Isotope effects on band intensities in the <Emphasis Type="Italic">B</Emphasis><Superscript>2</Superscript>Σ<Superscript>+</Superscript>-<Emphasis Type="Italic">X</Emphasis><Superscript>2</Superscript>Σ<Superscript>+</Superscript> system of GaO isotopomers

Relative intensities of eight vibronic bands, belonging to the Δυ = −2 sequence of the B ²Σ⁺ −X ²Σ⁺ electronic transition of four GaO isotopomers have been measured and interpreted in terms of possible isotope effects on the parameters governing the band intensity. Obtained results showed very small isotope effect on the Franck-Condon factors and r-centroids and revealed that the observed intensity ratios of the corresponding isotope bands are controlled mainly by the isotope abundance of ⁶⁹Ga and ⁷¹Ga in natural gallium. The article is published in the original.     

CN (<Emphasis Type="Italic">B</Emphasis><Superscript>2</Superscript>Σ<Superscript>+</Superscript> → <Emphasis Type="Italic">X</Emphasis><Superscript>2</Superscript>Σ<Superscript>+</Superscript>) Violet System in a Cold Atmospheric-Pressure Argon Plasma Jet

\( {\text{CN}} (B^{2}\Sigma ^{ + } \to X^{2}\Sigma ^{ + } ) \) violet system was investigated using optical emission spectroscopy in a non-equilibrium microwave atmospheric-pressure plasma jet in argon expanding in air. From the analysis of the emission spectra of the discharge in the range of 380 and 400 nm, the violet system of CN was found to be overlapped with the \( {\text{N}}_{2}^{ + } \left( {B^{2}\Sigma _{u}^{ + } , v = 1 \to X^{2}\Sigma _{g}^{ + } , v = 1} \right) \) and \( {\text{N}}_{2} \left( {C^{3}\Pi _{u} \to B^{3}\Pi _{g} } \right) \) bands, sequence \( \Delta \upsilon = - \;3 \). A numerical disentangle technique, developed in this work, permitted to obtain a well resolved violet system from the different systems observed, namely the nitrogen First Negative and the Second Positive systems. The \( {\text{CN}} (B^{2}\Sigma ^{ + } \to X^{2}\Sigma ^{ + } ) \) band head intensity was determined and analysed as function of discharge powers between 30 and 150 W and fluxes between 2.5 and 10.0 slm. With aid of this numerical approach it was also possible to obtain the rotational temperature, from (1600 ± 100) to (2300 ± 100) K and vibrational temperature between (9000 ± 800) and (14,000 ± 800) K along the plasma jet. The kinetics of \( {\text{CN}} (B^{2}\Sigma ^{ + } ) \) state was analysed as well.     

Theoretical evaluation of the radiative lifetimes of LiCs and NaCs in the A<Superscript>1</Superscript>Σ<Superscript>+</Superscript> state

Calculations of the adiabatic potential energy curves and the transition dipole moments between the ground (A¹Σ⁺) and the first excited (A¹Σ⁺) states have been determined for the LiCs and NaCs molecules. The calculations are performed using an ab initio approach based on non-empirical pseudopotentials for Cs⁺, Li⁺ and Na⁺ cores, parameterized l-dependent polarization potentials and full configuration interaction calculations. The potential energy curves and the transition dipole moment are used to estimate the radiative lifetimes of the vibrational levels of the A⁺Σ⁺ state using the Franck–Condon (FC) approximation and the approximate sum rule method. The radiative lifetimes associated with the A⁺Σ⁺ state are presented here for the first time. These data can help experimentalists to optimize photoassociative formation of ultracold molecules and their longevity in a trap or in an optical lattice.     

