| Autor: |
Stoian SA; Department of Chemistry, University of Idaho, Moscow, Idaho 83844, United States., Moshari M; Department of Chemistry, University of Idaho, Moscow, Idaho 83844, United States., Ferentinos E; Inorganic Chemistry Laboratory, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Zografou, 15771 Athens, Greece., Grigoropoulos A; Inorganic Chemistry Laboratory, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Zografou, 15771 Athens, Greece., Krzystek J; National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States., Telser J; Department of Biological, Physical, and Health Sciences, Roosevelt University, Chicago, Illinois 60605, United States., Kyritsis P; Inorganic Chemistry Laboratory, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Zografou, 15771 Athens, Greece. |
| Abstrakt: |
In this work, we assessed the electronic structures of two pseudotetrahedral complexes of Fe II , [Fe{(SP i Pr 2 ) 2 N} 2 ] (1 ) and [Fe{(SeP i Pr 2 ) 2 N} 2 ] ( 2 ), using high-frequency and -field EPR (HFEPR) and field-dependent 57 Fe Mössbauer spectroscopies. This investigation revealed S = 2 ground states characterized by moderate, negative zero-field splitting (zfs) parameters D . The crystal-field (CF) theory analysis of the spin Hamiltonian (sH) and hyperfine structure parameters revealed that the orbital ground states of 1 and 2 have a predominant d x 2 - y 2 character, which is admixed with d z 2 (∼10%). Although replacing the S-containing ligands of 1 by their Se-containing analogues in 2 leads to a smaller | D | value, our theoretical analysis, which relied on extensive ab initio CASSCF calculations, suggests that the ligand spin-orbit coupling (SOC) plays a marginal role in determining the magnetic anisotropy of these compounds. Instead, the d x 2 - y 2 β → d xy β excitations yield a large negative contribution, which dominates the zfs of both 1 and 2 , while the different energies of the d x 2 - y 2 β → d xz β transitions are the predominant factor responsible for the difference in zfs between 1 and 2 . The electronic structures of these compounds are contrasted with those of other [FeS 4 ] sites, including reduced rubredoxin by considering a D 2 -type distortion of the [Fe(E-X) 4 ] cores, where E = S, Se; X = C, P. Our combined CASSCF/DFT calculations indicate that while the character of the orbital ground state and the quintet excited states' contribution to the zfs of 1 and 2 are modulated by the magnitude of the D 2 distortion, this structural change does not impact the contribution of the excited triplet states. |
