Vibrational spectra of X2O7n− anions

A careful study of the Raman spectra of aqueous solutions containing X₂O₇ⁿ⁻ anions, where X = P, n = 4; X = Cr or Se, n = 2, has shown for the first time that in all cases the δX-O-X bending mode occurs below 100 cm⁻¹. In addition, further information on the XO₃ terminal stretches was obtained from FTIR spectra of the aqueous solutions. Consequently, more realistic vibrational assignments were obtained for these frequently-studied inorganic anions.     

Reactions of CH3SH and CH3SSCH3 with gas-phase hydrated radical anions (H2O)n(•-), CO2(•-)(H2O)n, and O2(•-)(H2O)n

The chemistry of (H(2)O)(n)(?-), CO(2)(?-)(H(2)O)(n), and O(2)(?-)(H(2)O)(n) with small sulfur-containing molecules was studied in the gas phase by Fourier transform ion cyclotron resonance mass spectrometry. With hydrated electrons and hydrated carbon dioxide radical anions, two reactions with relevance for biological radiation damage were observed, cleavage of the disulfide bond of CH(3)SSCH(3) and activation of the thiol group of CH(3)SH. No reactions were observed with CH(3)SCH(3). The hydrated superoxide radical anion, usually viewed as major source of oxidative stress, did not react with any of the compounds. Nanocalorimetry and quantum chemical calculations give a consistent picture of the reaction mechanism. The results indicate that the conversion of e(-) and CO(2)(?-) to O(2)(?-) deactivates highly reactive species and may actually reduce oxidative stress. For reactions of (H(2)O)(n)(?-) with CH(3)SH as well as CO(2)(?-)(H(2)O)(n) with CH(3)SSCH(3), the reaction products in the gas phase are different from those reported in the literature from pulse radiolysis studies. This observation is rationalized with the reduced cage effect in reactions of gas-phase clusters.     

Rate constants of atomic hydrogen formation in H3O+(H2O) n + e → H + (H2O) n gas-phase processes

Using the Maxwellian electron velocity distribution and the Breit-Wigner approximation of the reaction cross section, the kinetic parameters of the hydrogen atom formation upon the electron capture by positively charged hydronium-water clusters are estimated. Calculations of the cross sections and rate constants are based on the data of quantum chemical studies of H₃O⁺(H₂O) _n and H₃O(H₂O) _n clusters, particularly on the detailed analysis of the spacing of high-lying states of the radicals and the character of the unpaired electron density distribution, as well as on the general trend in the electron affinity change of the cations depending on the number of water molecules. The lifetimes of the radicals before the dissociation are taken from the classical nonempirical molecular dynamics runs. The results are compared to available experimental data. The article is published in the original.     

Density functional investigations on the (H2O)n·CCH and (H2O)n·HCC complexes (n=1–3)

The electronic structures and energies of (H₂O)_n·CCH and (H₂O)_n·HCC complexes (n=1–3) between CCH and water have been theoretically investigated at the UB3LYP/6-311++G(2df,p)//UB3LYP/6-311G(d,p) level. The complexes with n=2–3 are cyclic structures with homodromic hydrogen-bond chain. The (H₂O)_n·CCH (n=1–3) complexes show increasing stabilities towards CCH- or H₂O-eliminations of 2.3, 5.8 and 7.6 kcal/mol and are energetically more stable than the corresponding (H₂O)_n·HCC complexes by 0.8, 2.7 and 3.4 kcal/mol, respectively, due to the charge-separation-enhanced hydrogen bonds within (H₂O)_n·CCH (n=2,3). Strong interactions between CCH and (H₂O)₂ and (H₂O)₃ clusters suggest special solvent effects of water on the chemical behavior of unsaturated radicals.     

Magneli phase Ti n O2n − 1 as corrosion-resistant PEM fuel cell catalyst support

Magneli phase titanium suboxide, Ti _n O_{2n ? 1}, with Brunauer–Emmett–Teller surface area up to 25 m² g^?1 was prepared using the heat treatment of titanium oxide (rutile) mixed with polyvinyl alcohol in ratios from 1:3 to 3:1. XRD patterns showed Ti₄O₇ as the major phase formed during the heat treatment process. The Ti _n O_{2n ? 1} showed excellent electrochemical stability in the potential range of ?0.25 to 2.75 V vs. standard hydrogen electrode. The Ti _n O_{2n ? 1} was employed as a polymer electrolyte membrane fuel cell catalyst support to prepare 20 wt% platinum (Pt)/Ti _n O_{2n ? 1} catalyst. A fuel cell membrane electrode assembly was fabricated using the 20 wt% Pt/Ti _n O_{2n ? 1} catalyst, and its performance was evaluated using H₂/O₂ at 80 °C. A current density of 0.125 A?cm^?2 at 0.6 V was obtained at 80 °C.     

