Hydrogen Sulfate Anion Research Articles

A facile and efficient synthesis of tri- and tetrasubstituted imidazoles with potassium hydrogen sulfate and DB18C6 in an aqueous medium

Potassium hydrogen sulfate in the presence of dibenzo-18-crown-6 (DB18C6) turns out to be a very efficient and effective catalyst for the facile synthesis of a wide variety of tri- and tetrasubstituted imidazoles in an aqueous medium at moderate temperature. The idea behind this is that the potassium ion, being trapped in the crown core, frees the hydrogen sulfate anion, which, because of its acidic nature, succeeds in the ready synthesis of the imidazoles.

Tris(cis-2-hydroxycyclohexane-1,3,5-triaminium) hydrogen sulfate octachloride dihydrate

The 2-hy­droxy­cyclo­hexane-1,3,5-triaminium (= H3 L 3+) cation of the title compound, 3C6H18N3O3+·8Cl−·HSO4 −·2H2O, exhibits a cyclo­hexane chair with three equatorial ammonium groups and one axial hy­droxy group in an all-cis configuration. The hydrogen sulfate anion and two water mol­ecules lie on or in proximity to a threefold axis and are disordered. The crystal structure features N—H⋯Cl and O—H⋯Cl hydrogen bonds. Three C 3-symmetric motifs can be identified in the structure: (i) Two chloride ions (on the C 3-axis) together with three H3 L 3+ cations constitute an [(H3 L)3Cl2]7+ cage. (ii) The lipophilic C6H6-sides of three H3 L 3+ cations, which are oriented directly towards the C 3-axis, generate a lipophilic void. The void is filled with the disordered water mol­ecules and with the disordered part of the hydrogen sulfate ion. The hydrogen atoms of these disordered moieties were not located. (iii) Three H3 L 3+ cations together with one HSO4 − and three Cl− counter-ions form an [(HSO4)(H3 L)3Cl3]5+ cage. Looking along the C 3-axis, these three motifs are arranged in the order (cage 1)⋯(lipophilic void)⋯(cage 2). The crystal studied was found to be a racemic twin.

Lawsone (2-hydroxy-1,4-naphthoquinone) as a sensitive cyanide and acetate sensor

Lawsone (2-hydroxy-1,4-naphthoquinone), the essential component of henna, is used as a sensitive colorimetric and electrochemical sensor for anions such as cyanide, acetate, fluoride and dihydrogen phosphate (DHP) in acetonitrile. These anions cause a color change in Lawsone's solution from yellow to orange-red. Other anions, such as chloride, bromide, iodide, perchlorate, do not show a significant change. Cyanide changes the color of Lawsone in water:acetonitrile (95:5) solution significantly while acetate causes a slight color change. On the other hand, hydrogen sulfate anion fades the yellow color of the solution. Job's plots show a 1:1 host:guest complex in acetonitrile for cyanide, acetate and fluorides and 1:2 for DHP. In water/acetonitrile the stoichiometry is 1:1 for host:anion. The binding constants show strong binding with cyanide and acetate in both solvent systems.

Synthesis and Electrochemical Anion-Sensing Properties of a Biferrocenyl-Functionalized Dendrimer

The synthesis and electrochemical anion-sensing properties of a diaminobutane poly(propyleneimine) dendrimer functionalized with biferrocenyl units 2 are presented. The redox activity of the ferrocenyl centers in 2 has been characterized by cyclic voltammetry. Cyclic and square wave voltammetric investigations demonstrate that tetraferrocenyl compound 2 and the reference compound 1 show electrochemical anion-sensing action: they display a cathodic shift of the ferrocene–ferrocenium redox couple with dihydrogenphosphate and hydrogensulfate anions in solution and immobilized onto electrode surfaces.

Turn-on of the fluorescence of tetra(4-pyridylphenyl)ethylene by the synergistic interactions of mercury(ii) cation and hydrogen sulfate anion

The fluorescence of tetra(4-pyridylphenyl)ethylene (1) can be switched on significantly by the synergistic interactions of Hg(2+) and HSO(4)(-) based on a new aggregation mechanism for tetraphenylethylene molecules.

