Tropylium ion mediated α-cyanation of amines

Tropylium ion mediated α-cyanation of amines is described. Even in the presence of KCN, tropylium ion is capable of oxidizing various amine substrates, and the resulting iminium ions undergo salt metathesis with cyanide ion to produce aminonitriles. The byproducts of this transformation are simply cycloheptatriene, a volatile hydrocarbon, and water-soluble potassium tetrafluoroborate. Thirteen total substrates are shown for the α-cyanation procedure, including a gram scale synthesis of 17β-cyanosparteine. In addition, a tropylium ion mediated oxidative aza-Cope rearrangement is demonstrated.     

What determines MALDI ion yields? A molecular dynamics study of ion loss mechanisms

Ion recombination in matrix-assisted laser desorption/ionization (MALDI) is as important as any ion formation process in determining the quantity of ions observed but has received comparatively little attention. Molecular dynamics simulations are used here to investigate some models for recombination, including a Langevin-type model, a soft threshold model and a tunneling model. The latter was found to be superior due to its foundations in a widespread physical phenomenon, and its lack of excessive sensitivity to parameter choice. Tunneling recombination in the Marcus inverted region may be a major reason why MALDI is a viable analytical method, by allowing ion formation to exceed ion loss on the time scale of the plume expansion. Ion velocities, photoacoustic transients and pump-probe measurements might be used to investigate the role of recombination in different MALDI matrices, and to select new matrices.     

Thermal analysis of protein–metallic ion systems

Advanced thermal analysis methods, such as temperature modulated DSC (differential scanning calorimetry) and quasi-isothermal TMDSC were used to analyze the protein–metallic ion interactions in silk fibroin proteins. The precise heat capacities were measured and theoretically predicted in this study. To remove bound water and simplify the system, a thermal cycling treatment through both standard DSC and TMDSC was used to detect the underlying heat capacity and reveal the phase transitions of the silk–metallic salts system. Results show that K⁺ metallic salts play the role of plasticizer in silk fibroin proteins, which reduces the glass transition (T_g) of the pure silk protein and negatively affects its structural thermal stability. On the other hand, Ca²⁺ metallic salts act as an anti-plasticizer, and increase the glass transition and the thermal stability of the silk protein structure. This indicates that the thermal analysis methods offer a new pathway to study protein–metallic ion systems, yielding very fruitful information for the study of protein structures in the future.     

Salts of o,o′-diphenylenephenyloxonium ion

Summary o,o-Diphenylenephenyloxonium sulfate was prepared by us for the first time by heating an aqueous solution of o-phenoxy-o-biphenyldiazonium sulfate; a series of salts of this cation was prepared from this substance by double exchange reactions and the properties of these salts were studied.     

Determination of chloride ion by electrochemiluminescence and investigation of the mechanism

The electrochemiluminescence (ECL) of luminol in aqueous alkaline solution was studied.Trace amounts of chloride showed significant effect on the efficiency of light emission of luminol as a posi-tive trigonometrical wave pulse was exerted on the solution. The detection limit for the chloride is5.0 ×10~(-6) mol/L and the linear calibration range extends up to 1.0 ×10~(-2) mol/L; the relative standarddeviation for 1.0 ×10~(-5) mol / L chloride is 5%. The influencing factors for chloride determination arealso discussed. The possible mechanism for the electrochemiluminescence reaction may be due to theoxidation of chloride ion in the solution to ClO~-, and the latter acts on luminol and then gives outluminescence. The method has been applied to determine the total chloride in tap water with satisfactoryresults.     

Positive ion — negative ion coincidence spectroscopy of O2 and H2 using synchrotron radiation

Kinetic studies of the reactions of neutral lead clusters with NO₂, NO and O₂ were performed at 300 K. Reaction with NO₂ is rapid, with the observed second-order rate constants for most clusters being between 0.2 and 5 × 10^?11 cm³/s. There is a general trend of increasing rate with cluster size, although a few clusters display unusually high or low rates compared to ones of neighboring size. The reactions with NO are considerably slower by factors ranging from about 5 to 10. Reaction products are observed by laser ionization at 193 and 222 nm in conjunction with time-of-flight mass spectrometry. At lower fluence, the association products Pb _x (NO₂)⁺ and Pb _x (NO₂) ₂ ⁺ are observed in the case of reactions with NO₂. At higher laser fluence, Pb _x ⁺ and Pb _x O _x ^?1+ dominate the mass spectra of Pb _x reactions with NO₂, showing that the products fragment to more stable oxides. No reaction with oxygen was observed for any cluster, setting upper limits on the rates of 5 × 10^?14 cm³/s.     

