Skin Bond Electron Relaxation Dynamics of Germanium Manipulated by Interactions with H2, O2, H2O,H2O2, HF,and Au

Although germanium performs amazingly well at sites surrounding hetero‐coordinated impurities and under‐coordinated defects or skins with unusual properties, having important impact on electronic and optical devices, understanding the behavior of the local bonds and electrons at such sites remains a great challenge. Here we show that a combination of density functional theory calculations, zone‐resolved X‐ray photoelectron spectroscopy, and bond order length strength correlation mechanism has enabled us to clarify the physical origin of the Ge 3d core‐level shift for the under‐coordinated (111) and (100) skin with and without hetero‐coordinated H₂, O₂, H₂O, H₂O₂, HF impurities. The Ge 3d level shifts from 27.579 (for an isolated atom) by 1.381 to 28.960 eV upon bulk formation. Atomic under‐coordination shifts the binding energy further to 29.823 eV for the (001) and to 29.713 eV for the (111) monolayer skin. Addition of O₂, HF, H₂O, H₂O₂ and Au impurities results in quantum entrapment by different amounts, but H adsorption leads to polarization.     

New Aquapentachlorochromate(III) Compounds: K2[CrCl5(H2O)] and (NH4)2[CrCl5(H2O)]

Synthesis and crystal structures of two new compounds, K₂[CrCl₅(H₂O)] ( I ) and (NH₄)₂[CrCl₅(H₂O)] ( II ) are reported. Both compounds were prepared from chromium(VI) salts by two different methods and reaction pathways of these syntheses are suggested. The crystal structures of these two aquapentachlorochromates(III) have been determined from three dimensional X‐ray data collected at low temperature, 173 K. The two structures are isomorphous and their unit cell dimensions are quite similar. They are orthorhombic, space groups Pnma, with Z = 4. Both structures are composed of [CrCl₅(H₂O)]^2? units held together by the counterion framework. The coordination around the chromium ion deviates from a regular octahedron due to the shorter equatorial chromium‐oxygen bond.     

Ab Initio H2O in Realistic Hydrophilic Confinement

A protocol for the ab initio construction of a realistic cylindrical pore in amorphous silica, serving as a geometric nanoscale confinement for liquids and solutions, is presented. Upon filling the pore with liquid water at different densities, the structure and dynamics of the liquid inside the confinement can be characterized. At high density, the pore introduces long‐range oscillations into the water density profile, which makes the water structure unlike that of the bulk across the entire pore. The tetrahedral structure of water is also affected up to the second solvation shell of the pore wall. Furthermore, the effects of the confinement on hydrogen bonding and diffusion, resulting in a weakening and distortion of the water structure at the pore walls and a slowdown in diffusion, are characterized.     

Molecular Structure and Properties of a Novel Acylhydrazone (C14H14O6N4)·HCON(CH3)2·2H2O

[N-(Propionic acid)] terephthalal acyl dihydrazone(H₄L) was synthesized and characterized by element analysis, IR, ¹H NMR and MS. The theoretical studies on H₄L were carried out at HF/6-31+G(d) and B3LYP/ 6-31+G(d) levels. The main decomposition stage of it was studied with IR track. The kinetic parameters[the apparent activation energy(E_a) and pre-exponential constant(A) of the first and second stages of decomposition reaction] were obtained by Kissinger and Ozawa’s methods. Furthermore, the antimicrobial activity of H₄L against wheat rust was investigated by spore sprout method.     

Simple Ligand Effects Switch a Hydrogenase Mimic between H2 and O2 Activation

Herein, we report a [NiRu] biomimetic system for O₂‐tolerant [NiFe]hydrogenases and demonstrate that electron donation to the [NiRu] center can switch the system between the activation of H₂ and O₂ through simple ligand effects by using hexamethylbenzene and pentamethylcyclopentadienyl ligands, respectively. Furthermore, we present the synthesis and direct observations of a [NiRu]–peroxo species, which was formed by the oxygenation of a Ni‐SIa model [NiRu] complex, that we propose as a biomimetic analogue of O₂‐bound species (OBS) of O₂‐tolerant [NiFe]hydrogenases. The [NiRu]–peroxo complex was fully characterized by X‐ray analysis, X‐ray photoelectron spectroscopy (XPS), mass spectrometry, and ¹H NMR spectroscopy. The OBS analogue was capable of oxidizing p‐hydroquinone and sodium borohydride to turn back into the Ni‐SIa model complex.     

