Creation of Gas-Phase Organo-Uranium Species by Removal of "yl" Oxo Ligands From UO Carboxylate Precursor Ions.

Rationale: 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 UO-phenide complexes [UO(CHFX)], X = Cl, Br, or I.

Methods: Samples of UO(OC-CHFX) were prepared by digesting UO with appropriate halogen-substituted carboxylic acids in deionized water. Solutions for ESI were created by diluting the digested sample in 50:50 HO/CHOH.

Synthesis of organo-uranium(II) species in the gas-phase using reactions between [UH] and nitriles.

One challenge in the quest to map the intrinsic reactivity of model actinide species has been the controlled synthesis of organo-actinide ions in the gas phase. We report here evidence that a series of gas-phase, σ-bonded [U-R] species (where R = CH, CH, CH, CH, or CH) can be generated for subsequent study of ion-molecule chemistry by using preparative tandem mass spectrometry (PTMS) ion-molecule reactions between [UH] and a series of nitriles. Density functional theory calculations support the hypothesis that the [U-R] ions are created in a pathway that involves intramolecular hydride attack and the elimination of neutral HCN.

Reactions of gas-phase uranyl formate/acetate anions: reduction of carboxylate ligands to aldehydes by intra-complex hydride attack.

In a previous study, electrospray ionization, collision-induced dissociation (CID), and gas-phase ion-molecule reactions were used to create and characterize ions derived from homogeneous precursors composed of a uranyl cation (UO) coordinated by either formate or acetate ligands [E. Perez, C. Hanley, S.

Gas-phase synthesis of [OU-X] (X = Cl, Br and I) from a UO precursor using ion-molecule reactions and an [OUCH] intermediate.

Difficulty in the preparation of gas-phase ions that include U in middle oxidation states(III,IV) have hampered efforts to investigate intrinsic structure, bonding and reactivity of model species. Our group has used preparative tandem mass spectrometry (PTMS) to synthesize a gas-phase U-methylidyne species, [OUCH], by elimination of CO from [UO(CCH)] [M. J.

Characterization of the Oxazolone and Macrocyclic Motifs in the b ( = 2-5) Product Ions from Collision-Induced Dissociation of Protonated Oligoglycine Peptides with Isomer-Selective, Cryogenic Vibrational Spectroscopy.

Collision-induced dissociation (CID) of small, protonated peptides leads to the formation of b-type fragment ions that can occur with several structural motifs driven by different covalent intramolecular bonding arrangements. Here, we characterize the so-called "oxazolone" and "macrocycle" ion structures that occur upon CID of oligoglycine peptides (G) ions ( = 2-6). This is determined by acquiring the vibrational band patterns of the cryogenically cooled, D-tagged ions obtained using isomer-selective, two-color IR-IR photobleaching and analyzing them with predicted (DFT) harmonic spectra for the candidate structures.

Conversion of a UO Precursor to UH and U Using Tandem Mass Spectrometry to Remove Both "yl" Oxo Ligands.

Multiple-stage collision-induced dissociation (CID) of a uranyl propiolate cation, [UO(OC-C≡CH)], can be used to prepare the U-methylidyne species [O═U≡CH] [ , , 796-805]. Here, we report that CID of [O═U≡CH] causes elimination of CO to create [UH], followed by a loss of H to generate U. A feasible, multiple-step pathway for the generation of [UH] was identified using DFT calculations.

Unusual Actinyl Complexes with a Redox-Active N,S-Donor Ligand.

Understanding the fundamental chemistry of soft N,S-donor ligands with actinides across the series is critical for separation science toward sustainable nuclear energy. This task is particularly challenging when the ligands are redox active. We herein report a series of actinyl complexes with a N,S-donor redox-active ligand that stabilizes different oxidation states across the actinide series.

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

Rationale: 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 (CS ).

Methods: 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 CS was admitted into the trap through a modified He inlet and precision leak valves.

Characterization of Uranyl Coordinated by Equatorial Oxygen: Oxo in UO versus Oxyl in UO.

Uranium trioxide, UO, has a T-shaped structure with bent uranyl, UO, coordinated by an equatorial oxo, O. The structure of cation UO is similar but with an equatorial oxyl, O. Neutral and cationic uranium trioxide coordinated by nitrates were characterized by collision induced dissociation (CID), infrared multiple-photon dissociation (IRMPD) spectroscopy, and density functional theory.