Chemiluminescence flow Sensor for determination of the Ammonium ion

Anunoniaisasignificantalkalinepollutantintheatmosphere.AInInoniaeInittedintothetroposphereisreadilytraPpedbyacidicclouddropletSanditneutralizestheacidityofthedropletStoformammoniumsaltS.Therefore,thedetendnationoftheanunoniumioninwetdepositionisveryimportantinatmosphericchemistry,andthereisaneedforasimPleandrapidmethodforthedetendnationofNfu .Variousdetectionmethodsandtechniquesareusedfordetendninganunoniaorammoniumion,suchasionchromatography',ion-selectiveeIectrode',BLMselectrochendcalse…     

The thermodynamic stability of the LaBr 4 − ion

The thermodynamic stability of the LaBr ₄ ^? anion was for the first time studied by high-temperature mass spectrometry and nonempirical quantum-chemical methods. The experimental and theoretical enthalpies of the reaction $ LaBr_4^ - = Br^ - + LaBr_3 The thermodynamic stability of the LaBr₄⁻ anion was for the first time studied by high-temperature mass spectrometry and nonempirical quantum-chemical methods. The experimental and theoretical enthalpies of the reaction were Δ_r H°(298.15 K) = 302 ± 14 and 303 kJ/mol, respectively. The value Δ_f H° (LaBr₄⁻, g, 298.15 K) = −1105 ± 14 kJ/mol was recommended as the enthalpy of formation of the LaBr₄⁻ anion. Original Russian Text ? M.F. Butman, L.S. Kudin, V.B. Motalov, D.A. Ivanov, V.V. Sliznev, K.W. Kr?mer, 2008, published in Zhurnal Fizicheskoi Khimii, 2008, Vol. 82, No. 5, pp. 885–890.     

Enrichment of trace cerium subgroup rare earths by means of ion flotation

The possibility of ion flotation of cerium subgroup rare earths (Ce-subgroup) wasexplored. Various factors affecting the flotation efficiency were investigated. The results showedthat, by using sodium tetradecyl sulfate as the collector of trace Ce-subgroup and frother, over 95%of Ce-subgroup at ng/g levels could be separated from pH 2.3 media in 10--15 min. The proposedmethod has been applied to the determination of Ce-subgroup in a polluted farmland soil referencematerial (GBW 08303) with satisfactory results.     

Field asymmetric waveform ion mobility spectrometry studies of proteins: Dipole alignment in ion mobility spectrometry?

Approaches to separation and characterization of ions based on their mobilities in gases date back to the 1960s. Conventional ion mobility spectrometry (IMS) measures the absolute mobility, and field asymmetric waveform IMS (FAIMS) exploits the difference between mobilities at high and low electric fields. However, in all previous IMS and FAIMS experiments ions experienced an essentially free rotation; thus the separation was based on the orientationally averaged cross-sections Omega(avg) between ions and buffer gas molecules. Virtually all large ions are permanent electric dipoles that will be oriented by a sufficiently strong electric field. Under typical FAIMS conditions this will occur for dipole moments >400 D, found for many macroions including most proteins above approximately 30 kDa. Mobilities of aligned dipoles depend on directional cross-sections Omega(dir) (rather than Omega(avg)), which should have a major effect on FAIMS separation parameters. Here we report the FAIMS behavior of electrospray-ionization-generated ions for 10 proteins up to approximately 70 kDa. Those above 29 kDa exhibit a strong increase of mobility at high field, which is consistent with predicted ion dipole alignment. This effect expands the useful FAIMS separation power by an order of magnitude, allowing separation of up to approximately 10(2) distinct protein conformers and potentially revealing information about Omega(dir) and ion dipole moment that is of utility for structural characterization. Possible approaches to extending dipole alignment to smaller ions are discussed.     

Determination of debye temperatures of supported ion particles by m?ssbauer spectroscopy

The Debye temperatures of alumina- and titania-supported iron particles were determined using Mössbauer spectroscopy between 5 and 280 K. The Debye temperatures were obtained from a nonlinear optimization algorithm using the temperature dependence of the second order Doppler shift (SOD) and the resonant absorption area (RAA). To test its reliability, the same method was used to determine of an -iron-foil and pyrophoric iron.     

Plasmonics for the study of metal ion–protein interactions

The study of metal–protein interactions is an expanding field of research investigated by bioinorganic chemists as it has wide applications in biological systems. Very recently, it has been reported that it is possible to study metal–protein interactions by immobilizing biomolecules on metal surfaces and applying experimental approaches based on plasmonics which have usually been used to investigate protein–protein interactions. This is possible because the electronic structure of metals generates plasmons whose properties can be exploited to obtain information from biomolecules that interact not only with other molecules but also with ions in solution. One major challenge of such approaches is to immobilize the protein to be studied on a metal surface with preserved native structure. This review reports and discusses all the works that deal with such an expanding new field of application of plasmonics with specific attention to surface plasmon resonance, highlighting the advantages and drawbacks of such approaches in comparison with other experimental techniques traditionally used to study metal–protein interactions.

Microcalorimetric Study of the Action of Yb^3＋ ion on the Growth of Staphylococcus aureus

A microcalorimetric method was used to evaluate the action of Yb^3 ions onthe growth metabolism of Staphylococcus aureus.The power-time curves of the growth metabolism of Staphylo.coccus aureus and the action of Yb^3 ions were obtained by us-ing stopped-flow method at 37 ℃. For evaluation of the action,the growth rate constants ( k1 and k2) for the log phase 1, log phase 2, and the total heat effect (Qtotal) for Staphylococcus aureus were determined. The results show that Yb^3 ions at low concentrations have the stimnlatory effect on Staphylococcus au-reus and that Yb^3 ions at higher concentration could inhibit its growth.     