Theoretical study of [Ni (H2O)n]2+(H2O)m (n ≤ 6, m ≤ 18)

The [Ni-(H(2)O)(n)](2+)(H(2)O)(m) (n ≤ 6, m ≤ 18) complexes were studied by means of first-principles all-electron calculations performed with the BPW91 gradient corrected functional and the 6-311+G(d,p) basis sets for the H, O, and Ni atoms. Triplet states were found as low-lying states for each (n, m) combination. The estimated Ni(2+)-(H(2)O)(n) binding energies (112.8-57.4 kcal/mol for the first layer and 52.0-23.0 kcal/mol for the second one) decreases and the Ni(2+)-OH(2) bond lengths lengthen as n + m increases. With six H(2)O moieties the Ni(2+) ion furnishes its first coordination sphere of octahedral geometry. Further water addition renders the formation of the second layer. The effect of Ni(2+) on the (H(2)O)(n)···(H(2)O)(m) hydrogen bond formation for several "n" and "m" combinations was studied, revealing an enhancement of this kind of bonding, which is of key importance for the stabilization and growth of the clusters. For some n + m isomers the second layer appears before the first octahedral layer is fully formed. For example, the square planar Ni(2+)-(H(2)O)(4) core originates two-dimensional 4 + 2 and 4 + 4 isomers, where each outer water molecule accepts two H-bonds, lying 2.0 kcal/mol above the 6 and 6 + 2 ground states. The clusters were also studied by IR spectra; the OH stretching vibrational frequencies allowed us to identify the outer solvation shells by the presence of red-shifted hydrogen bond regions.     

Gas phase reactions of Cl2O with X−(D2O)n=0–4 (X = O,OD, O2, DO2, and O3)

The reactions of Cl₂O with the cluster ions X⁻(D₂O)_n=0–4 (X = O, OD, O₂, DO₂, and O₃) were studied in a He buffer gas at temperatures within the range 171–298 K and pressures of 0.27–0.51 Torr, using a flow-tube apparatus. All ions were found to react with Cl₂O at rates slower than predicted by the collision rate and the charge center was transferred from X⁻ to Cl⁻ or ClO⁻. The primary product ions Cl⁻(DOCl) and ClO⁻(DOCl) were observed to react further to produce the ions Cl₃O⁻ and Cl₃O₂⁻. The rate constants for the observed reactions are reported and the role that thermodynamics plays in determining possible reaction channels is discussed.     

Polymeric (NO)3(N2O) n , (NO)3(N2O) n + , and (NO)3(N2O) n − : an interpretation of experimental observations

Semi-empirical and ab initio calculations are reported which provide a possible explanation for reported experimental results on 2-photon ionization of NO containing a few percent of N₂O, which found (NO)₃(N₂O) _n ^+or? clusters to be significantly more abundant than other (NO) _m (N₂O) _n products. It is found that the observed abundances of (NO)₃(N₂O) _n ionic clusters may be accounted for by the existence of covalent cyclic trimers of nitric oxide attached to oligomers of nitrous oxide. The extra stability of NO trimers in the observed clusters appears to arise from (NO) ₃ ⁺ rather than (NO)₃. Attachment of an (N₂O) _n side chain to (NO) ₃ ⁺ occurs exothermically. It is suggested that the addition of N₂O to cyclic-(NO) ₃ ⁺ might provide a means of making a polymer of nitrous oxide, which could have useful properties.     

Production of doubly charged clusters (H2O)n · Ba2+ and (H2O)n · Ca2+ under low temperature fast atom bombardment conditions

Production of doubly charged ions of alkaline earth metals Ba²⁺ and Ca²⁺ and their doubly charged clusters with water molecules (H₂O)_n · Ba²⁺, (H₂O)_n · Ca²⁺ (n = 1, 2, 3) by means of low temperature fast atom bombardment technique is observed in the case of crystalline hydrates of BaCl₂ and CaCl₂ salts, formed during freezing of water-salt solutions. Reasons for a possibility of production of the doubly charged species in the case of the two indicated salts and their absence in the case of chlorides of some other divalent metals (Mg, Mn, Co, Cu, Zn) are discussed. As to singly charged secondary ions Me⁺, MeCl⁺, MeOH⁺, [(H₂O)_n · MeCl]⁺, [(H₂O)_n · MeOH]⁺ (where Me is metal), high efficiency of their production from crystalline hydrates was observed and possible explanation of the phenomenon is suggested.     

