We recently reported a detailed investigation of the collision‐induced dissociation (CID) of [UO2(NO3)3]−and [UO2(NO3)2(O2)]−in a linear ion trap mass spectrometer (
Actinides are inherently radioactive; thus, ionizing radiation is emitted by these elements can have profound effects on its surrounding chemical environment through the formation of free radical species. While previous work has noted that the presence of free radicals in the system impacts the redox state of the actinides, there is little atomistic understanding of how these metal cations interact with free radicals. Herein, we explore the effects of radiation (UV and γ) on three U(VI) trinitrate complexes, M[UO2(NO3)3] (where M=K+, Rb+, Cs+), and their respective nitrate salts in the solid state via electron paramagnetic resonance (EPR) and Raman spectroscopy paired with Density Functional Theory (DFT) methods. We find that the alkali salts form nitrate radicals under UV and γ irradiation, but also note the presence of additional degradation products. M[UO2(NO3)3] solids also form nitrate radicals and additional DFT calculations indicate the species corresponds to a change from the bidentate bound nitrate anion into a monodentate NO3•radical. Computational studies also highlight the need to include the second sphere coordination environment around the [UO2(NO3)3]0,1species to gain agreement between the experimental and predicted EPR signatures.
more » « less- PAR ID:
- 10511174
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 30
- Issue:
- 35
- ISSN:
- 0947-6539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract J. Mass Spectrom . DOI:10.1002/jms.4705). Here, we describe the CID of [UO2(NO3)(O2)]−which is created directly by ESI, or indirectly by simple elimination of O2from [UO2(NO3)(O2)2]−. CID of [UO2(NO3)(O2)]−creates product ions as atm/z 332 andm/z 318. The former may be formed directly by elimination of O2, while the latter required decomposition of a nitrate ligand and elimination of NO2. DFT calculations identify a pathway by which both product ions can be generated, which involves initial isomerization of [UO2(NO3)(O2)]−to create [UO2(O)(NO2)(O2)]−, from which elimination of NO2or O2will leave [UO2(O)(O2)]−or [UO2(O)(NO2)]−, respectively. For the latter product ion, the composition assignment of [UO2(O)(NO2)]−rather than [UO2(NO3)]−is supported by ion‐molecule reaction behavior, and in particular, the fact that spontaneous addition of O2, which is predicted to be the dominant reaction pathway for [UO2(NO3)]−is not observed. Instead, the species reacts with H2O, which is predicted to be the favored pathway for [UO2(O)(NO2)]−. This result in particular demonstrates the utility of ion‐molecule reactions to assist the determination of ion composition. As in our earlier study, we find that ions such as [UO2(O)(NO2)]−and [UO2(O)(O2)]−form H2O adducts, and calculations suggest these species spontaneously rearrange to create dihydroxides. -
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