Gas phase ion molecule chemistry of tetracarbonyl (η5-cyclopentadienyl) vanadium by Fourier transform ion cyclotron resonance

The kinetics of the reactions between the CpV(CO)₄ molecule and its fragment cations and anions have been examined using Fourier transform ion cyclotron resonance (FTICR) techniques. With 25 eV electron impact ionization the fragment cations V⁺ and CpV(CO)_n=0–4⁺ react principally by charge exchange or by condensation with the parent neutral molecule. Rate constants for these pathways have been determined along with kinetic evidence for the existence of excited state cations. Some of the product cations show unexpected stability despite their large formal electron deficiency. Exchange of carbonyl ligands was also observed. Under 2.5 eV electron impact, only two anions are produced: CpV(CO)_n=2,3⁻, both of which are unreactive with the parent neutral.     

Air–water interfacial behavior of amphiphilic peptide analogs of synthetic chloride ion transporters

A family of heptapeptide-based chloride transporters (called synthetic anion transporters, SATs) were designed to insert into phospholipid membrane bilayers and form pores. Many of these compounds have proved to be chloride selective transporters. The transporters were designed to incorporate hydrophilic heptapeptides that could serves as headgroups and hydrocarbon tails that could serve as hydrophobic membrane anchors. Insertion of the SAT molecules into a bilayer requires approach to and insertion at the aqueous-membrane surface. The studies reported here were conducted to model and understand this process by studying SAT behavior at the air–water interface. A Langmuir trough was used to obtain surface pressure–area isotherm data. These data for amphiphilic SATs were augmented by Brewster angle microscopy (BAM), molecular modeling, and calculations of the hydrophobicity parameter log P. The analyses showed that the heptapeptide (hydrophilic) module of the SAT molecule rested on the water surface while the dialkyl (hydrophobic) tails oriented themselves in the air, perpendicular to the water surface. Brewster angle microscopy visually confirmed a high order of molecular organization. Results from these studies are consistent with the previously proposed mechanism of SAT membrane insertion and pore formation.     

Transfer of lanthanum ion across the adsorption of emulsifier OP at the water-nitrobenzene interface

The transfer of lanthanum ion facilitated by diantipyrylmathane (DAM) across the water/nitrobenzene (w/nb) interface and the adsorption of emulsifier OP at the w/nb interface has been studied by the cyclic voltammetry.The mechanism of the charge transfer reactions is discussed.It has been concluded that the transfer of rare earth metal ion (La3+) facilitated by neutral ionophore (DAM) at the w/nb interface is E mechanism and the nonionic surfactant (emulsifier OP) can participate in the charge transfer process as an ionophore,charge transfer catalyst and inhibitor.     

Studies on the Copolymerization of Propylene and Butadiene with Supported Titanium Catalysts (I)——Copolymerizat ion and Characterizat ion of the Products

Copolymerizations of propylene and butadiene in various ratios with two kinds of supported catalysts, i.e. TiCl4/MgCl2/AlEt3 and TiCl4/MgCl2/AlEt3/ethyl Bonzoate(EB). have been investigated. The results show that these two catalysts are quite effective for propylene-butadiene copolymerization but behave in different features. Characterizations of the copolymerization products by solvent extraction, IR, 13C NMR, X-ray diffraction and DTA show that blocked propylene-propylene and butadiene-butadiene sequences exist in polymer chain and the butadiene units are exclusively in trans-1,4 configuration.     

Review of vanadium-based electrode materials for rechargeable aqueous zinc ion batteries

In recent years,rechargeable aqueous zinc ion batteries(ZIBs),as emerging energy storage devices,stand out from numerous metal ion batteries.Due to the advantages of low cost,environmentally friendly characteristic and safety,ZIBs can be considered as alternatives to lithium-ion batteries(LIBs).Vanadiumbased compounds with various structures and large layer spacings are considered as suitable cathode candidates for ZIBs.In this review,the recent research advances of vanadium-based electrode materials are systematically summarized.The electrode design strategy,electrochemical performances and energy storage mechanisms are emphasized.Finally,we point out the limitation of vanadium-based materials at present and the future prospect.     

Photoluminescence investigation of MPA–ZnS QDs interaction with selenite ion

The interaction between water-soluble zinc sulfide quantum dots (ZnS QDs) and selenite ion was investigated by photoluminescence method. The water-soluble ZnS QDs were synthesized using a simple and fast procedure based on the co-precipitation of nanoparticles in an aqueous solution in the presence of 3-mercaptopropionic acid (MPA), as the capping agent. Fluorescence intensity for MPA–ZnS QDs, with a strong fluorescent emission at about 430 nm, decreased in the presence of selenite. The influence of the effective parameters including pH and temperature was investigated. The results showed that under the optimum conditions, the fluorescence intensity change of QDs was linearly proportional to the selenite concentration in the range 4.0 × 10^?5–7.2 × 10^?4 mol L^?1. Moreover, the quenching mechanism was discussed to be a static quenching procedure.