Test study on the excitation spectra of the N<Subscript>2</Subscript>–He van der Waals molecule

We have performed ab initio fourth-order Møller–Plesset perturbation theory calculations in the framework of the supermolecule approach on the vertical excitation spectra of the weakly bound van der Waals N₂–He dimer. They indicate a ``T-shaped' stablest ground N<sub>2</sub>(X<sup>1</sup><sub>g</sub><sup>+</sup>)–He(<sup>1</sup>S) electronic state with a well depth, D<sub>e</sub>, of 21.63 cm<sup>–1</sup> at a minimum distance, R<sub>e</sub>, of 3.44 Å and zero-point vibration correction, D<sub>o</sub>, of 7.07 cm<sup>–1</sup>. They also indicate a ``T-shaped' stablest excited conformer with R_e=3.25 Å, D_e=36.85 cm^–1 and D_o=17.06 cm^–1 for the N₂(B³_g)–He(¹S) triplet electronic level. In order to investigate the use of less-demanding correlation methods, test density functional theory calculations using the mPW1PW exchange–correlation functional are also presented for comparison.     

Theoretical study on the ion–molecule reaction of HCN<Superscript>+</Superscript> with NH<Subscript>3</Subscript>

A detailed theoretical study is carried out at the B3LYP/6-311G(d,p) and CCSD(T)/6-311++G(3df,2pd) (single-point) levels as an attempt to investigate the mechanism of the little understand ion–molecule reaction between HCN⁺ and NH₃. Various possible reaction pathways are considered. It is shown that six dissociation products P ₁ (NH₃ ⁺ + HCN), P ₂ (NH₄ ⁺ + CN), P ₃ (NH₃ ⁺ + HNC), P ₉ (HCNH⁺ + NH₂) P ₁₀ (NCNH₃ ⁺ + H), and P ₁₂ (HNCNH₂ ⁺ + H) are both thermodynamically and kinetically feasible. Among these products, P ₁ is the most competitive product with predominant abundance. P ₃ and P ₉ may be the second feasible products with comparable yields. P ₁₂ may be the least possible product followed by the almost negligible P ₂ and P ₁₀ . Because the isomers and transition states involved in the HCN⁺ + NH₃ reaction all lie below the reactant, the title reaction is expected to be rapid, which is consistent with the measured large rate constant in experiment. The title reaction may have a potential relevance in Titan’s atmosphere, where the temperature is very low. Furthermore, our calculated results are compared with the previous experimental findings.     

Photochemical arene exchange in the naphthalene complex [CpRu(η<Superscript>6</Superscript>-C <Subscript>10</Subscript>H<Subscript>8</Subscript>)]<Superscript>+</Superscript>

The cation [CpRu(η⁶-C₁₀H₈)]⁺ was shown to exchange naphthalene for other arenes under visible-light irradiation to form the complexes [CpRu (η⁶-arene)]⁺ (arene = C₆H₆, 1,4-C₆H₄Me₂, 1,3,5-C₆H₃Me₃, or 1,2,4,5-C ₆H₂Me₄) in 70–95% yields. The reaction rate of exchange decreases in the series arene = 1,4-C₆H₄Me₂ > C₆H₆ > 1,3,5-C₆H₃Me₃ > 1,2,4,5-C ₆H₂Me₄ >> C₆Me₆ and increases with the coordinating ability of the solvent in the order CH₂Cl₂ < THF—CH₂Cl₂ mixture (1: 1) < acetone.     

Synthesis of a <Superscript>188</Superscript>Re–DTPMP complex using carrier-free <Superscript>188</Superscript>Re and study of its stability

Labeling of diethylenetriamine-N,N,N′,N″,N″-pentakis(methylenephosphonic) acid (DTPMP) with rhenium-188 using stannous chloride as a reducing agent has been investigated. Dependence of the yield of the ¹⁸⁸Re–DTPMP complex on the concentration of the reducing agent, pH, reaction time, temperature, ascorbic acid and amount of carrier added has been studied. Under optimum conditions, the labeling yield of ¹⁸⁸Re–DTPMP complex is 95% for the carrier-free ¹⁸⁸Re but with the carrier-added ¹⁸⁸Re the labeling yield is more than 97%. Furthermore, the stability of the ¹⁸⁸Re–DTPMP complex against pH change and dilution with saline has been also studied. It is found that the addition of carrier stabilizes the ¹⁸⁸Re–DTPMP complex against pH change and dilution.     