Destruction and reconstruction of UO using gas-phase reactions.

While the strong axial U[double bond, length as m-dash]O bonds confer high stability and inertness to UO22+, it has been shown that the axial oxo ligands can be eliminated or replaced in the gas-phase using collision-induced dissociation (CID) reactions. We report here tandem mass spectrometry experiments initiated with a gas-phase complex that includes UO22+ coordinated by a 2,6-difluorobenzoate ligand. After decarboxylation to form a difluorophenide coordinated uranyl ion, [UO2(C6F2H3)]+, CID causes elimination of CO, and then CO and C2H2 in sequential dissociation steps, to leave a reactive uranium fluoride ion, [UF2(C2H)]+.

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

We recently reported a detailed investigation of the collision-induced dissociation (CID) of [UO (NO ) ] and [UO (NO ) (O )] in a linear ion trap mass spectrometer (J. Mass Spectrom. DOI:10.

Intrinsic chemistry of [OUCH]: reactions with HO, CHC[triple bond, length as m-dash]N and O.

We report the first experimental study of the intrinsic chemistry of a U-methylidyne species, focusing on reaction of [OUCH]+ with H2O, O2 and CH3C[triple bond, length as m-dash]N in the gas phase. DFT was also used to determine reaction pathways, and establish the mechanism by which [OUCH]+ is formed through collision-induced dissociation of [UO2(C[triple bond, length as m-dash]CH)]+.

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

Electrospray ionization (ESI) can produce a wide range of gas-phase uranyl (UO ) complexes for tandem mass spectrometry studies of intrinsic structure and reactivity. We describe here the formation and collision-induced dissociation (CID) of [UO (NO ) ] and [UO (NO ) (O )] . Multiple-stage CID experiments reveal that the complexes dissociate in reactions that involve elimination of O , NO , or NO , and subsequent reactions of interesting uranyl-oxo product ions with (neutral) H O and/or O were investigated.

Formation and hydrolysis of gas-phase [UO (R)] : R═CH , CH CH , CH═CH , and C H.

The goals of the present study were (a) to create positively charged organo-uranyl complexes with general formula [UO (R)] (eg, R═CH and CH CH ) by decarboxylation of [UO (O C─R)] precursors and (b) to identify the pathways by which the complexes, if formed, dissociate by collisional activation or otherwise react when exposed to gas-phase H O. Collision-induced dissociation (CID) of both [UO (O C─CH )] and [UO (O C─CH CH )] causes H transfer and elimination of a ketene to leave [UO (OH)] . However, CID of the alkoxides [UO (OCH CH )] and [UO (OCH CH CH )] produced [UO (CH )] and [UO (CH CH )] , respectively.

Gas-Phase Deconstruction of UO: Mass Spectrometry Evidence for Generation of [OUCH] by Collision-Induced Dissociation of [UO(C≡CH)].

Because of the high stability and inertness of the U=O bonds, activation and/or functionalization of UO and UO remain challenging tasks. We show here that collision-induced dissociation (CID) of the uranyl-propiolate cation, [UO(OC-C≡CH)], can be used to prepare [UO(C≡CH)] in the gas phase by decarboxylation. Remarkably, CID of [UO(C≡CH)] caused elimination of CO to create [OUCH], thus providing a new example of a well-defined substitution of an "yl" oxo ligand of UO in a unimolecular reaction.

Isotope labeling and infrared multiple-photon photodissociation investigation of product ions generated by dissociation of [ZnNO(CHOH)]: Conversion of methanol to formaldehyde.

Electrospray ionization was used to generate species such as [ZnNO(CHOH)] from Zn(NO)•XHO dissolved in a mixture of CHOH and HO. Collision-induced dissociation of [ZnNO(CHOH)] causes elimination of CHOH to form [ZnNO(CHOH)]. Subsequent collision-induced dissociation of [ZnNO(CHOH)] causes elimination of 47 mass units (u), consistent with ejection of HNO.

Comparison of In Vitro Stereoselective Metabolism of Bupropion in Human, Monkey, Rat, and Mouse Liver Microsomes.

