Probing the structural effects on the intrinsic electronic and redox properties of [2Fe-2S]+ clusters, a broken-symmetry density functional theory study

In biological electron transport chains, [2Fe-2S] clusters have versatile electrochemical properties and serve as important electron carriers in a wide variety of biological processes. To understand structural effects on the variation in reduction potentials in [2Fe-2S] proteins, a series of [2Fe-2S] protein analogs with bidentate ligands (-SC2H4NH2) were recently produced by collision-induced dissociation of [Fe4S4(L)(4)](2-) (L = SC (2) H (4) NH (2)). Combined with photoelectron spectroscopy findings, the reaction mechanisms of [Fe (4) S (4)(L)(4)](2-) to [Fe (2) S (2)(L)(2)](-) and the structural effects of ligands on the electronic and redox properties of the [2Fe-2S] clusters are investigated here using broken-symmetry density functional theory method. Our calculations suggest that [Fe2S2(eta(2)-L)(cis-L)](-) and [Fe2S2(eta(2)-L)(2)](-) are the experimentally observed [2Fe-2S] products, which are generated via a fission process of [Fe (4) S (4)(L)(4)](2-) followed by rearrangement of ligands of [Fe (2) S (2)(L)(2)](-). Moreover, structural variation of the ferrous center may dramatically affect the oxidation energy of the [2Fe-2S] clusters.