Thermal arene exchange in the naphthalene complex [CpRu(η<Superscript>6</Superscript>-C<Subscript>10</Subscript>H<Subscript>8</Subscript>)]<Superscript>+</Superscript>

Naphthalene in the [CpRu(⁶−C₁₀H₈)]⁺ complex (1) is substituted for other arenes under reflux in 1,2-dichloroethane to form the [CpRu(⁶-arene)]⁺ cations (arene = C₆H₆, 1,2-C₆H₄Me₂, 1,2,4,5-C₆H₂Me₄, or C₆Me₆) in 70–80% yields. The reaction is accelerated in the presence of a catalytic amount of acetonitrile. The structure of [1]PF₆ was established by X-ray diffraction.     

A theoretical study on the dynamics of the gas phase reaction of NH<Subscript>2</Subscript>(<Superscript>2</Superscript>B<Subscript>1</Subscript>) with HO<Subscript>2</Subscript>(<Superscript>2</Superscript>A″)

Quasi-classical trajectory calculations and stochastic one-dimensional chemical master equation simulation methods are used to study the dynamics of the reaction of amidogen radical [NH₂(²B₁)] with hydroperoxyl radical [HO₂(²A″)] on the lowest singlet electronic state. The title complex reaction takes place on a multi-well multichannel potential energy surface consisting of three deep potential wells and one van der Waals complex. In quasi-classical trajectory calculations a new analytical potential energy surface based on CCSD(T)/aug-cc-pVTZ//MPW1K/6-31+G(d,p) ab initio method was driven and used to study the dynamics of the title reaction. In quasi-classical trajectory calculations, the reactive cross sections and reaction probabilities are determined for 200–2000 K relative translational energies to calculate the rate constants. The same ab initio method was used to have the necessary data for solving the one-dimensional chemical master equation to calculate the rate constants of different channels. In solving the master equation, the Lennard-Jones potential model was used to form the collision between the collider gases. The fractional populations of different intermediates and products in the early stages of the reaction were examined to determine the role of the energized intermediates and the van der Waals complex on the dynamics of the title reaction. Although the calculated total rate constants from both methods are in good agreement with the reported experimental values in the literature, the quasi-classical trajectory simulation predicts the formation of NH₂O + OH as the major channel in the title reaction in accordance with the previous studies (Sumathi and Peyerimhoff, Chem. Phys. Lett., 263:742–748, 1996), while the stochastic master equation simulation predicts the formation of HNO + H₂O as the major products.     

The Formation of OH*(<Superscript>2</Superscript>Σ<Superscript>+</Superscript>) Radical in the Reaction of Hydrogen with Oxygen behind a Shock Wave in Nonequilibrium Conditions

The mechanism of formation of the electronically excited radical OH*(A²Σ⁺) has been studied by analyzing calculations quantitatively describing the results of shock wave experiments carried out in order to determine the moment of maximum OH* radiation at temperatures T < 1500 K and pressures P ≤ 2 atm in the H₂ + O₂ mixtures diluted by argon when the vibrational nonequilibrium is a factor determining the mechanism and rate of the overall process. In kinetic calculations, the vibrational nonequilibrium of the initial H₂ and O₂ components, the HO₂, OH(X²Π), O₂*(¹Δ) intermediates, and the reaction product H₂O were taken into account. The analysis showed that under these conditions the main contribution to the overall process of OH* formation is caused by the reactions OH + Ar → OH* + Ar, H₂ + HO₂ → OH* + H₂O, H₂ + O*(¹D) → OH* + H, HO² + O → OH* + O² and H + H²O → OH* + H², which occur in the vibrational nonequilibrium mode (their activation barrier is overcome due to the vibrational excitation of reactants), and by H + O₃ → OH* + O₂ and H + H₂O₂ → OH* + H₂O, which are reverse to the reactions of chemical quenching.     

