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1. Creation of Gas‐Phase Organo‐Uranium Species by Removal of “yl” Oxo Ligands From UO 2 2+ Carboxylate Precursor Ions

   https://doi.org/10.1002/rcm.9954  

   Lenze, Samuel J. ; Terhorst, Justin ; Ihabi, Amina ; Corcovilos, Theodore ; van_Stipdonk, Michael J. ( December 2024 , Rapid Communications in Mass Spectrometry)

   These experiments were conducted to measure the diversity of organo‐U (IV) and U (III) ions created using multiple‐stage tandem MS and collision‐induced dissociation of halogen‐substituted U^VIO₂‐phenide complexes [UO₂(C₆H₃FX)]⁺, X = Cl, Br, or I.

   Samples of UO₂(O₂C‐C₆H₃FX)₂were prepared by digesting UO₃with appropriate halogen‐substituted carboxylic acids in deionized water. Solutions for ESI were created by diluting the digested sample in 50:50 H₂O/CH₃OH. Precursor ions for multiple‐stage tandem MS were generated by electrospray ionization (ESI). Multiple‐stage collision‐induced dissociation (He collision gas) in a linear quadrupole ion trap mass spectrometer was used to prepare species such as [U^IVFX(C≡CH)]⁺and U^IIIF(C≡CH)]⁺for subsequent study of ion‐molecule reactions with adventitious neutrals in the ion trap.

   Multiple‐stage CID of the [UO₂(C₆H₃FX)]⁺, X = Cl, Br, or I, complexes caused removal of both “yl” oxo ligands from of the UO₂²⁺moiety to create ions such as [U^IVFX(C≡CH)]⁺and [U^IIIFX]⁺. For [U^IVFXC≡CH]⁺and [U^IIIFC≡CH]⁺products, hydrolysis to generate [U^IVFX (OH)]⁺and [U^IIIF (OH)]⁺, with concomitant loss of HC≡CH, was observed. CID of [UO₂(C₆H₃FBr)]⁺and [UO₂(C₆H₃FI)]⁺caused reductive elimination of the respective halogen radicals to generate interesting organo‐U (III) species such as [U^IIIF(C≡CH)]⁺and [U^IIIC₂]⁺.

   The use of “preparative” tandem mass spectrometry and a suite of halogen substituted benzoic acid ligands can be used to remove both oxo ligands of UO₂²⁺and generate a group of homologous organo‐U (IV) and organo‐U (III) ions for studies of intrinsic reactivity.

    

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2. 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

   https://doi.org/10.1002/jms.4705  

   Bubas, Amanda R. ; Perez, Evan ; Metzler, Luke J. ; Rissler, Scott D. ; Van Stipdonk, Michael J. ( February 2021 , Journal of Mass Spectrometry)

   Electrospray ionization (ESI) can produce a wide range of gas‐phase uranyl (UO₂²⁺) complexes for tandem mass spectrometry studies of intrinsic structure and reactivity. We describe here the formation and collision‐induced dissociation (CID) of [UO₂(NO₃)₃]⁻and [UO₂(NO₃)₂(O₂)]⁻. Multiple‐stage CID experiments reveal that the complexes dissociate in reactions that involve elimination of O₂, NO₂, or NO₃, and subsequent reactions of interesting uranyl‐oxo product ions with (neutral) H₂O and/or O₂were investigated. Density functional theory (DFT) calculations reproduce experimental results and show that dissociation of nitrate ligands, with ejection of neutral NO₂, is favored for both [UO₂(NO₃)₃]⁻and [UO₂(NO₃)₂(O₂)]⁻. DFT calculations also suggest that H₂O adducts to products such as [UO₂(O)(NO₃)]⁻spontaneously rearrange to create dihydroxides and that addition of O₂is favored over addition of H₂O to formally U(V) species.

