Influence of ion size on the stability of chloroplumbates containing PbCl<Stack><Subscript>5</Subscript><Superscript>−</Superscript></Stack> or PbCl<Stack><Subscript>6</Subscript><Superscript>2−</Superscript></Stack>

The enthalpies of formation of PbCl₄, PbCl₅⁻ and PbCl₆²⁻, originating from quantum mechanics, have enabled the thermodynamic behaviour of these ions with respect to Cl-detachment to be assessed. The stability of salts containing PbCl₅⁻ and PbCl₆²⁻ as a function of the dimensions of these anions and complementary cations was studied using an approach combining the Kapustinskii-Yatsimirskii equation with basic thermochemical relationships. It was found that hexachloroplumbates of monovalent metal cations will not dissociate into metal chlorides and PbCl₄, provided the complementary cations are suitably large in size. Hexachloroplumbates of divalent metal cations have not yet been synthesised since no known metal cations attain the requisite large size. Such salts will not dissociate if the divalent metal cations are able to complex suitably large electron-donating ligands. The pentachloroplumbates of both monovalent and divalent metal cations are unstable, since no known metal cations have appropriately large ionic radii. The approach adopted appears to be useful for the examination of the thermal behaviour, stability and reactivity of chloroplumbates.     

Chemical Bonding in the Complexes XeF<Stack><Subscript>5</Subscript><Superscript>+</Superscript></Stack>XF<Stack><Subscript>6</Subscript><Superscript>−</Superscript></Stack> (X = P,As, Sb,and Bi)

Ab initio quantum-chemical calculations of the complexes XeF ₅ ⁺ XF ₆ ^? (X = P, As, Sb, and Bi) were performed with the use of relativistic pseudopotentials for heavy atoms and full-electron basis sets. The chemical bonds were characterized by the parameters of critical points (electron density, its Laplacian, total electron energy, and its kinetic and potential components). It was demonstrated that the interaction between the XeF ₅ ⁺ cation and the XF ₆ ^? anion in XeF ₅ ⁺ XF ₆ ^? follows a key-lock scheme involving directed interactions of bridging fluorine atoms F_b → Xe and that the structuring function of the lone electron pair of the Xe atom is to compensate the destabilizing electrostatic interaction between the Xe and X atoms bearing excess positive charges.     

Mercury complex [(HOCH<Subscript>2</Subscript>)<Subscript>3</Subscript>CNH<Subscript>3</Subscript>]<Stack><Subscript>2</Subscript><Superscript>+</Superscript></Stack> [HgI<Subscript>4</Subscript>]<Superscript>2−</Superscript>: Synthesis and structure

The complex [(HOCH₂)₃CNH₃] ₂ ⁺ [HgI₄]^2? (I) was synthesized by reacting (trioxymethyl)methylammonium iodide with mercury dioide (2: 1 mol/mol) in acetone. X-ray crystallography shows that the complex consists of two types of crystallographically independent [(HOCH₂)₃CNH₃]⁺ cations and tetrahedral anions [HgI₄]^2? (IHgI, 106.49(2)°–113.99(4)°; Hg-I, 2.7849(8)-2.8105(8) Å. [(HOCH₂)₃CNH₃]⁺ cations are linked via hydrogen bonds O…H-N and O-H…N (O…N, 2.84–2.92 Å) to form polymer chains, which are cross-linked with one another via anions (I…H, 2.81, 2.82 Å).     

Hydration of CBr<Subscript>3</Subscript>COOH molecules and CBr<Subscript>3</Subscript>CO<Stack><Subscript>2</Subscript><Superscript>–</Superscript></Stack> anions in aqueous solutions

The optimal structures and the vibrational frequencies of H-bonded complexes formed from one-two CBr₃COOH molecules or the CBr₃CO ₂ ^– anion with water molecules are calculated by density functional theory (B3LYP/6-31++G(d,p)). The comparison of the obtained results with the known Raman spectra of the CBr₃COOH–H₂O and NaCBr₃CO ₂ ^– ·H₂O solutions (with component molar ratios of ≤1:16) shows that they include stable hydrates: CBr₃COOH·H₂O and CBr₃CO ₂ ^– ·(H₂O)₆. The first one has a cyclic form, and the second has a cubic globular form. The vibrational band frequencies of the CBr₃COOH molecule and the CBr₃CO ₂ ^– anion in the spectra of both solutions are almost completely determined by the mutual arrangement of units in these hydrates.     