Stereo-dynamics study of O + HCl → OH + Cl reaction on the <Superscript>3</Superscript>A″, <Superscript>3</Superscript>A′, and <Superscript>1</Superscript>A′ states

Using three accurate potential energy surfaces of the ³A″, ³A′, and ¹A′ states constructed recently, we present a quasi-classical trajectory (QCT) calculation for O + HCl (v = 0, j = 0) → OH + Cl reaction at the collision energies (E _col) of 14.0–20.0 kcal/mol. The three angular distribution functions—P(q_r ) P(\theta_{r} ) , P(j_r ) P(\varphi_{r} ) , and P(q_r ,j_r ) P(\theta_{r} ,\varphi_{r} ) , together with the four commonly used polarization-dependent differential cross-sections, \frac2ps \fracds₀₀ dw_t , \frac2ps \fracds₂₀ dw_t , \frac2ps \fracds_{22 +} dw_t , \textand \frac2ps \fracds_{21 -} dw_t {\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{00} }}{{d\omega_{t} }}},\,{\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{20} }}{{d\omega_{t} }}},\,{\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{22 + } }}{{d\omega_{t} }}},\,{\text{and}}\,{\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{21 - } }}{{d\omega_{t} }}} are exhibited to get an insight into the alignment and the orientation of the product OH radical. There is a similar behavior of the tendency scattering direction for the two triplet electronic states (³A″ and ³A′)—backward scattering dominates, however, forward scattering prevails for the case of ¹A′ state. Also, obvious differences have been found in the stereo-dynamical information, which reveals the influences of the potential energy surface and the collision energy. The degrees of polarization and the influence of the collision energy on the stereo-dynamics characters of the title reaction are both demonstrated in the order of ³A′ > ³A″ > ¹A′.     

Optimization of the labeling yield by determination of the Cu<Superscript>+</Superscript>–acetonitrile complex constant in Cu<Superscript>+</Superscript>-catalyzed nucleophilic exchange reactions in mixed solvent conditions

To apply the Cu⁺-assisted nucleophilic exchange based radioiodination of aromatic compounds for more lipophilic compounds the reaction is carried out in mixed solvent conditions. Due to its physicochemical properties acetonitrile is an attractive solvent. Although acetonitrile forms complexes with Cu⁺ decreasing the labeling yield. This article describes a method for the determination of the complex constant at labeling temperature based on a Lineweaver–Burk approach, relating the reaction rate constant and the concentration of precursor in presence of different amounts of acetonitrile. The method also allows to calculate the adjusted amount of copper salt in order to obtain the same high labeling yield as obtained in absence of acetonitrile.     

Production of Gas-Phase Uranium Fluoroanions Via Solubilization of Uranium Oxides in the [1-Ethyl-3-Methylimidazolium]<Superscript>+</Superscript>[F(HF)<Subscript>2.3</Subscript>]<Superscript>−</Superscript> Ionic Liquid

A new methodology for gas-phase uranium ion formation is described in which UO₂ is dissolved in neat N-ethyl,N′-methylimidazolium fluorohydrogenate ionic liquid [EMIm⁺][F(HF)_2.3^?], yielding a blue-green solution. The solution was diluted with acetonitrile and then analyzed by electrospray ionization mass spectrometry. UF₆^? (a U(V) species) was observed at m/z?=?352, and other than cluster ions derived from the ionic liquid, nothing else was observed. When the sample was analyzed using infusion desorption chemical ionization, UF₆^? was the base peak, and it was accompanied by a less intense UF₅^? that most likely was formed by elimination of a fluorine radical from UF₆^?. Formation of UF₆^? required dissolution of UO₂ followed by or concurrent with oxidation of uranium from the +?4 to the +?5 state and finally formation of the fluorouranate. Dissolution of UO₃ produced a bright yellow solution indicative of a U(VI) species; however, electrospray ionization did not produce abundant U-containing ions. The abundant UF₆^? provides a vehicle for accurate measurement of uranium isotopic abundances free from interference from minor isotopes of other elements and a convenient ion synthesis route that is needed gas-phase structure and reactivity studies like infrared multiphoton dissociation and ion-molecule dissociation and condensation reactions. The reactive fluorohydrogenate ionic liquid may also enable conversion of uranium in oxidic matrices into uranium fluorides that slowly oxidize to uranyl fluoride under ambient conditions, liberating the metal for facile measurement of isotope ratios without extensive chemical separations.

