title: Low-energy spectrum of iron-sulfur clusters directly from many-particle quantum mechanics.
abstract: Iron-sulfur clusters are a universal biological motif. They carry out electron transfer, redox chemistry and even oxygen sensing, in diverse processes including nitrogen fixation, respiration and photosynthesis. Their low-lying electronic states are key to their remarkable reactivity, but they cannot be directly observed. Here, we present the first ever quantum calculation of the electronic levels of [2Fe-2S] and [4Fe-4S] clusters free from any model assumptions. Our results highlight the limitations of long-standing models of their electronic structure. In particular, we demonstrate that the widely used Heisenberg double exchange model underestimates the number of states by one to two orders of magnitude, which can conclusively be traced to the absence of Fe dd excitations, thought to be important in these clusters. Furthermore, the electronic energy levels of even the same spin are dense on the scale of vibrational fluctuations and this provides a natural explanation for the ubiquity of these clusters in catalysis in nature.
authors.affiliation: Department of Chemistry, Princeton University, Princeton, New Jersey 08544-1009, USA.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Sharma
authors.affiliation: Max Planck Institute for Chemical Energy Conversion, 45470 Mülheim, Germany.
authors.forename: Kantharuban
authors.initials: K
authors.lastname: Sivalingam
authors.affiliation: Max Planck Institute for Chemical Energy Conversion, 45470 Mülheim, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Neese
authors.affiliation: Department of Chemistry, Princeton University, Princeton, New Jersey 08544-1009, USA.
authors.forename: Garnet Kin-Lic
authors.initials: GK
authors.lastname: Chan
mesh_terms: D002384:Catalysis; D019281:Dimerization; D007501:Iron / Q000737:chemistry*; D008958:Models, Molecular; D011789:Quantum Theory; D013455:Sulfur / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D013455:Sulfur; D007501:Iron