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1. 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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2. 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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3. Structural characterization of fatty acid anions via gas‐phase charge inversion using Mg(tri‐butyl‐terpyridine) 2 2+ reagent ions

   https://doi.org/10.1002/rcm.9741  

   Nsiah, Sarah T. ; Fabijanczuk, Kimberly C. ; McLuckey, Scott A. ( April 2024 , Rapid Communications in Mass Spectrometry)

   Free fatty acids and lipid classes containing fatty acid esters are major components of lipidome. In the absence of a chemical derivatization step, FA anions do not yield all of the structural information that may be of interest under commonly used collision‐induced dissociation (CID) conditions. A line of work that avoids condensed‐phase derivatization takes advantage of gas‐phase ion/ion chemistry to charge invert FA anions to an ion type that provides the structural information of interest using conventional CID. This work was motivated by the potential for significant improvement in overall efficiency for obtaining FA chain structural information.

   A hybrid triple quadrupole/linear ion‐trap tandem mass spectrometer that has been modified to enable the execution of ion/ion reaction experiments was used to evaluate the use of 4,4′,4″‐tri‐tert‐butyl‐2,2′:6′,2″‐terpyridine (ttb‐Terpy) as the ligand in divalent magnesium complexes for charge inversion of FA anions.

   Mg(ttb‐Terpy)₂²⁺complexes provide significantly improved efficiency in producing structurally informative products from FA ions relative to Mg(Terpy)₂²⁺complexes, as demonstrated for straight‐chain FAs, branched‐chain FAs, unsaturated FAs, and cyclopropane‐containing FAs. It was discovered that most of the structurally informative fragmentation from [FA‐H + Mg(ttb‐Terpy)]⁺results from the loss of a methyl radical from the ligand followed by radical‐directed dissociation (RDD), which stands in contrast to the charge‐remote fragmentation (CRF) believed to be operative with the [FA‐H + Mg(Terpy)]⁺ions.

   This work demonstrates that a large fraction of product ions from the CID of ions of the form [FA‐H + Mg(ttb‐Terpy)]⁺are derived from RDD of the FA backbone, with a very minor fraction arising from structurally uninformative dissociation channels. This ligand provides an alternative to previously used ligands for the structural characterization of FAs via CRF.

    

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4. Solvothermal Synthesis of [Cr 7 S 8 (en) 8 Cl 2 ]Cl 3  ⋅ 2H 2 O with Magnetically Frustrated [Cr 7 S 8 ] 5+ Double‐Cubes**

   https://doi.org/10.1002/chem.202103761  

   Gamage, Eranga H. ; Clark, Judith K. ; Yazback, Maher ; Cheng, Hai‐Ping ; Shatruk, Michael ; Kovnir, Kirill ( December 2021 , Chemistry – A European Journal)

   A novel transition metal chalcohalide [Cr₇S₈(en)₈Cl₂]Cl₃ ⋅ 2H₂O, with [Cr₇S₈]⁵⁺dicubane cationic clusters, has been synthesized by a low temperature solvothermal method, using dimethyl sulfoxide (DMSO) and ethylenediamine (en) solvents. Ethylenediamine ligand exhibits bi‐ and monodentate coordination modes; in the latter case ethylenediamine coordinates to Cr atoms of adjacent clusters, giving rise to a 2D polymeric structure. Although magnetic susceptibility shows no magnetic ordering down to 1.8 K, a highly negative Weiss constant,θ=−224(2) K, obtained from Curie‐Weiss fit of inverse susceptibility, suggests strong antiferromagnetic (AFM) interactions betweenS=3/2 Cr(III) centers. Due to the complexity of the system with (2S+1)⁷=16384 microstates from seven Cr³⁺centers, a simplified model with only two exchange constants was used for simulations. Density‐functional theory (DFT) calculations yielded the two exchange constants to beJ₁=−21.4 cm⁻¹andJ₂=−30.2 cm⁻¹, confirming competing AFM coupling between the shared Cr³⁺center and the peripheral Cr³⁺ions of the dicubane cluster. The best simulation of the experimental data was obtained withJ₁=−20.0 cm⁻¹andJ₂=−21.0 cm⁻¹, in agreement with the slightly stronger AFM exchange within the triangles of the peripheral Cr³⁺ions as compared to the AFM exchange between the central and peripheral Cr³⁺ions. This compound is proposed as a synthon towards magnetically frustrated systems assembled by linking dicubane transition metal‐chalcogenide clusters into polymeric networks.

    

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5. Mass spectrometry and computational study of collision-induced dissociation of 9-methylguanine–1-methylcytosine base-pair radical cation: intra-base-pair proton transfer and hydrogen transfer, non-statistical dissociation, and reaction with a water ligand

   https://doi.org/10.1039/d0cp01788d  

   Sun, Yan ; Moe, May Myat ; Liu, Jianbo ( July 2020 , Physical Chemistry Chemical Physics)

   null (Ed.)

   A combined experimental and theoretical study is presented on the collision-induced dissociation (CID) of 9-methylguanine–1-methylcytosine base-pair radical cation (abbreviated as [9MG·1MC]˙ + ) and its monohydrate ([9MG·1MC]˙ + ·H 2 O) with Xe and Ar gases. Product ion mass spectra were measured as a function of collision energy using guided-ion beam tandem mass spectrometry, from which cross sections and threshold energies for various dissociation pathways were determined. Electronic structure calculations were performed at the DFT, RI-MP2 and DLPNO-CCSD(T) levels of theory to identify product structures and map out reaction potential energy surfaces. [9MG·1MC]˙ + has two structures: a conventional structure 9MG˙ + ·1MC (population 87%) consisting of hydrogen-bonded 9-methylguanine radical cation and neutral 1-methylcytosine, and a proton-transferred structure [9MG − H]˙·[1MC + H] + (less stable, population 13%) formed by intra-base-pair proton transfer from the N1 of 9MG˙ + to the N3 of 1MC within 9MG˙ + ·1MC. The two structures have similar dissociation energies but can be distinguished in that 9MG˙ + ·1MC dissociates into 9MG˙ + and 1MC whereas [9MG – H]˙·[1MC + H] + dissociates into neutral [9MG – H]˙ radical and protonated [1MC + H] + . An intriguing finding is that, in both Xe- and Ar-induced CID of [9MG·1MC]˙ + , product ions were overwhelmingly dominated by [1MC + H] + , which is contrary to product distributions predicted using a statistical reaction model. Monohydration of [9MG·1MC]˙ + reversed the populations of the conventional structure (43%) vs. the proton-transferred structure (57%) and induced new reactions upon collisional activation, of which intra-base-pair hydrogen transfer produced [9MG + H] + and the reaction of the water ligand with a methyl group in [9MG·1MC]˙ + led to methanol elimination from [9MG·1MC]˙ + ·H 2 O. 

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