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Title: The roles of 4f- and 5f-orbitals in bonding: A magnetochemical, crystal field, density functional theory, and multi-reference wavefunction study

The electronic structures of 4f 3/5f 3 Cp" 3M and Cp" 3M·alkylisocyanide complexes, where Cp" is 1,3-bis-(trimethylsilyl)cyclopentadienyl, are explored with a focus on the splitting of the f-orbitals, which provides information about the strengths of the metal–ligand interactions. While the f-orbital splitting in many lanthanide complexes has been reported in detail, experimental determination of the f-orbital splitting in actinide complexes remains rare in systems other than halide and oxide compounds, since the experimental approach, crystal field analysis, is generally significantly more difficult for actinide complexes than for lanthanide complexes. In this study, a set of analogous neodymium(III) and uranium(III) tris-cyclopentadienyl complexes and their isocyanide adducts was characterized by electron paramagnetic resonance (EPR) spectroscopy and magnetic susceptibility. The crystal field model was parameterized by combined fitting of EPR and susceptibility data, yielding an accurate description of f-orbital splitting. The isocyanide derivatives were also studied using density functional theory, resulting in f-orbital splitting that is consistent with crystal field fitting, and by multi-reference wavefunction calculations that support the electronic structure analysis derived from the crystal-field calculations. The results highlight that the 5f-orbitals, but not the 4f-orbitals, are significantly involved in bonding to the isocyanide ligands. The main interaction between isocyanide ligand andmore » the metal center is a σ-bond, with additional 5f to π* donation for the uranium complexes. As a result, while interaction with the isocyanide π*-orbitals lowers the energies of the 5f xz2 and 5f yz2-orbitals, spin–orbit coupling greatly reduces the population of 5f xz2 and 5f yz2 in the ground state.« less
Authors:
 [1] ;  [2] ; ORCiD logo [3] ;  [4] ;  [4] ;  [5]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. RWTH Aachen Univ., Aachen (Germany)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  4. Univ. at Buffalo, State Univ. of New York, Buffalo, NY (United States)
  5. RWTH Aachen Univ., Aachen (Germany); Forschungszentrum Julich, Julich (Germany)
Publication Date:
Report Number(s):
LA-UR-15-29482
Journal ID: ISSN 1477-9226; ICHBD9
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Dalton Transactions
Additional Journal Information:
Journal Volume: 45; Journal Issue: 28; Journal ID: ISSN 1477-9226
Publisher:
Royal Society of Chemistry
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1341858