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Variable Denticity in Carboxylate Binding to the Uranyl Coordination Complexes

Tris-carboxylate complexes of uranyl [UO 2] 2+ with acetate and benzoate were generated using electrospray ionization mass spectrometry, and then isolated in a Fourier transform ion cyclotron resonance mass spectrometer. Wavelength-selective infrared multiple photon dissociation (IRMPD) of the tris-...

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Bibliographic Details
Published in:Journal of the American Society for Mass Spectrometry 2010-05, Vol.21 (5), p.719-727
Main Authors: Groenewold, Gary. S., de Jong, Wibe A., Oomens, Jos, Van Stipdonk, Michael J.
Format: Article
Language:English
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Summary:Tris-carboxylate complexes of uranyl [UO 2] 2+ with acetate and benzoate were generated using electrospray ionization mass spectrometry, and then isolated in a Fourier transform ion cyclotron resonance mass spectrometer. Wavelength-selective infrared multiple photon dissociation (IRMPD) of the tris-acetato uranyl anion resulted in a redox elimination of an acetate radical, which was used to generate an IR spectrum that consisted of six prominent absorption bands. These were interpreted with the aid of density functional theory calculations in terms of symmetric and antisymmetric −CO 2 stretches of the monodentate and bidentate acetate, CH 3 bending and umbrella vibrations, and a uranyl O–U–O asymmetric stretch. The comparison of the calculated and measured IR spectra indicated that the predominant conformer of the tris-acetate complex contained two acetate ligands bound in a bidentate fashion, while the third acetate was monodentate. In similar fashion, the tris-benzoate uranyl anion was formed and photodissociated by loss of a benzoate radical, enabling measurement of the infrared spectrum that was in close agreement with that calculated for a structure containing one monodentate and two bidentate benzoate ligands. Infrared multiple photon dissociation spectroscopy shows that uranyl tris-carboxylate complexes have ligands coordinated in both bidentate and monodentate modes.
ISSN:1044-0305
1879-1123
DOI:10.1016/j.jasms.2010.01.021