Molecular and Electronic Structures of Eight-Coordinate Uranium Bipyridine Complexes: A Rare Example of a Bipy(2-) Ligand Coordinated to a U4+ Ion - INSA Toulouse - Institut National des Sciences Appliquées de Toulouse Access content directly
Journal Articles Inorganic Chemistry Year : 2017

Molecular and Electronic Structures of Eight-Coordinate Uranium Bipyridine Complexes: A Rare Example of a Bipy(2-) Ligand Coordinated to a U4+ Ion

Abstract

Reaction of trivalent [(((ArO)-Ar-Ad,tBu)(3)tacn)U] (1) with 2,2'-bipyridine (bipy) yields [(((ArO)-Ar-Ad,tBu)(3)tacn)U(bipy)] (2) and subsequent reduction of 2 with KC8 in the presence of Kryptofix222 furnishes [K(2.2.2-crypt)] [ (((ArO)-Ar-Ad,tBu)(3)tacn)U-(bipy)] (3). Alternatively, complex 3 can be synthesized from 1 by addition of [K(bipy)] in the presence of the cryptand. New complexes 2 and 3 are characterized by a variety of spectroscopic, electrochemical, and magnetochemical methods, single-crystal X-ray diffraction, computational methods, and CHN elemental analysis. Structural analyses reveal a bipyridine radical (bipy(center dot-)) ligand in 2 and a dianionic (bipy(2-)) species in 3. Complex 3 represents a rare example of an isolated and unambiguously characterized bipy(2-) ligand coordinated to a uranium ion. The electronic structure assignments are supported by UV/vis/NIR and EPR spectroscopy, as well as SQUID magnetometry. The results of CASSCF calculations indicate multiconfigurational ground states for complexes 2 and 3. The electronic ground state for 2 consists of an open-shell doublet U4+(bipy(center dot-)) state (91%) and a closed-shell doublet U5+(bipy(2-)) state (9%). The almost degenerate multiconfigurational ground state for 3 was found to be composed of an open shell singlet and pure triplet state 0.06 eV higher in energy, both resulting from the U4+(5f(2)) (bipy(2-)) configuration.
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Dates and versions

hal-01961177 , version 1 (19-12-2018)

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  • HAL Id : hal-01961177 , version 1

Cite

Michael W. Rosenzweig, Frank W. Heinemann, Laurent Maron, Karsten Meyer. Molecular and Electronic Structures of Eight-Coordinate Uranium Bipyridine Complexes: A Rare Example of a Bipy(2-) Ligand Coordinated to a U4+ Ion. Inorganic Chemistry, 2017, 56 (5), pp.2792--2800. ⟨hal-01961177⟩
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