Cation-Cation Interactions in [(UO2)2(OH)n](4-n) Complexes

Journal Article · Mon Oct 07 04:00:00 EDT 2013 · Inorganic Chemistry, 52(19):11269-11279

DOI:https://doi.org/10.1021/ic4015338· OSTI ID:1114895

Odoh, Samuel O.; Govind, Niranjan; Schreckenbach, Georg; De Jong, Wibe A.

The structures and bonding of gas-phase [(UO2)2(OH)n]4-n (n=2-6) complexes have been studied using density functional theory (DFT), MP2 and CCSD(T) methods with particular emphasis on ground state structures featuring cation-cation interactions (CCIs) between the uranyl groups. An interesting trend is observed in the stabilities of members of this series of complexes. The structures of [(UO2)2(OH)2]2+, [(UO2)2(OH)4] and [(UO2)2(OH)6]2- featuring CCIs are found at higher energies (by 3-20 kcal/mol) in comparison to their conventional μ2-dihydroxo structures. In contrast, the CCI structures of [(UO2)2(OH)3]+ and [(UO2)2(OH)5]- are respectively almost degenerate with and lower in energy than the structures with the μ2-dihydroxo format. The origin of this trend lies in the ‘symmetry’-based need to balance the coordination numbers and effective atomic charges of each uranium center. The calculated IR vibrational frequencies provide signature probes that can be used in differentiating the lowenergy structures and in experimentally confirming the existence of the structures featuring CCIs. Analysis of the bonding in the structures of [(UO2)2(OH)3]+ and [(UO2)2(OH)5]- shows that the CCIs and bridging hydroxo between the dioxo-uranium units are mainly electrostatic in nature.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1114895
• Report Number(s): PNNL-SA-96382; 44669; KC0302030
• Journal Information: Inorganic Chemistry, 52(19):11269-11279, Journal Name: Inorganic Chemistry, 52(19):11269-11279
• Country of Publication: United States
• Language: English

Related Subjects

Complexes
Density Functional Theory
DFT
Environmental Molecular Sciences Laboratory
MP2
Moller Plesset
CCSD(T)
Coupled Cluster