Photoelectron spectroscopy and theoretical studies of gaseous uranium hexachlorides in different oxidation states: UCl6q− (q = 0–2)

Abstract

Uranium chlorides are important in actinide chemistry and nuclear industries, but their chemical bonding and many physical and chemical properties are not well understood yet. Here, we report the first experimental observation of two gaseous uranium hexachloride anions, UCl6 (-) and UCl6 (2-), which are probed by photoelectron spectroscopy in conjunction with quantum chemistry calculations. The electron affinity of UCl6 is measured for the first time as +5.3 eV; its second electron affinity is measured to be +0.60 eV from the photoelectron spectra of UCl6 (2-). We observe that the detachment cross sections of the 5f electrons are extremely weak in the visible and UV energy ranges. It is found that the one-electron one-determinental molecular orbital picture and Koopmans' theorem break down for the strongly internally correlated U-5f(2) valence shell of tetravalent U(+4) in UCl6 (2-). The calculated adiabatic and vertical electron detachment energies from ab initio calculations agree well with the experimental observations. Electronic structure and chemical bonding in the uranium hexachloride species UCl6 (2-) to UCl6 are discussed as a function of the oxidation state of U.

Monovalent lanthanide(I) in borozene complexes

“…2 a and c ). The structures and photoelectron spectra of PrB 8 − and LaB 8 − are nearly identical, because of the nonbonding nature of the highly contracted 4 f orbitals and the low detachment cross-sections of f -electrons 41 , 44 , 46 – 49 . Thus, we will only discuss LaB 8 − in detail as a representative of the early-lanthanide octa-boron clusters.…”

Periodic Trends in Actinyl Thio-Crown Ether Complexes

“…Actinyl complexes normally coordinate 4-6 monodentate ligands in their equatorial plane. [20][21][22][23][24] The f-elements, in contrast to many d-block transition metals, are in general hard acids and therefore have a strong affinity for hard O-and F-donor ligands. The choice of donor atoms has been a hot topic in the rational design of actinide separation or sequestering ligands.…”

Anomalous magnetism of uranium(IV)-oxo and -imido complexes reveals unusual doubly degenerate electronic ground states

“…9,10 For O h -symmetric [UX 6 ] 2À , such a behavior is known 5,11,12 and occurs because the J = 4 spin-orbit multiplet splits into A 1 , E, T 1 , and T 2 irreducible representations in O h symmetry, 11 for which the A 1 singlet state is lowest in energy. 12,13 The A 1 state is diamagnetic because it is composed of approximately 58% m J = 0, 21% m J = À4, and 21% m J = +4, 12 where the m J = 0 state is itself diamagnetic and the equal contributions of the m J = G4 states cancel out each other; this can also be mapped to spin and orbital contributions to the m J states, which can be calculated using Clebsch-Gordan coefficients 14 and can be measured experimentally. 15 On the other hand, compounds of different symmetry may not show a decrease to near-zero magnetic moment at low temperatures, signifying the presence of a degenerate paramagnetic ground state (E).…”