Synthesis and Structure of the bismuth complex [Ph<Subscript>3</Subscript>PrP]<Stack><Subscript>4</Subscript><Superscript>+</Superscript></Stack>[Bi<Subscript>4</Subscript>I<Subscript>16</Subscript>]<Superscript>4−</Superscript>

The complex [Ph₃P] ₄ ⁺ [Bi₄I₁₆]^4? · 2 Me₂C=O (I) was synthesized by the reaction of triphenyl(propyl)phosphonium iodide with bismuth iodide in acetone. The crystal structure of complex I was determined by X-ray crystallography. It contains, in addition to solvent molecules, two types of crystallographically independent tetrahedral tetraphenyl(propyl)phosphonium cations and tetranuclear anions [Bi₄I₁₆]^4? in a chair conformation with the bismuth atoms being in an octahedral coordination. The Bi-I distances in the anion vary within 2.8768(4)–3.2524(4) Å.     

Synthesis and physicochemical study of the PMo<Subscript>11</Subscript>(TiO)O<Stack><Subscript>39</Subscript><Superscript>5−</Superscript></Stack> heteropolyanion

Procedures were developed for the synthesis of the guanidinium (Gua) and tetrabutylammonium (TBA) salts of 11-molybdotitano(IV)phosphate heteropolyanion (MTPH) from solutions with the stoichiometric ratio P: Mo = 1: 11 and in excess of titanium(IV) ions, Ti: P ≥ 1.5, at pH 1.85–1.90. MTPH was isolated as the (Gua)₅PMo₁₁(TiO)O₃₉ and (TBA)₅PMo₁₁(TiO)O₃₉ salts. The composition and formula of MTPH were established by chemical analysis, electronic absorption spectroscopy in the visible region of the oxidized and reduced MTPH forms, IR spectroscopy, and ³¹P NMR. H₅PMo₁₁(TiO)O₃₉, obtained by ion exchange of the Gua salt in an aqueous-organic medium, is a strong pentabasic acid. MTPH reacts with H₂O₂ to form a peroxo complex with limited stability in an aqueous solution. In aqueous-organic media, the peroxo complex is more stable. In acetonitrile, MTPH persists for several days.     

Reactions of [NH<Stack><Subscript>3</Subscript><Superscript>+·</Superscript></Stack>, H<Subscript>2</Subscript>O] with carbonyl compounds: A McLafferty rearrangement within a complex?

The reactions of the water solvated ammonia radical cation [NH(3)(+*), H(2)O] with a variety of aldehydes and ketones were investigated. The reactions observed differ from those of low energy aldehydes and ketones radical cations, although electron transfer from the keto compound to ionized ammonia is thermodynamically allowed within the terbody complexes initially formed. The main process yields an ammonia solvated enol with loss of water and an alkene. This process corresponds formally to a McLafferty fragmentation within a complex. With aldehydes, another reaction can take place, namely the transfer of the hydrogen from the CHO group to ammonia, leading to the proton bound dimer of ammonia and water, and to the NH(4)(+) cation. Comparison between the available experimental results leads to the conclusion that the McLafferty fragmentation occurs within the terbody complex initially formed, with no prior ligand exchange, the water molecule acting as a spectator partner.     

The effect of NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack> and OH<Superscript>−</Superscript> ions on the laser ablation of Cs<Superscript>+</Superscript> ion on Type 304 stainless steel

Type 304 stainless steel specimens artificially contaminated with CsCl solution were treated with KOH solution and KNO₃ solution, respectively. Cs⁺ ion removal tests by a Q-switched Nd:YAG laser at 1064 nm at a given fluence of 57.3 J/cm² were performed. The surface morphology and the relative atomic mole ratio of the specimen surface were investigated by SEM and EPMA. The order of Cs⁺ ion removal efficiency of laser was no-treatment < KOH < KNO₃ during the 42 shots. From the investigation of XPS peaks around 532.7 and 292.9 eV, KNO₃ on a surface of specimen was found to be fully decomposed during the laser irradiation. It was suggested that Cs₂O particulates formed by the reaction between the reactive oxygen generated from the nitrate ion and Cs⁺ ion on the metal surface could be easily suspended. For the KOH system, FeOOH was formed during the laser irradiation and it changed into Fe₂O₃. It was also suggested that Cs₂O particulates were formed by the reaction between the reactive oxygen generated from the decomposition of K₂O and Cs⁺ ion on the metal surface..     