Quantum Chemical Study of the Reactions between Pd+/Pt+ and H2O/H2S

The study of the reactions of water and hydrogen sulfide with palladium and platinum cations has been completed in this work, in both low‐ and high‐spin states. Our calculations predict that only the formation of platinum sulfide is exothermic (in both spin states), whereas for the remaining species the oxides and sulfides are found to be more reactive than their corresponding bare metal cations. An in‐depth analysis of the reaction paths leading to metal oxide and sulfide species is given, including various minima, and several important transition states. All results have been compared with existing experimental and theoretical data, and earlier works covering the reaction of nickel cation with water and hydrogen sulfide to observe the trends for the group 10 transition metals.     

Deuterium exchange in the systems of H2O+/H2O and H3O+/H2O

The reactions of H₂O⁺, H₃O⁺, D₂O⁺, and D₃O⁺ with neutral H₂O and D₂O were studied by tandem mass spectrometry. The H₂O⁺ and D₂O⁺ ion reactions exhibited multiple channels, including charge transfer, proton transfer (or hydrogen atom abstraction), and isotopic exchange. The H₃O⁺ and D₃O⁺ ion reactions exhibited only isotope exchange. The variation in the abundances of all ions involved in the reactions was measured over a neutral pressure range from 0 to 2 × 10⁻⁵ Torr. A reaction scheme was chosen, which consisted of a sequence of charge transfer, proton transfer, and isotopic exchange reactions. Exact solutions to two groups of simultaneous differential equations were determined; one group started with the reaction of ionized water, and the other group started with the reactions of protonated water. A nonlinear least-squares regression technique was used to determine the rate coefficients of the individual reactions in the schemes from the ion abundance data. Branching ratios and relative rate coefficients were also determined in this manner.A delta chi-squared analysis of the results of the model fitted to the experimental data indicated that the kinetic information about the primary isotopic exchange processes is statistically the most significant. The errors in the derived values of the kinetic information of subsequent channels increased rapidly. Data from previously published selected ion flow tube (SIFT) study were analyzed in the same manner. Rigorous statistical analysis showed that the statistical isotope scrambling model was unable to explain either the SIFT or the tandem mass spectrometry data. This study shows that statistical analysis can be utilized to assess the validity of possible models in explaining experimentally observed kinetic behaviors.     

A Theoretical Study of the Ion—Molecule Chemistry of K+×X Complexes (X: O,O2, N2, CO2, H2O): Implications for the Upper Atmosphere.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

Crystal structures of hydrates of simple inorganic salts. II. Water‐rich calcium bromide and iodide hydrates: CaBr2·9H2O,CaI2·8H2O,CaI2·7H2O and CaI2·6.5H2O

Single crystals of calcium bromide enneahydrate, CaBr₂·9H₂O, calcium iodide octahydrate, CaI₂·8H₂O, calcium iodide heptahydrate, CaI₂·7H₂O, and calcium iodide 6.5‐hydrate, CaI₂·6.5H₂O, were grown from their aqueous solutions at and below room temperature according to the solid–liquid phase diagram. The crystal structure of CaI₂·6.5H₂O was redetermined. All four structures are built up from distorted Ca(H₂O)₈ antiprisms. The antiprisms of the iodide hydrate structures are connected either via trigonal‐plane‐sharing or edge‐sharing, forming dimeric units. The antiprisms in calcium bromide enneahydrate are monomeric.     

Complexes and clusters of water relevant to atmospheric chemistry: H2O complexes with oxidants.

