Actinide covalency measured by pulsed electron paramagnetic resonance spectroscopy

Abstract

Our knowledge of actinide chemical bonds lags far behind our understanding of the bonding regimes of any other series of elements. This is a major issue given the technological as well as fundamental importance of f-block elements. Some key chemical differences between actinides and lanthanides-and between different actinides-can be ascribed to minor differences in covalency, that is, the degree to which electrons are shared between the f-block element and coordinated ligands. Yet there are almost no direct measures of such covalency for actinides. Here we report the first pulsed electron paramagnetic resonance spectra of actinide compounds. We apply the hyperfine sublevel correlation technique to quantify the electron-spin density at ligand nuclei (via the weak hyperfine interactions) in molecular thorium(III) and uranium(III) species and therefore the extent of covalency. Such information will be important in developing our understanding of the chemical bonding, and therefore the reactivity, of actinides.

Energy-Degeneracy-Driven Covalency in Actinide Bonding

“…For example, there is a body of evidence that demonstrates -in certain systemssubstantial 5f-and 6d-covalency exists. (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) These data are juxtaposed with numerous studies suggesting that An-ligand bonding is primarily ionic. (21) The later conclusions are fueled by several observables that include (but are not limited to) An-ligand bond distances being routinely predicted using actinide ionic radii and an appreciable body of spectroscopic data that shows the 5f  5f optical transitions are marginally impacted by the ligand field.…”

Molecular single-ion magnets based on lanthanides and actinides: Design considerations and new advances in the context of quantum technologies

“…Combined ESEEM and HYSCORE experiments enabled the measurement of the hyperfine interactions to the 1 H and 13 C nuclei of the Cp ligands, providing information on chemical bonding of the actinide. A larger spin delocalization was found in the uranium compound 94, which explains the faster decoherence compared to 93 [158].…”

“…Coherent Rabi oscillations were observed for all transitions, with the oscillation frequency notably increasing with the microwave power. The authors argued that one of the coherent oscillations observed experimentally is an example [139], [144], [146], [158], [159], [160] [161], [162].…”

Facile Syntheses of pure Uranium(III) Halides: UF3, UCl3, UBr3, and UI3

“…Thanks to the regained popularity of uranium chemistry a variety of remarkable compounds has been discovered in recent years . UI 3 is widely used as a starting material for organometallic uranium chemistry, but usually in the form of its organic solvent adducts, like [UI 3 (THF) 4 ] and the more stable [UI 3 (1,4‐dioxane) 1.5 ] , .…”