Stable cyclopentadienyl-type fullerenyl radical Me<Subscript>5</Subscript>C<Stack><Subscript>60</Subscript><Superscript>•</Superscript></Stack>: experimental detection by EPR spectroscopy and quantum chemical calculations

A paramagnetic compound was detected in the synthesis of a hydride (Me)₅C₆₀H with an isolated cyclopentadienyl ring. The EPR spectrum of this compound corresponds to free radical (Me)₅C₆₀• with nonequivalent Me-group protons. The structure of the radical was confirmed by quantum chemical calculations. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1597–1599, August, 2008.     

Identification of Anionic Supramolecular Complexes of Sulfonamide Receptors with Cl<Superscript>−</Superscript>, NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack>, Br<Superscript>−</Superscript>, and I<Superscript>−</Superscript> by APCI-MS

As part of a mass spectrometric investigation of the binding properties of sulfonamide anion receptors, an atmospheric pressure chemical ionization mass spectrometric (APCI-MS) method involving direct infusion followed by thermal desorption was employed for identification of anionic supramolecular complexes in dichloromethane (CH₂Cl₂). Specifically, the dansylamide derivative of tris(2-aminoethyl)amine (tren) (1), the chiral 1,3-benzenesulfonamide derivatives of (1R,2S)-(+)-cis-1-amino-2-indanol (2), and (R)-(+)-bornylamine, (3), were shown to bind halide and nitrate ions in the presence of (n−Bu)₄N⁺X⁻ (X⁻ = Cl⁻, NO₃⁻, Br⁻, I⁻). Solutions of receptors and anions in CH₂Cl₂ were combined to form the anionic supramolecular complexes, which were subsequently introduced into the mass spectrometer via direct infusion followed by thermal desorption. The anionic supramolecular complexes [M+X]⁻, (M=1–3, X⁻=Cl⁻, NO₃⁻, Br⁻, I⁻) were observed in negative mode APCI-MS along with the deprotonated receptors [M−H]⁻. Full ionization energy of the APCI corona pin (4.5 kV) was necessary for obtaining mass spectra with the best signal-to-noise ratios.     

Isothermal solubility diagram of the 2Na<Superscript>+</Superscript>,Mg<Superscript>2+</Superscript>‖2Cl<Superscript>−</Superscript>, 2ClO<Stack><Subscript>3</Subscript><Superscript>‒</Superscript></Stack>-H<Subscript>2</Subscript>O quaternary system at 20 and 100°C

The solubility in the 2Na⁺,Mg²⁺‖2Cl⁻, 2ClO₃⁻-H₂O system was studied at 20 and 100°C and the solubility diagrams were plotted. New compounds were not found to form in the title quaternary reciprocal system. The sodium chloride field was observed to expand with rising temperature.     

A New Sandwich Polyoxometalate Constructed from a Zn<Stack><Subscript>6</Subscript><Superscript>12+</Superscript></Stack> Hexagon Cluster Sandwiched by Two B-α-[BiW<Subscript>9</Subscript>O<Subscript>33</Subscript>]<Superscript>9−</Superscript>

A new sandwich polyoxometalate Na₄Zn₂[Zn₂(H₂O)₁₀(ZnCl)₆(B-α- BiW₉O₃₃)₂] · 40.5H₂O (1) has been obtained in aqueous solution and characterized by IR, UV, element analysis, TG and single-crystal X-ray analysis. Polyoxoanion 1 is composed of a Zn ₆ ¹²⁺ hexagon sandwiched by two [BiW₉O₃₃]^9? units, which is firstly observed in tungstobismutate. The crystal data for compound 1: Triclinic, space group P–1, a = 15.426(3) Å, b = 15.467(3) Å, c = 15.526(3) Å, α = 74.24(3)°, β = 64.37(3)°, γ = 60.73(3)°, V = 2905.3(1) ų, Z = 1.     

