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Quantitative Account of the Bonding Properties of a Rubredoxin Model Complex [Fe(SCH3)4]q, q = -2, -1, +2, +3

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Quantitative Account of the Bonding Properties of a Rubredoxin Model Complex [Fe(SCH3)4]q, q = -2, -1, +2, +3
Xantheas, Sotiris S
Τζέλη, Δήμητρα
Raugei, Simone
Άρθρο σε επιστημονικό περιοδικό
2021-10-12
Iron-sulfur clusters play important roles in biology as parts of electron-transfer chains and catalytic cofactors. Here, we report a detailed computational analysis of a structural model of the simplest natural iron-sulfur cluster of rubredoxin and its cationic counterparts. Specifically, we investigated adiabatic reduction energies, dissociation energies, and bonding properties of the low-lying electronic states of the complexes [Fe(SCH3)4]2-/1-/2+/3+ using multireference (CASSCF, MRCISD), and coupled cluster [CCSD(T)] methodologies. We show that the nature of the Fe-S chemical bond and the magnitude of the ionization potentials in the anionic and cationic [Fe(SCH3)4] complexes offer a physical rationale for the relative stabilization, structure, and speciation of these complexes. Anionic and cationic complexes present different types of chemical bonds: prevalently ionic in [Fe(SCH3)4]2-/1- complexes and covalent in [Fe(SCH3)4]2+/3+ complexes. The ionic bonds result in an energy gain for the transition [Fe(SCH3)4]2- → [Fe(SCH3)4]- (i.e., FeII → FeIII) of 1.5 eV, while the covalent bonds result in an energy loss for the transition [Fe(SCH3)4]2+ → [Fe(SCH3)4]3+ of 16.6 eV, almost half of the ionization potential of Fe2+. The ionic versus covalent bond character influences the Fe-S bond strength and length, that is, ionic Fe-S bonds are longer than covalent ones by about 0.2 Å (for FeII) and 0.04 Å (for FeII). Finally, the average Fe-S heterolytic bond strength is 6.7 eV (FeII) and 14.6 eV (FeIII) at the RCCSD(T) level of theory.
Φυσική και θεωρητική χημεία (EL)
Physical and theoretical chemistry (EN)
Chemical calculations (EN)
Electronic structure (EN)
Redox reactions (EN)
Cluster chemistry (EN)
Basis sets (EN)
English
Journal of Chemical Theory and Computation
© 2021 American Chemical Society
National Hellenic Research Foundation (NHRF)
Helios - Repository of the National Hellenic Research Foundation (NHRF)



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