Experimental observations and data from quantum chemical calculations on complexes between water molecules and small, oxygen-containing inorganic species that play an important role as oxidants in the atmosphere (O(1D), O(3P), O2(X3sigmag), O2(b1sigmag+), O3, HO, HOO, HOOO, and H2O2) are reviewed, with emphasis on their structure, hydrogen bonding, interaction energies, thermodynamic parameters, and infrared spectra. In recent years, weakly bound complexes containing water have increasingly attracted scientific attention. Water in all its phases is a major player in the absorption of solar and terrestrial radiation. Thus, complexes between water and other atmospheric species may have a perceivable influence on the radiative balance and contribute to the greenhouse effect, even though their concentrations are low. In addition, they can play an important role in the chemistry of the Earth's atmosphere, particularly in the oxidation of trace gases. Apart from gas-phase complexes, the interactions of oxidants with ice surfaces have also received considerable advertency lately due to their importance in the chemistry of snow, ice clouds, and ice surfaces (e.g., ice shields in polar regions). In paleoclimate--respectively paleoenvironmental--studies, it is essential to understand the transfer processes from the atmosphere to the ice surface. Consequently, special attention is being paid here to the intercomparison of the properties of binary complexes and the complexes and clusters of more complicated compositions, including oxidants adsorbed on ice surfaces, where ice is considered a kind of large water cluster. Various facts concerning the chemistry of the Earth's atmosphere (concentration profiles and possible influence on radical reactions in the atmosphere) are discussed.     

Photocatalytic Oxidation of CO on TiO2: Chemisorption of O2, CO,and H2

On the surface : Adsorption of O₂ at the surface oxygen vacancy (SOV) sites of TiO₂ reconstructs the lattice oxygen (healing SOVs), resulting in a decrease of the photocatalytic activity of oxidizing CO over vacuum‐pretreated TiO₂ with increasing temperature (see scheme). Adsorption of H₂ produces new SOVs at the TiO₂ surface and stabilizes the photocatalytic activity.

     

Efficient thiocyanation of phenols and anilines in the CeBr3 / H2O2 system

An efficient electrophilic thiocyanation of phenols and anilines in the CeBr₃ / H₂O₂ system has been developed. The system CeBr₃ / H₂O₂ generates reactive brominating species which would react with NH₄SCN to deliver the active SCN cations in situ. The Br^- anion can be further oxidized to Br⁺, thereby furnishing the catalytic cycle.     

gamma-1,2-H2SiV2W10O40] immobilized on surface-modified SiO2 as a heterogeneous catalyst for liquid-phase oxidation with H2O2

An organic-inorganic hybrid support has been synthesized by covalently anchoring an N-octyldihydroimidazolium cation fragment onto SiO2 (denoted as 1-SiO2). This modified support was characterized by solid-state 13C, 29Si, and 31P NMR spectroscopy, IR spectroscopy, and elemental analysis. The results showed that the structure of the dihydroimidazolium skeleton is preserved on the surface of SiO2. The modified support can act as a good anion exchanger, which allows the catalytically active polyoxometalate anion [gamma-1,2-H2SiV2W10O40]4- (I) to be immobilized onto the support by a stoichiometric anion exchange (denoted as I/1-SiO2). The structure of anion I is preserved after the anion exchange, as confirmed by IR and 51V NMR spectroscopy. The catalytic performance for the oxidation of olefins and sulfides, with hydrogen peroxide (only one equivalent with respect to substrate) as the sole oxidant, was investigated with I/1-SiO2. This supported catalyst shows a high stereospecificity, diastereoselectivity, regioselectivity, and a high efficiency of hydrogen peroxide utilization for the oxidation of various olefins and sulfides without any loss of the intrinsic catalytic nature of the corresponding homogeneous analogue of I (i.e., the tetra-n-butylammonium salt of I, TBA-I), although the rates decreased to about half that with TBA-I. The oxidation can be stopped immediately by removal of the solid catalyst, and vanadium and tungsten species can hardly be found in the filtrate after removal of the catalyst. These results rule out any contribution to the observed catalysis from vanadium and tungsten species that leach into the reaction solution, which means that the observed catalysis is truly heterogeneous in nature. In addition, the catalyst is reusable for both epoxidation and sulfoxidation without any loss of catalytic performance.