The structure of deprotonated tri-alanine and its <Emphasis Type="Italic">a</Emphasis><Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack> fragment anion by IR spectroscopy

We present the first infrared spectra of a mass-selected deprotonated peptide anion (AlaAlaAla) and its decarboxylated fragment anion formed by collision induced dissociation. Spectra are obtained by IRMPD spectroscopy using an FTICR mass spectrometer in combination with the free electron laser FELIX. Spectra have been recorded over the 800–1800 cm⁻¹ spectral range and compared with density functional theory calculated spectra at the B3LYP/6-31++G(d,p) level for different isomeric structures. These experiments suggest a carboxylate anion for [M-H]⁻ and an amide deprotonated (amidate) structure for the a ₃ fragment anion [M-H-CO₂]⁻. The frequency for the amidate carbonyl stretch occurring around 1555±5 cm⁻¹ has been confirmed by additional spectroscopic studies of the conjugated base of N-methylacetamide, which serves as a simple model system for the deprotonated amide linkage in a peptide anion.     

Spectrophotometric study of Eu<Superscript>+</Superscript> + H<Subscript>2</Subscript>O ↔ EuOH<Superscript>+</Superscript> + H equilibrium in flames with europium additions

Using the third law of thermodynamics, we found the enthalpy Δ_r H ^o(0) = 71 ± 7 of the reaction Eu⁺ + H₂O ↔ EuOH⁺ + H and the binding energies D ₀(Eu⁺-OH) = 423 ± 7 and D ₀(Eu-OH) = 389 ± 11 (kJ/mol). To determine the latter, we additionally used the ionization potential I ₀(EuOH) = 5.32 ± 0.08 eV found using the Stark intramolecular effect.     

Nongeneral Character of the Resonance Parameters Σ<Stack><Subscript>R</Subscript><Superscript>+</Superscript></Stack> of Silicon-, Germanium-, and Tin-Containing Substituents in Radical Cations

The resonance parameters σ _R ⁺ of substituents Y in radical cations YD^+· [where D is a π- or n-type center, and Y = MMe₃, CH₂MMe₃ (M = Si, Ge, Sn), C(SiMe₃)₃] depend on the nature of both Y and D. Using radical cations YD^+· (Y = CH₂SiMe₃, SnMe₃) as examples, it was found that the two conjugation parameters, constants σ _R ⁺ of substituents Y and perturbation energy calculated by the modified molecular orbital perturbation method, are linearly related to each other. The energies of donor and acceptor components of the overall resonance effect of CH₂SiMe₃ and SnMe₃ with respect to radical cation centers D^+· were estimated for the first time. The donor energy constituent in YD^+· is considerably greater than in neutral DY molecules.     

Theoretical study of the activation barriers of elementary reactions of hydrogenation of aluminide clusters X@Al<Subscript>12</Subscript> and X@Al<Stack><Subscript>12</Subscript><Superscript>−</Superscript></Stack> with dopants X = Al,Si, and Ge

The transition states and activation barriers h of elementary reactions of addition of the H₂ molecule to aluminide clusters Al₁₃, Al ₁₃ ^? , Al₁₃H ₂ ^? , Al₁₃H ₄ ^? , Si@Al₁₂, Ge@Al₁₂, and LiAl₁₃ were calculated within the B3LYP approximation of the density functional theory using 6–31G* and 6–311+G* basis sets. The barriers h for all diamagnetic clusters were found to be high (～30–40 kcal/mol). The outer-sphere cation Li⁺ decreases while the endohedral electronegative dopants Si and Ge increase the barrier by a few kcal/mol. The hydrogenation barrier of the neural paramagnetic cluster Al₁₃, which has free valence, decreases to ～20 kcal/mol. The addition of a hydrogen atom or a Cl₂ molecule to both paramagnetic and diamagnetic aluminum clusters occurs without a barrier. The first stage of the reaction (addition of H₂ to an Al-Al edge) is in all cases the critical stage of aluminide hydrogenation. The barrier h of this reaction is several times higher than the barriers to migration of hydrogen atoms over the metal cage. The migration of H atoms occurs simultaneously with considerable distortions of the Al₁₃ cage even to the extent that it changes its structural motif. The addition of the H₂ molecule to the Al@TiAl₁₁ cluster containing the peripheral titanium atom occurs with a small barrier, whereas the barrier to elimination of H₂ from the dihydride Al@TiAl₁₁H₂ is reduced to ～15 kcal/mol. Based on the calculations, the conclusion was drawn that the elementary reactions of hydrogenation and dehydrogenation for Ti-doped aluminide clusters should occur considerably faster and under milder conditions than for homonuclear aluminides.     

