Collision‐induced dissociation of [UO 2 (NO 3 )(O 2 )] − and reactions of product ions with H 2 O and O 2

We recently reported a detailed investigation of the collision‐induced dissociation (CID) of [UO 2 (NO 3 ) 3 ] − and [UO 2 (NO 3 ) 2 (O 2 )] − in a linear ion trap mass spectrometer ( J. Mass Spectrom . DOI:10.1002/jms.4705). Here, we describe the CID of [UO 2 (NO 3 )(O 2 )] − which is created directly by ESI, or indirectly by simple elimination of O 2 from [UO 2 (NO 3 )(O 2 ) 2 ] − . CID of [UO 2 (NO 3 )(O 2 )] − creates product ions as at m/z 332 and m/z 318. The former may be formed directly by elimination of O 2 , while the latter required decomposition of a nitrate ligand and elimination of NO 2 . DFT calculations identify a pathway by which both product ions can be generated, which involves initial isomerization of [UO 2 (NO 3 )(O 2 )] − to create [UO 2 (O)(NO 2 )(O 2 )] − , from which elimination of NO 2 or O 2 will leave [UO 2 (O)(O 2 )] − or [UO 2 (O)(NO 2 )] − , respectively. For the latter product ion, the composition assignment of [UO 2 (O)(NO 2 )] − rather than [UO 2 (NO 3 )] − is supported by ion‐molecule reaction behavior, and in particular, the fact that spontaneous addition of O 2 , which is predicted to be the dominant reaction pathway for [UO 2 (NO 3 )] − is not observed. Instead, the species reacts with H 2 O, which is predicted to be the favored pathway for [UO 2 (O)(NO 2 )] − . 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 [UO 2 (O)(NO 2 )] − and [UO 2 (O)(O 2 )] − form H 2 O adducts, and calculations suggest these species spontaneously rearrange to create dihydroxides.