Production and collision‐induced dissociation of gas‐phase, water‐ and alcohol‐coordinated uranyl complexes containing halide or perchlorate anions

Abstract

Electrospray ionization was used to generate mono‐positive gas‐phase complexes of the general formula [UO2A(S)n]+ where A = OH, Cl, Br, I or ClO4, S = H2O, CH3OH or CH3CH2OH, and n = 1–3. The multiple‐stage dissociation pathways of the complexes were then studied using ion‐trap mass spectrometry. For H2O‐coordinated cations, the dissociation reactions observed included the elimination of H2O ligands and the loss of HA (where A = Cl, Br or I). Only for the Br and ClO4 versions did collision‐induced dissociation (CID) of the hydrated species generate the bare, uranyl–anion complexes. CID of the chloride and iodide versions led instead to the production of uranyl hydroxide and hydrated UO. Replacement of H2O ligands by alcohol increased the tendency to eliminate HA, consistent with the higher intrinsic acidity of the alcohols compared to water and potentially stronger UO2O interactions within the alkoxide complexes compared to the hydroxide version. Copyright © 2004 John Wiley & Sons, Ltd.

Vibrational spectra of discrete UO22+ halide complexes in the gas phase

“…Using electrospray uranyl halide coordination complexes can be generated [12] and then trapped in a Fourier transform ion cyclotron resonance mass spectrometer, where they can be isolated and then photodissociated using light from a free electron laser (FEL) in the mid-IR [13][14][15], or from an optical parametric oscillator laser tuned to higher frequencies corresponding to H-stretching regions [16][17][18][19][20][21][22][23][24]. In the mid-IR region of the spectrum, photons are not sufficiently energetic to cause dissociation needed to observe vibrational fundamentals.…”

Collision‐induced dissociation of [UVIO2(ClO4)]+ revisited: Production of [UVIO2(Cl)]+ and subsequent hydrolysis to create [UVIO2(OH)]+

“…In the prior study, MS n CID of [U VI O 2 (ClO 4 )(H 2 O) 3 ] + caused the serial elimination of H 2 O ligands to generate [U VI O 2 (ClO 4 )] + . The primary dissociation products observed from CID of [U VI O 2 (ClO 4 )] + were [U VI O 2 (OH)] + and [U V O 2 ] + at m/z 287 and 270, respectively.…”

“…As noted earlier, our previous study involved the use of MS n experiments with a 3D ion trap instrument to determine the dissociation pathways for [U VI O 2 (ClO 4 )] + coordinated by water or alcohol ligands . At each CID stage, the product ion spectra contained a mix of product ions formed from fragmentation reactions and H 2 O adducts to those ions.…”

“…Electrospray ionization (ESI) effectively produces gas‐phase ions with uranium in high oxidation states, and our group was among the first to use ESI to create gas‐phase, doubly charged complexes with ligands such as acetonitrile (acn) or acetone (aco), for studies of intrinsic structure and reactivity (i.e. outside the influence of solvent or other condensed phase effects) in a species‐specific fashion . Since then, ESI has been used to create gas‐phase uranyl species for a range of tandem mass spectrometry (MS/MS), anion photoelectron spectroscopy, and ion mobility studies .…”

“…In one earlier study by our group that used a 3D quadrupole ion trap instrument, MS n CID was used to map the dissociation pathways for several cationic species composed of (1) the uranyl ion, (2) a halide or perchlorate anion, and (3) water or alcohol . For complexes with coordinating water molecules, MS n CID led to the formation of [U VI O 2 (ClO 4 )] + and the dominant product ions generated by collisional activation of this ion were [U VI O 2 (OH)] + and [U V O 2 ] + .…”