A study of the hydrolysis of ZrF<Stack><Subscript>6</Subscript><Superscript>2−</Superscript></Stack> and the structure of intermediate hydrolysis products by <Superscript>19</Superscript>F and <Superscript>91</Superscript>Zr NMR in the 9.4 T field

The high-field ¹⁹F and ⁹¹Zr NMR method is used to study the hydrolysis and polycondensation of hexafluorozirconate ZrF₆²⁻ in aqueous and water-peroxide solutions. During hydrolysis in aqueous solutions only ZrF₆²⁻ and F⁻ ions were observed by NMR, however, in the water-peroxide medium, an intermediate product of hydrolysis ([F₅Zr-OO-ZrF₅]⁴⁻ dimer) was detected. The dimer structure is confirmed by ¹⁹F and ⁹¹Zr NMR. In high fields (¹⁹F NMR frequency > 200 MHz), the fluorine exchange between ZrF₆²⁻ and F⁻ is slow in the ¹⁹F NMR scale and has a multisite character.     

Formation of (b<Subscript><Emphasis Type="Italic">n</Emphasis>−1</Subscript> + H<Subscript>2</Subscript>O) ions by collisional activation of maldi-formed peptide [M + H]<Superscript>+</Superscript> ions in a QqTOF mass spectrometer

Collisional activation of [M + H](+) parent ions from peptides of n amino acid residues may yield a rearrangement that involves loss of the C-terminal amino acid residue to produce (b(n-1) + H(2)O) daughters. We have studied this reaction by a retrospective examination of the m/z spectra of two collections of data. The first set comprised 398 peptides from coat protein digests of a number of plant viruses by various enzymes, where conditions in the tryptic digests were chosen so as to produce many missed cleavages. In this case, a large effect was observed-323 (b(n-1) + H(2)O) daughter ions (approximately 81%), including 185 (approximately 46%) "strong" decays with ratios (b(n-1) + H(2)O)/(b(n-1)) > 1. The second set comprised 1200 peptides, all from tryptic digests, which were carried out under more stringent conditions, resulting in relatively few missed cleavages. Even here, 190 (b(n-1) + H(2)O) ions (approximately 16%) were observed, including 87 (> 7%) "strong" decays, so the effect is still appreciable. The results suggest that the tendency for (b(n-1) + H(2)O) ion formation is promoted by the protonated side chain of a non-C-terminal basic amino acid residue, in the order arginine > lysine > or = histidine, and that its (non-C-terminal) position is not critical. The results can be interpreted by a mechanism in which hydrogen bonding between the protonated side chain and the (n - 1) carbonyl oxygen facilitates loss of the C-terminal amino acid residue to give a product ion having a carboxyl group at the new C-terminus.     

Gas Chromatographic-Ion Trap Mass Spectrometric Analysis of Volatile Organic Compounds by Ion–Molecule Reactions Using the Electron-Deficient Reagent Ion CCl<Stack><Subscript>3</Subscript><Superscript>+</Superscript></Stack>

When using tetrachloromethane as the reagent gas in gas chromatography-ion trap mass spectrometry equipped with hybrid ionization source, the cation CCl₃⁺ was generated in high abundance and further gas-phase experiments showed that such an electron-deficient reagent ion CCl₃⁺ could undergo interesting ion–molecule reactions with various volatile organic compounds, which not only present some informative gas-phase reactions, but also facilitate qualitative analysis of diverse volatile compounds by providing unique mass spectral data that are characteristic of particular chemical structures. The ion–molecule reactions of the reagent ion CCl₃⁺ with different types of compounds were studied, and results showed that such reactions could give rise to structurally diagnostic ions, such as [M + CCl₃ – HCl]⁺ for aromatic hydrocarbons, [M – OH]⁺ for saturated cyclic ether, ketone, and alcoholic compounds, [M – H]⁺ ion for monoterpenes, M^·+ for sesquiterpenes, [M – CH₃CO]⁺ for esters, as well as the further fragment ions. The mechanisms of ion–molecule reactions of aromatic hydrocarbons, aliphatic ketones and alcoholic compounds with the reagent ion CCl₃⁺ were investigated and proposed according to the information provided by MS/MS experiments and theoretical calculations. Then, this method was applied to study volatile organic compounds in Dendranthema indicum var. aromaticum and 20 compounds, including monoterpenes and their oxygen-containing derivatives, aromatic hydrocarbon and sesquiterpenes were identified using such ion–molecule reactions. This study offers a perspective and an alternative tool for the analysis and identification of various volatile compounds.     

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.