Redox Communication within Multinuclear Iron-Sulfur Complexes Related to Electronic Interplay in the Active Site of [FeFe]Hydrogenase

摘要

The one-electron oxidations of a Fe-2 complex lead to the formation of a persistent metal-stabilized thiyl radical Fe-2 species, mixed-valent Fe-4, and Fe-8 complexes. The unpaired spin in the Fe-2 radical species delocalizes over the Fe-2 and the aromatic dithiolate, mostly on the terminal sulfur. The subsequent dimerization of the singly oxidized Fe-2 to the Fe-4 retains the partial thiyl radical character. For an analogue with less steric hindrance, the p-p stacking interaction between the dithiolato aromatic rings induces generation of the Fe-8, in which process electronic structures of the species are modulated through reducing the thiyl radical to the thiolate. Electronic reorganization repeats when the Fe-8 is converted to Fe-4. Electronic interplay in the complexes decreases the energy gap of frontier MOs and buffers electronic impacts upon redox events. Easier accessible redox potentials and increased stability of the species are facilitated. The results demonstrate that electronic versatility of the benzene-dithiolate exerts pronounced influences on electronic and coordination structure of the metal complexes.