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.     

Gallium-based anodes for alkali metal ion batteries

Alkali metal ion batteries(AMIBs)are playing an irreplaceable part in the energy revolution,due to their intrinsic advantages of large capacity/power density and abundance of alkali metal ions in the earth’s crust.Despite their great promise,the inborn deficiencies of commercial graphite and other anodes being researched so far call for the quest of better alternatives that exhibit all-round performance with the balance of energy/power density and cycling stability.Gallium-based materials,with impressive capacity utilization and self-healing ability,provide an anticipated solution to this conundrum.In this review,an overview on the recent progress of gallium-based anodes and their storage mechanism is presented.The current strategies used as engineering solutions to meet the scientific challenges ahead are discussed,in addition to the insightful outlook for possible future study.     

Negative ion photoelectron spectroscopy of teo−

We have recorded the photoelectron spectrum of Te0⁻ using a hot-cathode discharge ion source and a negative ion photoelectron spectrometer. The adiabatic electron affinity of TeO is determined to be 1.697±0.022 eV. The negative ion parameters determined in this work are: (w_e″(TeO⁻) = 690 ± 80 cm⁻¹, r_e″(TeO⁻) = 1.884 ± 0.028 Å. and D_o     

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.     

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.     

Reactions involving fluoride ion. Part 37. ‘Proton Sponge’ hydrofluoride as a fluoride ion donor

‘Proton Sponge’ hydrofluoride has been prepared and is totally soluble in acetonitrile; this system has been used to generate carbanions from hexafluoropropene and to form carbon-fluorine bonds by reaction with both 2,4,6-trichloropyrimidine and benzoyl chloride.     

Effect of the porosity of PS–DVB-copolymers on ion chromatographic behavior in inverse size-exclusion and ion chromatography

Small and highly pressure-stable PS-DVB copolymers of different porosity had been prepared by a two-step swelling procedure which enabled variation of diluent composition, an important characteristic affecting the porosity. The polymers were characterized by inverse size-exclusion chromatography and scanning electron microscopy. Subsequent chloromethylation and amination resulted in anion exchangers suitable for ion chromatography.The pore volume and the pore-size distribution is substantially affected by the fraction of the solvens component in the diluent. It was apparent from scanning electron microscopy that surface structure and the size of the polymer particles was not affected by diluent composition. The functionalization process led to a decrease in pore volume. The pore-size distribution remained unchanged during functionalization, which can be explained in terms of partial closing of all pore sizes. The chromatographic efficiency of the functionalized polymers in ion chromatography was highly dependent on diluent composition and the extent of functionalization was determined by the total pore volume.The composition of the diluent is an excellent tool for optimization of polymers used for the synthesis of surface-functionalized anion exchangers.     

Study of ion transport across an amphoteric ion exchange membrane — general transport properties of a simple electrolyte

Basic electrochemical properties of an amphoteric ion-exchange membrane (1.0—PA—29), in which almost equal numbers of cationic and anionic sites are distributed homogeneously over the functionalized polymer networks, were studied for a variety of concentration-cell systems. Unlike the usual uniform ion-exchange membrane, potentiometric permselectivities were demonstrated even for ions of the same charge, as shown by the result that distinctive potential responses were observed for a series of alkali metal chloride, sodium salt, and tetra-alkylammonium chloride systems. The sequence of membrane permeabilities to cations and anions calculated from the electrochemical data could well be correlated to the sequence of the hydrated radii of the respective ions. So the potentiometric responses to any electrolyte system can be predicted from the permeability data or hydrated radius values of individual cations and anions. The present results suggest that the homogeneous amphoteric ion-exchange membrane functions effectively as an ion sieve, sifting out the sizes of permeating hydrated cations and anions.     

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.     

IMAC—Immobilized metal ion affinity based chromatography

Immobilized metal ion affinity chromatography (IMAC) is a highly versatile separation method based on interfacial interactions between biopolymers in solution and metal ions fixed to a solid support, which is usually a hydrophilic cross-linked polymer.Polymer-fixed Zn(II), Ni(II), Co(II) and Cu(II) are particularly well suited for fractionation of proteins primarily on the basis of their relative content of surface-located imidazole residues but also of Trp and Cys residues as well as terminal amino groups.IMA methods can also be devised for purification of phosphoproteins and calcium-binding proteins. In some instances, the performance of IMA gels is comparable to that of biospecific affinity-based adsorbents. In fact IMA gels may, by sandwich techniques, occasionally be converted to biospecific adsorbents.Selectivity can be varied by choice of type of ligand and metal ion as well as by varying the modes of elution, including affinity desorption.     

What ion is generated when ionizing acetonitrile?