Background And Objectives: Bupropion is an atypical antidepressant and smoking cessation aid associated with wide intersubject variability. This study compared the formation kinetics of three phase I metabolites (hydroxybupropion, threohydrobupropion, and erythrohydrobupropion) in human, marmoset, rat, and mouse liver microsomes. The objective was to establish suitability and limitations  for subsequent use of nonclinical species to model bupropion central nervous system (CNS) disposition in humans.

Influence of Background HO on the Collision-Induced Dissociation Products Generated from [UONO].

Developing a comprehensive understanding of the reactivity of uranium-containing species remains an important goal in areas ranging from the development of nuclear fuel processing methods to studies of the migration and fate of the element in the environment. Electrospray ionization (ESI) is an effective way to generate gas-phase complexes containing uranium for subsequent studies of intrinsic structure and reactivity. Recent experiments by our group have demonstrated that the relatively low levels of residual HO in a 2-D, linear ion trap (LIT) make it possible to examine fragmentation pathways and reactions not observed in earlier studies conducted with 3-D ion traps (Van Stipdonk et al.

Collision-induced dissociation of [U O (ClO )] revisited: Production of [U O (Cl)] and subsequent hydrolysis to create [U O (OH)].

Rationale: In a previous study [Rapid Commun Mass Spectrom. 2004;18:3028-3034], collision-induced dissociation (CID) of [U O (ClO )] appeared to be influenced by the high levels of background H O in a quadrupole ion trap. The CID of the same species was re-examined here with the goal of determining whether additional, previously obscured dissociation pathways would be revealed under conditions in which the level of background H O was lower.

Uranyl/12-crown-4 Ether Complexes and Derivatives: Structural Characterization and Isomeric Differentiation.

The following gas-phase uranyl/12-crown-4 (12C4) complexes were synthesized by electrospray ionization: [UO(12C4)] and [UO(12C4)(OH)]. Collision-induced dissociation (CID) of the dication resulted in [UO(12C4-H)] (12C4-H is a 12C4 that has lost one H), which spontaneously adds water to yield [UO(12C4-H)(HO)]. The latter has the same composition as complex [UO(12C4)(OH)] produced by CID of [UO(12C4)(OH)] but exhibits different reactivity with water.

Cleaving Off Uranyl Oxygens through Chelation: A Mechanistic Study in the Gas Phase.

Recent efforts to activate the strong uranium-oxygen bonds in the dioxo uranyl cation have been limited to single oxo-group activation through either uranyl reduction and functionalization in solution, or by collision induced dissociation (CID) in the gas-phase, using mass spectrometry (MS). Here, we report and investigate the surprising double activation of uranyl by an organic ligand, 3,4,3-LI(CAM), leading to the formation of a formal U chelate in the gas-phase. The cleavage of both uranyl oxo bonds was experimentally evidenced by CID, using deuterium and O isotopic substitutions, and by infrared multiple photon dissociation (IRMPD) spectroscopy.

Thermodynamics and Reaction Mechanisms of Decomposition of the Simplest Protonated Tripeptide, Triglycine: A Guided Ion Beam and Computational Study.

We present a thorough characterization of fragmentations observed in threshold collision-induced dissociation (TCID) experiments of protonated triglycine (HGGG) with Xe using a guided ion beam tandem mass spectrometer (GIBMS). Kinetic energy-dependent cross-sections for 10 ionic products are observed and analyzed to provide 0 K barriers for six primary products: [b], [y + 2H], [b], CO loss, [y + 2H], and [a]; three secondary products: [a], [a], and [y + 2H - CO]; and two tertiary products: high energy [y + 2H] and [a - CO] after accounting for multiple ion-molecule collisions, internal energy of reactant ions, unimolecular decay rates, competition between channels, and sequential dissociations. Relaxed potential energy surface scans performed at the B3LYP-D3/6-311+G(d,p) level of theory are used to identify transition states (TSs) and intermediates of the six primary and one secondary products.

Gas Phase Reactions of Ions Derived from Anionic Uranyl Formate and Uranyl Acetate Complexes.

The speciation and reactivity of uranium are topics of sustained interest because of their importance to the development of nuclear fuel processing methods, and a more complete understanding of the factors that govern the mobility and fate of the element in the environment. Tandem mass spectrometry can be used to examine the intrinsic reactivity (i.e.