Infrared Spectroscopy of Size-Selected Hydrated Carbon Dioxide Radical Anions CO2.−(H2O)n (n=2–61) in the C−O Stretch Region

Understanding the intrinsic properties of the hydrated carbon dioxide radical anions CO₂^.−(H₂O)_n is relevant for electrochemical carbon dioxide functionalization. CO₂^.−(H₂O)_n (n=2–61) is investigated by using infrared action spectroscopy in the 1150–2220 cm⁻¹ region in an ICR (ion cyclotron resonance) cell cooled to T=80 K. The spectra show an absorption band around 1280 cm⁻¹, which is assigned to the symmetric C−O stretching vibration ν_s. It blueshifts with increasing cluster size, reaching the bulk value, within the experimental linewidth, for n=20. The antisymmetric C−O vibration ν_as is strongly coupled with the water bending mode ν₂, causing a broad feature at approximately 1650 cm⁻¹. For larger clusters, an additional broad and weak band appears above 1900 cm⁻¹ similar to bulk water, which is assigned to a combination band of water bending and libration modes. Quantum chemical calculations provide insight into the interaction of CO₂^.− with the hydrogen-bonding network.     

Syntheses and crystal structures of two Cd(II) coordination polymers: one-dimensional chain [Cd(C4H6N2)2(C4H2O4)(H2O)2] n and two-dimensional sheet [Cd(C4H6N2)(H2O)(C4H4O4)] n · n H2O

Two new Cd(II) coordination polymers, [Cd(C₄H₆N₂)₂(C₄H₂O₄)(H₂O)₂] _n (1) (where C₄H₆N₂?=?2-methylimidazole, C₄H₂O₄?=?fumarate), and [Cd(C₄H₆N₂)(H₂O)(C₄H₄O₄)] _n ?·?nH₂O (2), (where C₄H₄O₄?=?succinates), have been prepared and structurally characterized by single crystal X-ray diffraction. Complex 1 crystallizes in the triclinic space group P 1 in a one-dimensional chain structure, in which carboxy is monodentate; a three-dimensional supermolecular network structure was formed through hydrogen bonding. In complex 2, the coordination geometry of the Cd atoms is a pentagonal bipyramid, and a two-dimensional sheet is formed though carboxyl group bridging. In 1 and 2, IR spectra indicate the presence of bridging carboxyl groups, confirmed by structure analyses.     

Hydrated magnesium cations Mg+(H2O)n, n ≈ 20-60, exhibit chemistry of the hydrated electron in reactions with O2 and CO2

Ion-molecule reactions of Mg(+)(H(2)O)(n), n ≈ 20-60, with O(2) and CO(2) are studied by Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry. O(2) and CO(2) are taken up by the clusters. Both reactions correspond to the chemistry of hydrated electrons (H(2)O)(n)(-). Density functional theory calculations predicted that the solvation structures of Mg(+)(H(2)O)(16) contain a hydrated electron that is solvated remotely from a hexa-coordinated Mg(2+). Ion-molecule reactions between Mg(+)(H(2)O)(16) and O(2) or CO(2) are calculated to be highly exothermic. Initially, a solvent-separated ion pair is formed, with the hexa-coordinated Mg(2+) ionic core being well separated from the O(2)(?-) or CO(2)(?-). Rearrangements of the solvation structure are possible and produce a contact-ion pair in which one water molecule in the first solvation shell of Mg(2+) is replaced by O(2)(?-) or CO(2)(?-).     

Phase Behavior and Structural Properties of the Triton X − 100/n − C n H2n + 1OH/H2O System

ABSTRACT

In the Triton X ? 100/n-C_nH_2n + 1OH/H₂O system, the lamellar liquid crystalline region increases and the regions of O/W, W/O and bicontinuous microemulsion domains shrink, simultaneously, with the length of the chain in the unbranched aliphatic alcohol. In the O/W region, the Gibbs free energy for alcohol transfer from the water continuous phase to Triton X ? 100 micellar phase increases linearly with the chain length of alcohol. In the W/O region of the Triton X ? 100/n ? C_nH_2n + 1OH/n ? C₇ H₁₆/H₂O system, as the solubilized water content increases, the effective radius (R _e ), the inner water radius (R _W ), the thickness of the interfacial layer (L) and the average aggregation number ([nbar]) of the reverse micelles increase, whereas the total number (N _d ), the total interfacial area (A _d ) and the change of the standard free energy (Δ _c ? i G ⁰) for alcohol transfer from the oil continuous phase to the interfacial layer of the reverse micelles decrease; and with the longer chain alcohols, the values of R _e , R _W , L, and [nbar] all increase, while the Δ _c-i G⁰ value decreases drastically with increasing chain length. In the lamellar liquid crystalline region, increasing the alcohol chain length can increase the stability of the lamellar liquid crystalline domain. All the results show that the alcohols, n ? C _n H_2n + 1OH, can be used as cosurfactants in the nonionic surfactant system and function similarly as in ionic surfactant systems.     