It has long been assumed that ionizing neutral acetonitrile produces ions with the same atomic connectivity, CH(3)CN(+*). Recent calculations on the C(2)H(3)N(+*) potential energy surface have suggested that it may be difficult to generate pure CH(3)CN(+*) when ionizing acetonitrile. We have probed the interconversion of CH(3)CN(+*) and its lower energy isomer CH(2)CNH(+*) by calculation, collision-induced dissociation mass spectrometry and ion-molecule reaction. The latter ion, ionized ketenimine, is co-generated upon electron or chemical ionization of neutral acetonitrile in the ion source of a mass spectrometer. An estimate of the ratio of the two isomers can be obtained from their respective ion-molecule reactions with CO(2) or COS. CH(3)CN(+*) reacts by proton-transfer with CO(2) and charge transfer with COS, whereas CH(2)CNH(+*) is unreactive.     

Developments in ion mobility spectrometry–mass spectrometry

Ion mobility spectrometry (IMS) has been used for over 30 years as a sensitive detector of organic compounds. The following is a brief review of IMS and its principles with an emphasis on its usage when coupled to mass spectrometry. Since its inception, IMS has been interfaced with quadrupole, time-of-flight, and Fourier-transform ion cyclotron resonance mass spectrometry. These hybrid instruments have been employed for the analysis of a variety of target analytes, including biomolecules, explosives, chemical warfare degradation products, and illicit drugs.     

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.     

Fluoride ion sensing by an anion-π interaction

We report the discovery of a supramolecular interaction (anion-π and charge/electron transfer, CT/ET) involving fluoride ion and π-electron deficient colorless naphthalene diimide (NDI) receptors. Strong electronic interactions between lone-pair electrons of F(-) ion and π*-orbitals of the NDI unit lead to an unprecedented F(-)→NDI ET event, which produces an orange colored NDI(?-) radical anion. Further reduction of NDI(?-) by another F(-) ion produces a pink colored NDI(2-) dianion, rendering NDI a colorimetric F(-) sensor. Preorganization of two NDI units in overlapping positions using folded linkers improves their selectivity and sensitivity for the F(-) ion significantly, allowing F(-) detection at nM concentration in 85:15 DMSO/H(2)O solutions.     

Hydroxide and hydronium ion adsorption — A survey

The propensity of hydroxide and hydronium ions to accumulate at interfaces is the subject of ongoing scientific debate. Electrokinetic and surface force measurements suggest elevated interfacial concentrations of hydroxide ions across a wide range of pHs. Contrary to this, however, surface-sensitive spectroscopic techniques and molecular dynamic (MD) simulations indicate that hydronium ions have strong surface affinity under similar conditions. Here we review results obtained for gas/water, oil/water and solid/water interfaces. Emphasis is placed on ion adsorption phenomena occurring on polymer films of different hydrophobicity and structure. The results clearly show that asymmetric water ion adsorption is independent of the hydrophobicity of the solid surface. Recently obtained data reveal significant effects of the hydroxide and hydronium ions even on the charging of hydrophobic polymers in the presence of multivalent electrolytes and on the charging of zwitterionic lipid membranes.     

Reactions of O−. with methyl benzoate: A negative ion chemical ionization and Fourier transform ion cyclotron resonance study

The reactions of O*- with methyl benzoate have been examined by the measurement of negative ion chemical ionization (NICI) mass spectra using a CI source, with confirmatory studies carried out on a Fourier transform ion cyclotron resonance mass spectrometer. Reaction mechanisms have been elucidated using isotopically labeled esters. Nucleophilic attack at the carbonyl carbon and the aromatic ring were important reaction pathways. Nucleophilic attack at the carbonyl carbon was followed by the production of products (C6HsCO2- and CH3OCO2-) characteristic of radical, beta-fragmentation. Using 18O-labeled methyl benzoate, the SN2 reaction was found to account for a smaller percentage, 21(+/-1)%, of the benzoate product. Aromatic ring attack resulted in formation of [M + O - H]- and [M - 2H]*- ions. Although aryl hydrogens accounted for most H2*+ abstracted by O*-, evidence for abstraction of HarylH*+alkyl and HalkylH*+alkyl was also found. Although present at much lower abundance, dehydrobenzoate, dehydrophenoxy, and C7H6*- ([M - 2H - CO2]*-) radical anions were also observed. An Haryl/Halkyl exchange associated with formation of the benzoate anion was attributed to an Halkyl abstraction that occurred within the methanol/dehydrobenzoate ion-dipole complex. The [M - 2H]*-, dehydrobenzoate, dehydrophenoxy, and [M - 2H - CO2]*- ion signals were quenched by reaction with O2. Conditions required for production of O*- spectra under NICI conditions were also examined.     

Chemiluminescence flow Sensor for determination of the Ammonium ion

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