    

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3. Intrinsic reactivity of [OUCH] + : Apparent synthesis of [OUS] + by reaction with CS 2

   https://doi.org/10.1002/rcm.9260  

   Metzler, Luke J. ; Farmen, Christopher T. ; Fry, Allison N. ; Seibert, Mark P. ; Massari, Kayla A. ; Corcovilos, Theodore A. ; van Stipdonk, Michael J. ( February 2022 , Rapid Communications in Mass Spectrometry)

   Building on our report that collision‐induced dissociation (CID) can be used to create the highly reactive U‐alkylidyne species [O=U≡CH]⁺, our goal was to determine whether the species could be as an intermediate for synthesis of [OUS]⁺by reaction with carbon disulfide (CS₂).

   Cationic uranyl‐propiolate precursor ions were generated by electrospray ionization, and multiple‐stage CID in a linear trap instrument was used to prepare [O=U≡CH]⁺. Neutral CS₂was admitted into the trap through a modified He inlet and precision leak valves.

   The [O=U≡CH]⁺ion reacts with CS₂to generate [OUS]⁺. CID of [OUS]⁺causes elimination of the axial sulfide ligand to generate [OU]⁺. Using isotopically labeled reagent, we found that [OUS]⁺reacts with O₂to create [UO₂]⁺.

   [O=U≡CH]⁺proves to be a useful reagent ion for synthesis of [OUS]⁺, a species that to date has only been created by gas‐phase reactions of U⁺and U²⁺. Dissociation of [OUS]⁺to create [OU]⁺, but not [US]⁺, and the efficient conversion of the species into [UO₂]⁺, is consistent with the relative differences in U–O and U–S bond energies.

    

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

   https://doi.org/10.1002/jms.4720  

   Bubas, Amanda R. ; Perez, Evan ; Metzler, Luke J. ; Rissler, Scott D. ; Van Stipdonk, Michael J. ( April 2021 , Journal of Mass Spectrometry)

   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 (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/z332 andm/z318. 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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5. A plethora of isomerization processes and hydrogen scrambling in the fragmentation of the methanol dimer cation: a PEPICO study

   https://doi.org/10.1039/d1cp05155e  

   Wu, Xiangkun ; Zhou, Xiaoguo ; Bjelić, Saša ; Hemberger, Patrick ; Sztáray, Bálint ; Bodi, Andras ( January 2022 , Physical Chemistry Chemical Physics)

   The valence photoionization of light and deuterated methanol dimers was studied by imaging photoelectron photoion coincidence spectroscopy in the 10.00–10.35 eV photon energy range. Methanol clusters were generated in a rich methanol beam in nitrogen after expansion into vacuum. They generally photoionize dissociatively to protonated methanol cluster cations, (CH 3 OH) n H + . However, the stable dimer parent ion (CH 3 OH) 2 + is readily detected below the dissociation threshold to yield the dominant CH 3 OH 2 + fragment ion. In addition to protonated methanol, we could also detect the water- and methyl-loss fragment ions of the methanol dimer cation for the first time. These newly revealed fragmentation channels are slow and cannot compete with protonated methanol cation formation at higher internal energies. In fact, the water- and methyl-loss fragment ions appear together and disappear at a ca. 150 meV higher energy in the breakdown diagram. Experiments with selectively deuterated methanol samples showed H scrambling involving two hydroxyl and one methyl hydrogens prior to protonated methanol formation. These insights guided the potential energy surface exploration to rationalize the dissociative photoionization mechanism. The potential energy surface was further validated by a statistical model including isotope effects to fit the experiment for the light and the perdeuterated methanol dimers simultaneously. The (CH 3 OH) 2 + parent ion dissociates via five parallel channels at low internal energies. The loss of both CH 2 OH and CH 3 O neutral fragments leads to protonated methanol. However, the latter, direct dissociation channel is energetically forbidden at low energies. Instead, an isomerization transition state is followed by proton transfer from a methyl group, which leads to the CH 3 (H)OH + ⋯CH 2 OH ion, the precursor to the CH 2 OH-, H 2 O-, and CH 3 -loss fragments after further isomerization steps, in part by a roaming mechanism. Water loss yields the ethanol cation, and two paths are proposed to account for m/z 49 fragment ions after CH 3 loss. The roaming pathways are quickly outcompeted by hydrogen bond breaking to yield CH 3 OH 2 + , which explains the dominance of the protonated methanol fragment ion in the mass spectrum. 

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