Infrared Spectroscopy of Discrete Uranyl Anion Complexes

Journal Article · Sat Dec 01 04:00:00 EST 2007 · Journal of Physical Chemistry A

OSTI ID:923516

Groenewold, Gary S; Gianotto, Anita K; McIlwain, Michael E; Van Stipdonk, Michael J; Kullman, Michael; Cooper, Travis J; Moore, David T; Polfer, Nick; Oomens, Jos; Infante, Ivan; Visscher, Lucas; Siboulet, Bertrand; de Jong, Wibe A

The Free-Electron Laser for Infrared Experiments, FELIX, was used to study the wavelength-resolved multiphoton dissociation of discrete, gas phase uranyl (UO22+) complexes containing a single anionic ligand (A), with or without ligated solvent molecules (S). The apparent uranyl antisymmetric and symmetric stretching frequencies were measured for complexes with general formula [UO2A(S)n]+, where A was either hydroxide, methoxide or acetate, S was water, ammonia, acetone or acetonitrile, and n = 0-2. The values for the antisymmetric stretching frequency for uranyl ligated with only an anion ([UO2A]+) were as low or lower than measurements for [UO2]2+ ligated with as many as five strong neutral donor ligands, and are comparable to solution phase values. This result was surprising because initial DFT calculations using B3LYP predicted values that were 30 – 40 cm-1 higher, consistent with intuition but not with the data. Modification of the basis set and use of alternative functionals improved computational accuracy for the methoxide and acetate complexes, but calculated values for the hydroxide were greater than the measurement regardless of the computational method used. Attachment of a neutral donor ligand S to [UO2A]+ produced [UO2AS]+, which resulted only very modest changes to the uranyl frequency, and did not universally shift values lower. DFT calculations for [UO2AS]+ were in accord with trends in the data, and showed that attachment of the solvent was accommodated by weakening of the U-anion bond as well as the uranyl. When uranyl frequencies were compared for [UO2AS]+ species having different solvent neutrals, values decreased with increasing neutral nucleophilicity.

• Research Organization: Idaho National Laboratory (INL)
• Sponsoring Organization: DOE - SC
• DOE Contract Number: AC07-99ID13727
• OSTI ID: 923516
• Report Number(s): INL/JOU-07-12193
• Journal Information: Journal of Physical Chemistry A, Journal Name: Journal of Physical Chemistry A Journal Issue: 3 Vol. 112
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ACCURACY
ACETATES
ACETONE
ACETONITRILE
AMMONIA
ANIONS
DISSOCIATION
FREE ELECTRON LASERS
FUNCTIONALS
Free-Electron Laser for Infrared Experiments
HYDROXIDES
MODIFICATIONS
SOLVENTS
SPECTROSCOPY
WATER
gas phase uranyl (UO22+) complexes
neutral nucleophilicity