic Reference: EUR 9686 EN (1985) MF, 28 P., BFR 150, BLOW-UP COPY BFR 150, EUROFFICE, LUXEMBOURG, POB 1003
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Record Number: 1989124005500 / Last updated on: 1987-01-01
Available languages: en