H3+O和H3+O(H2O)n(n=1,2,3)阳离子振动力场和光谱频率的理论计算

本文利用多原子分子振动力场的模型势函法对H₃⁺O和H₃⁺O(H₂O)_n(n=1～3)阳离子的振动力场作了理论计算,并对其光谱频率进行了预测.H₃⁺O和H₉⁺O₄的振动频率的结果优于从头算梯度法的结果.本文首次给出了H₅⁺O₂、H₇⁺O₃伸缩振动频率的理论预测值.     

Photoelectron spectroscopy of (CO2)n(H2O) m − clusters

Photoelectron spectra of (CO₂)_nH₂O^? (2≤n≤8) and (CO₂)_n(H₂O) ₂ ^? (1≤n≤2) were measured at the photon energy of 3.49 eV. The spectra show unresolved broad features, which are approximated by Gaussians. The vertical detachment energies (VDEs) were determined as a function of the cluster size. For (CO₂)_nH₂O^?, the VDE-n plots exhibit a sharp discontinuity between n=3 and 4; the VDE value is ≈3.5 eV at n=3, while it drops down abruptly to 2.59 eV at n=4. This discontinuity in VDE is ascribed to "core switching" at n=4; a C₂O ₄ ^? dimer anion forms the core of (CO₂)_nH₂O^? for n≤3, while a monomer CO ₂ ^? is the core for n≥4. The (CO₂)₂(H₂O) ₂ ^? ion has a VDE of 2.33 eV, indicating the presence of a CO ₂ ^? monomer core in the binary clusters containing two H₂O molecules.     

Parameters of Li2O2 · H2O crystallization from the LiOH-H2O2-H2O ternary system

The decomposition kinetics of peroxide products contained in the liquid phase of the LiOH-H₂O₂-H₂O ternary system were studied, and the applicability of the solubility method to studying this system was demonstrated for hydrogen peroxide concentrations in the liquid phase from 2 to 6 wt % and temperatures of 21–33°C. The stabilizing influence of solid Li₂O₂ · H₂O on hydrogen peroxide decomposition was demonstrated. The temperature and concentration boundaries of existence were determined for the Li₂O₂ · H₂O phase, whose identity was verified by chemical analysis and qualitative X-ray powder diffraction analysis.     

n(H_2O)(n=1,2)在HO_2+NO→HNO_3反应中的催化机制研究

采用CCSD(T)/aug-cc-p VTZ//B3LYP/6-311+G(2df,2p)方法对n(H_2O)(n=0,1,2)参与HO_2+NO→HNO_3反应的微观机理和速率常数进行了研究.结果表明,由于水分子与HO_2形成的复合物(H_2O…HO_2,HO_2…H_2O)结合NO与水分子形成的复合物(NO…H_2O,ON…H_2O)的反应方式具有较高能垒和较低有效速率,其对HO_2+NO→HNO_3反应的影响远小于双体水(H_2O)2与HO_2(或NO)形成复合物然后再与另一分子反应物NO(或HO_2)的反应方式,因此n(H_2O)(n=1,2)催化HO_2+NO→HNO_3反应主要经历了HO_2…(H_2O)_n(n=1,2)+NO和NO…(H_2O)_n(n=1,2)+HO_22种反应类型.由于HO_2…(H_2O)_n(n=1,2)+NO反应的低能垒和高速率,HO_2…(H_2O)_n(n=1,2)+NO反应优于NO…(H_2O)_n(n=1,2)+HO_2反应.与此同时,由于计算温度范围内HO_2…H_2O+NO反应的有效速率常数比HO_2…(H_2O)2+NO反应对应的有效速率常数大了10~12数量级,可推测(H_2O)_n(n=1,2)催化HO_2+NO→HNO_3反应主要来自于单个水分子.此外,在216.7~298.6 K范围内水分子对HO_2+NO→HNO_3反应起显著的正催化作用,且随温度的升高有明显增大的趋势,在298.2 K时增强因子k'RW1/ktotal达到67.93%,表明在实际大气环境中水蒸气对HO_2+NO→HNO_3反应具有显著影响.     

Synthesis,crystal structure and magnetic properties of a 1D coordination polymer[Ni(phth)(phen)(H2O)] n · n H2O

A new one-dimensional coordination polymer [Ni(phth)(phen)(H₂O)] _n ?·?nH₂O was synthesized. The structure was determined by X-ray crystallography revealing that each nickel atom is five-coordinate bridged via phthalate ion to form a zigzag chain. The chains are further linked together via hydrogen-bonding interactions to construct a three dimensional supramolecular network. The magnetic properties of the complex show that there are weak antiferromagnetic interactions between Ni(II) centers.