Electron-Transfer and Exchange-Interaction Model of the Ligand Hyperfine Structure of Alkylated Iron-Sulfur Clusters.

Iron-sulfur clusters conduct a wide variety of biochemical reactions that are conserved across all domains of life. The detailed quantum spin structure of reactive ligands of these clusters can be studied experimentally and theoretically by means of magnetic hyperfine spectroscopy, which can reveal catalytic intermediates in these biochemical processes. Their theoretical prediction, however, requires either advanced methods that describe strongly correlated systems or Hamiltonian modeling based on symmetry-broken electronic structure methods. This work shows that the addition of electron-transfer interactions to the Heisenberg-Dirac-Van Vleck Hamiltonian model leads to a quantitative explanation of hyperfine coupling constants at active organic ligand sites. Comparison with experimentally available results confirms that our extended approach can be used in calculations aimed at describing cutting-edge systems.