Photoelectron spectroscopy and the electronic structure of the uranyl tetrachloride dianion: UO2Cl42−

Abstract

The uranyl tetrachloride dianion (UO(2)Cl(4)(2-)) is observed in the gas phase using electrospray ionization and investigated by photoelectron spectroscopy and relativistic quantum chemical calculations. Photoelectron spectra of UO(2)Cl(4)(2-) are obtained at various photon energies and congested spectral features are observed. The free UO(2)Cl(4)(2-) dianion is found to be highly stable with an adiabatic electron binding energy of 2.40 eV. Ab initio calculations are carried out and used to interpret the photoelectron spectra and elucidate the electronic structure of UO(2)Cl(4)(2-). The calculations show that the frontier molecular orbitals in UO(2)Cl(4)(2-) are dominated by the ligand Cl 3p orbitals, while the U-O bonding orbitals are much more stable. The electronic structure of UO(2)Cl(4)(2-) is compared with that of the recently reported UO(2)F(4)(2-) [P. D. Dau, J. Su, H. T. Liu, J. B. Liu, D. L. Huang, J. Li, and L. S. Wang, Chem. Sci. 3 1137 (2012)]. The electron binding energy of UO(2)Cl(4)(2-) is found to be 1.3 eV greater than that of UO(2)F(4)(2-). The differences in the electronic stability and electronic structure between UO(2)Cl(4)(2-) and UO(2)F(4)(2-) are discussed.

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

“…The diagonal matrix elements were replaced by the individual CCSD(T) or CR-EOM-CCSD(T) or CASPT2 state energies at the SR level, which are denoted as CASSCF/CCSD(T)/SO or CASSCF/CR-EOM-CCSD(T)/SO or CASSCF/CASPT2/SO methods, respectively. [25][26][27][56][57][58][59][60] In the CASSCF/CR-EOM-CCSD(T)/SO calculation for UCl 6 − , the CCSD(T) groundstate energy and the CR-EOM-CCSD(T) 5f 1 excited state energies were used as diagonal matrix elements of the SO coupling matrix. That is, the vertical excitation energies of UCl 6 2− and UCl 6 − at the SO level were calculated with the socalled CASSCF/CAS(2,7)PT2/SO and CASSCF/CR-EOM-CCSD(T)/SO methods, respectively.…”

“…24 Relevant to the current uranium halides, we have successfully applied ESI-PES to probe the electronic structures of a series of uranyl and uranium halide anions in conjunction with relativistic quantum chemical calculations. [25][26][27][28][29][30][31] In particular, we have produced [UF 5 ] − and [UF 6 ] − using ESI and obtained the PES spectra of [UF 5 ] − both at room temperature and low temperature, which yielded an accurate electron affinity (EA) for UF 5 as 3.885 ± 0.015 eV. 28,29 The [U(f 2 )F 5 ] − anion has a C 4v symmetry with two unpaired 5f electrons, occupying f z 3 and f xyz type orbitals, respectively.…”

Gas Phase Reactions of Ions Derived from Anionic Uranyl Formate and Uranyl Acetate Complexes

“…Electrospray ionization (ESI) provides easy access to a wide range of gasphase complexes containing uranium in high oxidation states (+5 and +6) for studies of intrinsic structure and reactivity (i.e., outside of the influence of solvent or other condensed phase effects) in a species specific fashion. For example, the transfer of uranium as mono-positive, pentavalent U V O 2 + from solution to the gas phase using ESI was first reported in 1992 [5] and since then, advances in the fundamental understanding of uranyl coordination chemistry have been made using the ionization method [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Most importantly, ESI has been used to generate gas-phase, doubly charged complexes containing UO 2…”

Communication: Observation of dipole-bound state and high-resolution photoelectron imaging of cold acetate anions

“…This apparatus is an improved version based on our original ESI-PES system that consisted of a roomtemperature ion trap and a magnetic-bottle PES analyzer. [42][43][44][45] One advantage of PE imaging is the PAD, which provides information about the nature of the occupied molecular orbital from which the electron is ejected. 46,47 The acetate anions were generated by electrospray of 1 mM solution of CH 3 COONa dissolved in a mixed CH 3 OH/H 2 O solvent (9:1 volume ratio).…”