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

Electrospray ionization (ESI) can produce a wide range of gas-phase uranyl (UO ₂ ²⁺ ) complexes for tandem mass spectrometry studies of intrinsic structure and reactivity. We describe here the formation and collision-induced dissociation (CID) of [UO ₂ (NO ₃ ) ₃ ] ^- and [UO ₂ (NO ₃ ) ₂ (O ₂ )] ^- . Multiple-stage CID experiments reveal that the complexes dissociate in reactions that involve elimination of O ₂ , NO ₂ , or NO ₃ , and subsequent reactions of interesting uranyl-oxo product ions with (neutral) H ₂ O and/or O ₂ were investigated. Density functional theory (DFT) calculations reproduce experimental results and show that dissociation of nitrate ligands, with ejection of neutral NO ₂ , is favored for both [UO ₂ (NO ₃ ) ₃ ] ^- and [UO ₂ (NO ₃ ) ₂ (O ₂ )] ^- . DFT calculations also suggest that H ₂ O adducts to products such as [UO ₂ (O)(NO ₃ )] ^- spontaneously rearrange to create dihydroxides and that addition of O ₂ is favored over addition of H ₂ O to formally U(V) species.
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