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  Magnetic exchange and valence delocalization in a mixed valence [Fe2+Fe3+Te2]+ complex: insights from theory and interpretations of magnetic and spectroscopic data

Atanasov, M., Spiller, N., & Neese, F. (2022). Magnetic exchange and valence delocalization in a mixed valence [Fe2+Fe3+Te2]+ complex: insights from theory and interpretations of magnetic and spectroscopic data. Physical Chemistry Chemical Physics, 24(35), 20760-20775. doi:10.1039/D2CP02975H.

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Atanasov, Mihail1, 2, Author           
Spiller, Nico3, Author           
Neese, Frank3, Author           
1Research Group Atanasov, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_2541704              
2Institute of General and Inorganic Chemistry, Bulgarian Academy of Science, Akad-Georgi Bontchev Str. Bl.11, 1113-Sofia, Bulgaria, ou_persistent22              
3Research Department Neese, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_2541710              


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 Abstract: A mixed valence binuclear Fe2.5+–Fe2.5+ (Robin–Day Class III) transition metal complex, [Fe2.5+μTe2Fe2.5+]1−, composed of two FeN2Te2 pseudo-tetrahedral units with μ-bridging Te2− ligands was reported to exist in an unprecedented S = 3/2 ground state (Nature Chemistry, https://doi.org/10.1038/s41557-021-00853-5). For this and the homologous complexes containing Se2− and S2−, the Anderson-Hasegawa double exchange spin-Hamiltonian was broadly used to interpret the corresponding structural, spectroscopic and magnetic data. First principles multireference ab initio calculations are used here to simulate magnetic and spectroscopic EPR data; analysis of the results affords a rationale for the stabilization of the S = 3/2 ground state of the Fe2 pair. Complete Active Space Self-Consistent Field (CASSCF) calculations and dynamical correlation accounted for by means of N-Electron Valence Perturbation Theory to Second Order (NEVPT2) reproduce well the g-factors determined from simulations of X-band EPR spectra. A crucial technical tool to achieve these results is: (i) use of a localized orbital formulation of the many-particle problem at the scalar-relativistic CASSCF step; (ii) choice of state averaging over states of a given spin (at the CASCI/NEVPT2 step); and (iii) accounting for spin–orbit coupling within the non-relativistic Born–Oppenheimer (BO) many-particle basis using Quasi-Degenerate Perturbation Theory (QDPT). The inclusion of the S = 5/2 spin manifold reproduced the observed increase in the magnetic susceptibility (χT) in the high temperature range (T > 100 K), which is explained by thermal population of the S = 5/2 excited state at energy 160 cm−1 above the S = 3/2 ground state. Theoretical values of χT from experimentally reported data points in the temperature range from 3 to 30 K were further computed and analyzed using a model which takes spin–phonon coupling into account. The model considerations and the computational protocols of this study are generally applicable to any Class I/II mixed valence dimer. The work can potentially stimulate further experimental and theoretical work on bi- and oligonuclear transition metal complexes of importance to bioinorganic chemistry and life sciences.


Language(s): eng - English
 Dates: 2022-06-302022-08-222022-09-21
 Publication Status: Published in print
 Pages: 16
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1039/D2CP02975H
 Degree: -



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Title: Physical Chemistry Chemical Physics
  Abbreviation : Phys. Chem. Chem. Phys.
Source Genre: Journal
Publ. Info: Cambridge, England : Royal Society of Chemistry
Pages: - Volume / Issue: 24 (35) Sequence Number: - Start / End Page: 20760 - 20775 Identifier: ISSN: 1463-9076
CoNE: https://pure.mpg.de/cone/journals/resource/954925272413_1