Mechanism and Energetics of the Hydrolysis of Th⁺To Form Th(OD)₃⁺: Guided Ion Beam and Theoretical Studies of ThO⁺, ThO₂⁺, and OThOD⁺Reacting with D₂O

Abstract

The kinetic energy dependences of the reactions of ThO+, ThO2 +, and OThOD+ with D2O, ThO2 + with D2, and OThOD+ with Xe were studied using guided ion beam tandem mass spectrometry. Exothermic formation of OThOD+ is the dominant process observed in reactions of both ThO+ and ThO2 + with D2O. Minor products formed in endothermic reactions include ThO2 +, DThO+, and ThO2D2 +. OThOD+ is also formed in the reaction of ThO2 + with D2 but in an endothermic process. Collision-induced dissociation (CID) of OThOD+ with Xe leads to endothermic loss of the hydroxide ligand. OThOD+ reacts further with D2O to form the associative complex ThO3D3 +, which is long-lived before dissociating back to the reactants. The OThOD+–D2O bond energy of the associative complex is measured to be 2.96 ± 0.05 eV by modeling the kinetic energy-dependent cross section for association using a phase space theory model that rigorously conserves angular momentum. By comparison with theory, this bond energy identifies the ThO3D3 + species as the trihydroxide cation, Th­(OD)3 +. From the endothermic reactions and CID of OThOD+ with Xe, the OTh+–D, OTh+–O, and OTh+–OD bond dissociation energies (BDEs) are measured to be 2.33 ± 0.24, 4.66 ± 0.15, and 6.00 ± 0.17 eV, respectively. All four of these BDEs are experimentally determined for the first time and agree reasonably well with values calculated at the B3LYP, B3PW91, and PBE0 levels of theory with cc-pVQZ basis sets. Complete potential energy surfaces for all reactions were calculated at the B3LYP/cc-pVTZ level and elucidate the mechanisms for all processes observed.

Threshold Collision-Induced Dissociation of Hydrated Thorium(IV) Trihydroxide Cation: Experimental and Theoretical Investigation of the Binding Energies for Th(OH)3+(H2O)nComplexes (n= 1–4)

“…Analysis of the ThO 3 D 3 + association cross section yields the bond dissociation energy (BDE) of the association complex. Comparison of this BDE to theoretical values unambiguously determined that the ThO 3 D 3 + species is the thorium trihydroxide cation, Th(OD) 3 + , and not the other possible isomer, OThOD + (D 2 O) …”

“…Gas-phase studies where solvent effects are absent can provide such benchmarks that are most directly and easily compared to theoretical results. In this context, our group is dedicated to establishing accurate experimental thermodynamic data for gas-phase actinide compounds. − …”

“…The binding energies decrease as more waters are added, and as a result, the efficiency of the fourth hydration was insufficient to be observed under their experimental conditions, i.e., for their longest reaction time of 10 s in a quadrupole ion trap (QIT) . Recently, we have experimentally elucidated the detailed mechanism and energetics of the hydrolysis of Th + to form thorium trihydroxide cation using a guided ion beam tandem mass spectrometer (GIBMS). , Using deuterated water, we showed that Th + reacts with water to efficiently form both ThO + and ThOD + . In subsequent reactions, OThOD + is the dominant product formed in the reactions of both ThO + and ThO 2 + with water, and OThOD + further reacts with water to form the association product, ThO 3 D 3 + , in an efficient exothermic and barrierless reaction.…”

Methane Adducts of Gold Dimer Cations: Thermochemistry and Structure from Collision-Induced Dissociation and Association Kinetics

“…For instance, Klippenstein et al extracted BDEs from the rate of radiatively stabilized compounds in ion cyclotron resonance (ICR) MS experiments . Armentrout and co-workers derived BDEs from long-lived association complexes in guided ion beam tandem MS (GIBMS) experiments by modeling the behavior as a function of collision energy and extrapolating to collisionless conditions. − Similar to the systems here, Lang et al derived bond strengths for methane adducts to Au + 2–6 clusters, seeing a general weakening of the bond as cluster size increased . A similar statistical modeling approach to that used here has been applied to systems with experimentally defined BDEs in order to determine the average intermolecular energy transfer per collision, ⟨Δ E ⟩. − The intimate link between the BDE and clustering kinetics is clear; however, a primary question addressed here is to what accuracy the BDE may be determined.…”

Photoelectron Spectroscopic and ab Initio Computational Studies of the Anion, HThO–

“…Due to its [Rn]­6d 2 7s 2 electronic configuration, thorium is normally present in its tetravalent state. In aqueous solutions, for example, thorium forms numerous hydroxides, such as, Th­(OH) 3 + , Th­(OH) 2 2+ , Th­(OH) 3+ , and Th 2 (OH) 2 6+ . − However, in matrix isolation studies, where laser-ablated thorium atoms and water molecules were co-deposited on an argon ice, HTh­(OH) and HThO were found to be the major intermediates and reaction products, with only residual amounts of H 2 ThO, HThO­(OH), HTh­(OH) 3 , and OTh­(OH) 2 detected. Interestingly, there was no evidence of thorium hydroxide, ThOH, having been formed.…”