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DOE OSTI2021

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

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 report results for the ground and low-lying electronically excited states of the complex [Fe(SCH3)4]2-/1-/2+/3+, using Multi-Reference (CASSCF, MRCISD), and Coupled Cluster [CCSD(T)] methodology in order to provide accurate adiabatic reduction energies, dissociation energies and insights into the bonding analysis. 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 IP of Fe2+. The ionic vs covalent bond character influences the Fe-S bond strength and length, i.e., 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 (FeIII) eV at the RCCSD(T) level of theory.

Tzeli, Demeter↗

DOE OSTI2020

Materials Data on ScH3 by Materials Project

ScH3 is alpha bismuth trifluoride structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Sc3+ sites. In the first Sc3+ site, Sc3+ is bonded in a distorted body-centered cubic geometry to fourteen H1- atoms. There are a spread of Sc–H bond distances ranging from 2.06–2.46 Å. In the second Sc3+ site, Sc3+ is bonded in a distorted body-centered cubic geometry to fourteen H1- atoms. There are a spread of Sc–H bond distances ranging from 2.06–2.46 Å. There are two inequivalent H1- sites. In the first H1- site, H1- is bonded to four Sc3+ atoms to form HSc4 tetrahedra that share corners with twelve equivalent HSc6 octahedra, corners with sixteen equivalent HSc4 tetrahedra, edges with six equivalent HSc4 tetrahedra, and faces with four equivalent HSc6 octahedra. The corner-sharing octahedra tilt angles range from 53–55°. In the second H1- site, H1- is bonded to six Sc3+ atoms to form HSc6 octahedra that share corners with six equivalent HSc6 octahedra, corners with twenty-four equivalent HSc4 tetrahedra, edges with twelve equivalent HSc6 octahedra, and faces with eight equivalent HSc4 tetrahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