Counter-ion effect on surfactant–DNA gel particles as controlled DNA delivery systems

The ability to entrap drugs within vehicles and subsequently release them has led to new treatments for a number of diseases. Based on an associative phase separation and interfacial diffusion approach, we developed a way to prepare DNA gel particles without adding any kind of cross-linker or organic solvent. Among the various agents studied, cationic surfactants offered particularly efficient control for encapsulation and DNA release from these DNA gel particles. The driving force for this strong association is the electrostatic interaction between the two components, as induced by the entropic increase due to the release of the respective counter-ions. However, little is known about the influence of the respective counter-ions on this surfactant–DNA interaction. Here we examined the effect of different counter-ions on the formation and properties of the DNA gel particles by mixing DNA (either single- (ssDNA) or double-stranded (dsDNA)) with the single chain surfactant dodecyltrimethylammonium (DTA). In particular, we used as counter-ions of this surfactant the hydrogen sulfate and trifluoromethane sulfonate anions and the two halides, chloride and bromide. Effects on the morphology of the particles obtained, the encapsulation of DNA and its release, as well as the haemocompatibility of these particles are presented, using counter-ion structure and DNA conformation as controlling parameters. Analysis of the data indicates that the degree of counter-ion dissociation from the surfactant micelles and the polar/hydrophobic character of the counter-ion are important parameters in the final properties of the particles. The stronger interaction with amphiphiles for ssDNA than for dsDNA suggests the important role of hydrophobic interactions in DNA.

Synthesis and evaluation of thiosemicarbazones functionalized with furyl moieties as new chemosensors for anion recognition

A family of heterocyclic thiosemicarbazone dyes (3a-f and 4) containing furyl groups was synthesized in good yields, characterized and their response in acetonitrile in the presence of selected anions was studied. Acetonitrile solutions of 3a-f and 4 showed absorption bands in the 335-396 nm range which are modulated by the electron donor or acceptor strength of the heterocyclic systems appended to the thiosemicarbazone moiety. Fluoride, chloride, bromide, iodide, dihydrogen phosphate, hydrogen sulphate, nitrate, acetate and cyanide anions were used in recognition studies. From these anions, only sensing features were seen for fluoride, cyanide, acetate and dihydrogen phosphate. Two clearly different chromo-fluorogenic behaviours were observed: (i) a small shift of the absorption band due to the coordination of the anions with the thiourea protons and (ii) the appearance of a new red shifted band due to deprotonation. For the latter effect, a change in the colour of solution from pale yellow to purple was observed. Fluorescence studies were also in agreement with the different effects observed in the UV/Vis titrations. In this case, hydrogen bonding interactions were visible through the enhancement of the emission band, whereas deprotonation induced the appearance of a new red-shifted emission. Logarithms of stability constants for the two processes (complex formation + deprotonation) for receptors in the presence of fluoride and acetate anions were determined from spectrophotometric titrations using the HypSpec V1.1.18 program. Semi-empirical calculations to evaluate the hydrogen-donating ability of the receptors and a prospective electrochemical characterization of compound in the presence of fluoride were also performed.

A BODIPY derivative as a highly selective “Off–On” fluorescent chemosensor for hydrogen sulfate anion

A new fluorescent receptor for 1 anions has been synthesized by the combination of BODIPY dye and indole moiety. The binding and sensing abilities of receptor 1 toward various anions have been studied by absorption, emission and (1)H NMR titrations spectroscopies. Receptor 1 could act as a highly selective "Off-On" fluorescent sensor for hydrogen sulfate anion in CH(3)CN solvent and CH(3)CN-H(2)O medium. The fluorescence response of receptor 1 toward HSO(4)(-) in CH(3)CN solvent could be due to the suppressed PET (photo-induced electron transfer) process induced by the multiple hydrogen bonding interactions between receptor 1 and HSO(4)(-). In CH(3)CN-H(2)O medium, the HSO(4)(-)-induced change is mainly the consequence of a simple protonation of the CH=N- moiety of receptor 1, which inhibited the PET process and "turned on" the fluorescence of 1.

Protic Ionic Liquids Based on Decahydroisoquinoline: Lost Superfragility and Ionicity-Fragility Correlation

Physicochemical properties, ionicity, and fragility for protic ionic liquids (PILs) based on the protonation of the extremely fragile molecular liquid decahydroisoquinoline (DHiQ) by various Brønsted acids have been studied. The ionicity was evaluated using the Walden plot diagnostic, while the m-fragility (slope of T(g)-scaled Arrhenius plot at T(g)) was quantitatively measured by the Moynihan-Wang-Velikov variable scan rate, differential scanning calorimetry, method. DHiQ-derived PILs prove to cover the whole range of IL ionicities from poor IL to good IL, and even superionic, assessed from the Walden plot, depending on the choice of Brønsted acid. We find that the superfragile character of the parent DHiQ becomes completely suppressed upon conversion to ionic liquid, the initial value m = 128 sinking to m = 45-91 for the ionic liquid. Such values are in the intermediate to fragile range. The DHiQ-based PIL showing superionic behavior, anion [HSO(4)(-)], proves to be the case with the lowest m value (m = 45) so far reported for either aprotic or protic ILs. Both low fragility and dry proton conductivity can be attributed to an extended hydrogen bond network that is set up by the hydrogensulfate anion. The good DHiQ PILs have m values similar to those reported for typical aprotic ILs (m = 60-80), while the poor DHiQ PILs in which proton transfer from acid to base is weak show some memory of the parent fragility. Thus, a correlation of ionicity with m-fragility is characteristic of this system. A range of noncrystallizing, and also nonglassforming, behavior is observed in this series of compounds, suggesting a possible test for ideal glassformer existence.