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A simple and quick method for the preparation of radionuclide <Superscript>87</Superscript>Y/<Superscript>87m</Superscript>Sr generator using the <Superscript>nat</Superscript>Rb(α,xn)<Superscript>87</Superscript>Y reaction

A rapid method for the preparation of ⁸⁷Y/^87mSr radionuclide generator from a rubidium chloride target irradiated with 35 MeV α-particles is described. A simple two-step procedure is used to obtain a carrier-free ^87mSr isotope with a high enough radiochemical yield and high purity in the final aqueous fraction.     

A theoretical study of the interaction between [HB≡CH]<Superscript>−</Superscript>, [H<Subscript>2</Subscript>B=CH<Subscript>2</Subscript>]<Superscript>−</Superscript>, and boratabenzene anions with alkali and alkaline earth metals: properties and structures

The nature of [HB≡CH]⁻, [H₂B=CH₂]⁻, and boratabenzene interactions with alkaline and alkaline earth metals are studied by ab initio calculations. The interaction energies are calculated at the B3LYP/6-311++G(d,p) level. The calculations suggest that the cation size and charge are two influential factors that affect the nature of the interaction. AIM and NBO analyses of the complexes indicate that the variation of densities and the extent of charge transfers upon complexation correlate well with the obtained interaction energies.     

Primary photophysical and photochemical processes for Pt(SCN)<Subscript>6</Subscript><Superscript>2–</Superscript> complex

Photosolvation of a Pt^IV hexathiocyanate complex Pt(SCN)₆ ^2– in water and ethanol was studied by steady-state photolysis, nanosecond laser flash photolysis, and ultrafast kinetic spectroscopy. Complexes Pt(SCN)₅(H₂O)^– and Pt(SCN)₅(C₂H₅OH)^– were found to be the only reaction products. The quantum yields of photosolvation are independent of the excitation wavelength, being equal to 0.25 and 0.5 for the solutions of the complex in water and ethanol, respectively. Photosolvation proceeds by the mechanism of heterolytic metal—ligand bond dissociation without involvement of redox processes. The characteristic time of formation of the end products for both solvents is about 10 ps. Three successive intermediates detected on the picosecond time scale were interpreted as Pt^IV complexes. The nature of the intermediates and possible mechanisms of photosolvation are discussed.     

Experimental and theoretical characterization of Fe<Subscript>2</Subscript>Cr trinuclear-oxo-centered complex with a CF<Subscript>2</Subscript>ClCOO<Superscript>–</Superscript> bridge

In this work, an atrinuclear-oxo-centered complex of the CrFe₂ type with the CF₂ClCOO^– bridging ligand is newly synthesized. The complex is characterized by experimental and theoretical methods. The optimized geometry and theoretical vibrational frequencies are computed using the density functional theory (DFT) method. Also, the AIM analysis was applied to study changes in topological parameters such as the electron density at critical points of all the bonds of the complex. In the optimized geometry of the complex, three metal ions form a trigonal-planar structure with a μ₃-O atom in its center. Each of M³⁺ metal ions has an octahedral coordination environment of oxygen atoms. The DFT results are in agreement with the experimental ones, confirming the validity of the optimized geometry for the complex.     

Sb(III) fluoride complexes with DL-valine. Crystal structure of molecular complex SbF<Subscript>3</Subscript>{(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>CHCH(<Superscript>+</Superscript>NH<Subscript>3</Subscript>)COO<Superscript>−</Superscript>}

Preparative method in combination with X-ray diffraction and IR spectroscopy is used to study reaction of Sb(III) fluoride with -aminoisovaleric acid (DL-valine) in an aqueous solution in the range of the molar ratios of components (0.25–2) : 1 in the presence of hydrofluoric acid. The molecular complex of Sb(III) fluoride with valine (1 : 1) of the composition SbF₃{(CH₃)₂CHCH(⁺NH₃)COO^–}(I) and valinium tetrafluoro-antimonate(III) monohydrate {(CH₃)₂CHCH(₊NH₃)COOH}SbF₄· H₂O (II) are synthesized for the first time. Crystal structure was determined for the molecular complex I consisting of SbF₃ groups and valine molecules united into polymer chains through bidentate bridging carboxylate groups of amino acid molecules.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 2, 2005, pp. 125–131.Original Russian Text Copyright © 2005 by Zemnukhova, Davidovich, Udovenko, Kovaleva.