Formation of bare UO2(2+) and NUO(+) by fragmentation of gas-phase uranyl-acetonitrile complexes.

In a prior study [Van Stipdonk; et al. J. Phys.

Dissociation of gas-phase bimetallic clusters as a probe of charge densities: the effective charge of uranyl.

Complementary experimental and computational methods for evaluating relative charge densities of metal cations in gas-phase clusters are presented. Collision-induced dissociation (CID) and/or density functional theory computations were performed on anion clusters of composition MM'A(m+n+1)(-), where the two metal ions have formal charge states M(m+) and M'(n+) and A is an anion, NO3(-), Cl(-), or F(-) in this work. Results for alkaline earth and lanthanide metal ions reveal that cluster CID generally preferentially produces MA(m+1)(-) and neutral M'An if the surface charge density of M is greater than that of M': the metal ion with the higher charge density takes the extra anion.

Activation of gas-phase uranyl: from an oxo to a nitrido complex.

The uranyl moiety, UO2(2+), is ubiquitous in the chemistry of uranium, the most prevalent actinide. Replacing the strong uranium-oxygen bonds in uranyl with other ligands is very challenging, having met with only limited success. We report here uranyl oxo bond activation in the gas phase to form a terminal nitrido complex, a previously elusive transformation.

Synthesis and properties of uranium sulfide cations. An evaluation of the stability of thiouranyl, {S═U═S}2+.

Atomic uranium cations, U(+) and U(2+), reacted with the facile sulfur-atom donor OCS to produce several monopositive and dipositive uranium sulfide species containing up to four sulfur atoms. Sequential abstraction of two sulfur atoms by U(2+) resulted in US2(2+); density functional theory computations indicate that the ground-state structure for this species is side-on η(2)-S2 triangular US2(2+), with the linear thiouranyl isomer, {S═U(VI)═S}(2+), some 171 kJ mol(-1) higher in energy. The result that the linear thiouranyl structure is a local minimum at a moderate energy suggests that it should be feasible to stabilize this moiety in molecular compounds.

Proton transfer in Th(IV) hydrate clusters: a link to hydrolysis of Th(OH)(2)(2+) to Th(OH)(3)(+) in aqueous solution.

Gas-phase reactions of thorium hydroxide cations with water were studied in an ion trap and by density functional theory. The Th(OH)(2)(2+) ion adds five inner-shell water molecules. Addition of outer-shell water molecules to produce the Th(OH)(2)(2+)·(H(2)O)(6-8) yields Th(OH)(3)(+)·(H(2)O)(0-3) by intracluster proton transfer and elimination of a protonated water cluster, (H(3)O)(+)(H(2)O)(2).

Gas-phase reaction studies of dipositive hafnium and hafnium oxide ions: generation of the peroxide HfO2(2+).

Fourier transform ion cyclotron resonance mass spectrometry was used to characterize the gas-phase reactivity of Hf dipositive ions, Hf(2+)and HfO(2+), toward several oxidants: thermodynamically facile O-atom donor N(2)O, ineffective donor CO, and intermediate donors O(2), CO(2), NO, and CH(2)O. The Hf(2+) ion exhibited electron transfer with N(2)O, O(2), NO, and CH(2)O, reflecting the high ionization energy of Hf(+). The HfO(2+) ion was produced by O-atom transfer to Hf(2+) from N(2)O, O(2), and CO(2), and the HfO(2)(2+) ion by O-atom transfer to HfO(2+) from N(2)O; these reactions were fairly efficient.

On the origins of faster oxo exchange for uranyl(V) versus plutonyl(V).

Activation of uranyl(V) oxo bonds in the gas phase is demonstrated by reaction of U(16)O(2)(+) with H(2)(18)O to produce U(16)O(18)O(+) and U(18)O(2)(+). In contrast, neptunyl(V) and plutonyl(V) are comparatively inert toward exchange. Computed potential energy profiles (PEPs) reveal a lower yl oxo exchange transition state for uranyl(V)/water as compared with neptunyl(V)/water and plutonyl(V)/water.

Gas-phase oxidation reactions of Ta2+: synthesis and properties of TaO(2+) and TaO2(2+).

Gas-phase reactions of Ta(2+) and TaO(2+) with oxidants, including thermodynamically facile O-atom donor N(2)O and ineffective donor CO, as well as intermediate donors C(2)H(4)O (ethylene oxide), H(2)O, O(2), CO(2), NO, and CH(2)O, were studied by Fourier transform ion cyclotron resonance mass spectrometry. All oxidants reacted with Ta(2+) by electron transfer yielding Ta(+), in accord with the high second ionization energy of Ta (ca. 16 eV).

Reduction of mercury(II) by the carbon dioxide radical anion: a theoretical and experimental investigation.

The laser flash photolysis technique (λ(exc) = 266 nm) was used to investigate the mechanism of the HgCl(2) reduction mediated by CO(2)(·-) radicals in the temperature range 291.7-308.0 K.

Gas-phase reactions of uranate ions, UO(2)(-), UO(3)(-), UO(4)(-), and UO(4)H(-), with methanol: a convergence of experiment and theory.

Bimolecular reactions of uranium oxide molecular anions with methanol have been studied experimentally, by Fourier transform ion cyclotron resonance mass spectrometry, and computationally, by density functional theory (DFT). The primary goals were to provide fundamental insights into mechanistic and structural details of model reactions of uranium oxides with organics, and to examine the validity of theoretical modeling of these types of reactions. The ions UO(3)(-), UO(4)(-), and UO(4)H(-) each reacted with methanol to give a singular product; the primary products each exhibited sequential reactions with two additional methanol molecules to again give singular products.

A combined theoretical and experimental study on the oxidation of fulvic acid by the sulfate radical anion.

The kinetics of the reaction of sulfate radicals with the IHSS Waskish peat fulvic acid in water was investigated in the temperature range from 289.2 to 305.2 K.

Topological analysis of the reaction of uranium ions (U+, U2+) with N2O in the gas phase.

Density functional theory calculations were performed to study the ability of uranium cations, U(+) and U(2+), to activate the N-N and N-O bonds of N(2)O. A close description of the reaction pathways leading to different reaction products is presented. The obtained results are compared with previous experimental works.

Topological insights into the nature of the halogen-carbon bonds in dimethylhalonium ylides and their cations.

In this study the nature of the bonding in a series of dimethylhalonium ylides (fluoronium, chloronium, bromonium and iodonium) was analyzed by means of topological methodologies (AIM and ELF analysis), to document the changes in the nature of the C-X bonds (X = F, Cl, Br, I) upon the series. For the sake of comparison the same study was performed on the corresponding dimethylhalonium cations (XC 2H 6 (+)) and the XCH 3 series. The wave functions used for the topological analysis were obtained at B3LYP level using extended triple-zeta basis sets.

Mechanistic aspects of the reaction of Th+ and Th2+ with water in the gas phase.

Density functional theory calculations were performed to study the gas-phase reaction of Th(+) and Th(2+) with water. An in-depth analysis of the reaction pathways leading to different reaction products is presented. The obtained results are compared to experimental data and to the previously studied reactions of U cations with water.

Theoretical and experimental investigation on the oxidation of gallic acid by sulfate radical anions.

By monitoring the decay of SO4*- after flash photolysis of aqueous solutions of S2O82- at different pH values, the kinetics of the reaction of SO4*- radicals with gallic acid and the gallate ion was investigated. The bimolecular rate constants for the reactions of the sulfate radicals with gallic acid and the gallate ion were found to be (6.3 +/- 0.

Gas-phase chemistry of actinides ions: new insights into the reaction of UO+ and UO2+ with water.

The ability of uranium monoxide cations, UO+ and UO2+, to activate the O-H bond of H2O was studied by using two different approaches of the density functional theory. First, relativistic small-core pseudopotentials were used together with B3LYP hybrid functional. In addition, frozen-core PW91-PW91 calculations were performed within the ZORA approximation.

Activation of methane by the iron dimer cation. A theoretical study.

A detailed investigation of the reaction mechanisms underlying the observed reactivity of the iron dimer cation with respect to methane has been performed by density functional hybrid (B3LYP) and nonhybrid (BPW91) calculations. Minima and transition states have been fully optimized and characterized along the potential energy surfaces leading to three different exit channels for both the ground and the first excited states of the dimer. A comparison with our previous work covering the reactivity of the Fe(+) monomer was made to underline similarities and differences of the reaction mechanisms.

Acetylene cyclotrimerization by early second-row transition metals in the gas phase. A theoretical study.

The acetylene cyclotrimerization reaction mediated by the left-hand-side bare transition metal atoms Y, Zr, Nb, and Mo has been studied theoretically, employing DFT in its B3LYP formulation. The complete reaction mechanism has been analyzed, identifying intermediates and transition states. Both the ground spin state and at least one low-lying excited state have been considered to establish whether possible spin crossings between surfaces of different multiplicity can occur.

Energetic and topological analyses of the oxidation reaction between Mo(n) (n = 1, 2) and N2O.

The interaction between molybdenum, atom, and dimer, with nitrous oxide has been investigated using density functional theory. The analysis of the potential energy surfaces for both reactions has revealed that a single molybdenum atom can activate the N--O bond of N2O requiring a small activation energy. However, the presence of several intersystem crossings between three different spin states, namely, septet, quintet and triplet states, seems to be the major constraint to the Mo + N2O reaction.

Density functional study of ammonia activation by late first-row transition metal cations.

Density functional theory (DFT) in its B3LYP implementation is used to investigate the reaction of ammonia with the late (Co(+), Ni(+), and Cu(+)) first-row transition metal cations in both high- and low-spin states. The potential energy surfaces (PES's) leading to three different exit channels are closely examined. The binding energies for the reaction products are calculated and compared with the corresponding experimental values.

Energetic and topological analysis of the reaction of Mo and Mo2 with NH3, C2H2, and C2H4 molecules.

The Density functional theory has been applied to characterize the structural features of Mo(1,2)-NH(3),-C(2)H(4), and -C(2)H(2) compounds. Coordination modes, geometrical structures, and binding energies have been calculated for several spin multiplets. It has been shown that in contrast to the conserved spin cases (Mo(1,2)-NH(3)), the interaction between Mo (or Mo(2)) and C(2)H(4) (or C(2)H(2)) are the low-spin (Mo-C(2)H(4) and -C(2)H(2)) and high-spin (Mo(2)-C(2)H(4) and -C(2)H(2)) complexes.

Reaction of bare VO+ and FeO+ with ammonia: a theoretical point of view.

The potential energy surfaces corresponding to the dehydration reaction of NH(3) by VO(+) ((3)Sigma, (1)Delta, (5)Sigma) and FeO(+) ((6)Sigma, (4)Delta) metal oxide cations have been investigated within the framework of the density functional theory in its B3LYP formulation and by employing new optimized basis sets for iron and vanadium. The reaction is proposed to occur through two hydrogen shifts from the nitrogen to the oxygen atom giving rise to multicentered transition states. Possible spin crossing between surfaces at different spin multiplicities has been considered.