Cossaite, (Mg0.5,☐)Al6(SO4)6(HSO4)F6·36H2O, a new mineral from La Fossa crater, Vulcano, Aeolian Islands, Italy

AbstractCossaite, ideally (Mg0.5,☐)Al6(SO4)6(HSO4)F6·36H20, was found in the altered pyroclastic breccia of an active fumarole (T about 350°C) located at the rim of the La Fossa crater, Vulcano Island, Aeolian archipelago, Sicily, Italy. Cossaite is trigonal, space group R3̄, with a = 22.010(2), c = 9.238(1) Å, V = 3875.6(6) Å3, Z = 3. It forms stout prismatic hexagonal crystals up to 100 μm in size, terminated by rhombohedral faces, and is associated with thermessaite, vlodavetsite, sassolite and salammoniac. Cossaite is colourless to white, the streak is white and the lustre vitreous. It is not fluorescent in either long-wave or short-wave ultraviolet radiation. The calculated density is 2.075 g cm–3. The mean refractive index nobs is 1.49(1) (589 nm). Chemical analysis gave MgO 1.4, A12O3 19.5, SO3 34.7, F 5.7, (H2O 40.85, from structure refinement), O=F –2.4, total 99.75 wt.%, corresponding to the empirical formula Mg0.56Al6.19S7.01H73.37F4.85O65.15 calculated on the basis of 70 oxygen plus fluorine atoms. The strongest six lines in the X-ray powder diffraction pattern [dobs(Å) (I) (hkl)] are: 4.15 (100) (140), 3.87 (70) (32̄2), 11.00 (50) (110), 4.58 (25) (131), 2.770 (20) (3̄33), 2.166 (20) (1̄8̄1). The crystal structure was refined to a final R index of 0.0349. It contains octahedral [A1(H2O)5F]2+ cations and sulphate anions interacting via hydrogen bonds to form channels running along [001], where disordered [Mg(H2O)6]2+ cations and hydrogensulphate anions are hosted.

Water-induced pseudo-quadruple hydrogen-bonding motifs in xanthine–inorganic acid complexes

In xanthinium nitrate hydrate [systematic name: 2,6-dioxo-1,2,3,6-tetrahydro-9H-purin-7-ium nitrate monohydrate], C(5)H(5)N(4)O(2)(+)·NO(3)(-)·H(2)O, (I), and xanthinium hydrogen sulfate hydrate [systematic name: 2,6-dioxo-1,2,3,6-tetrahydro-9H-purin-7-ium hydrogen sulfate monohydrate], C(5)H(5)N(4)O(2)(+)·HSO(4)(-)·H(2)O, (II), the xanthine molecules are protonated at the imine N atom with the transfer of an H atom from the inorganic acid. The asymmetric unit of (I) contains a xanthinium cation, a nitrate anion and one water molecule, while that of (II) contains two crystallographically independent xanthinium cations, two hydrogen sulfate anions and two water molecules. A pseudo-quadruple hydrogen-bonding motif is formed between the xanthinium cations and the water molecules via N-H···O and O-H···O hydrogen bonds in both structures, and leads to the formation of one-dimensional polymeric tapes. These cation-water tapes are further connected by the respective anions and aggregate into two-dimensional hydrogen-bonded sheets in (I) and three-dimensional arrangements in (II).

Thermophysical properties of room temperature ionic liquids with oligomeric formate and hydrogen sulfate

Brønsted acid room temperature ionic liquids (RTILs) comprised of oligomeric formate (or hydrogen sulfate) anions and pyrrolidinium-based cations are prepared. It is found that ion identity greatly affects the thermophysical properties. All RTILs studied here are liquid and have a high ionic conductivity (up to 55.4 mS/cm) and a low viscosity (down to 6.42 mPa s) at room temperature. The incorporation of oligomeric anions in ILs significantly increases the density and conductivity, and decreases the viscosity. The correlation between ionic conductivity and viscosity is based on the classical Walden rule; a relatively large deviation of the plots from the ideal Walden line is observed for formate-based ILs synthesized using equimolar amounts of acid and base, whereas the deviation decreases significantly when the formate-based ILs contain oligomeric anions. The Stokes–Einstein plot of DT −1 vs. η −1 for ferrocence in ILs shows that hydrodynamic radius of diffusing species is independent of temperature.

Temperature Dependence Measurements and Structural Characterization of Trimethyl Ammonium Ionic Liquids with a Highly Polar Solvent

We report the synthesis and characterization of a series of an ammonium ionic liquids (ILs) containing acetate, dihydrogen phosphate, and hydrogen sulfate anions with a common cation. To characterize the thermophysical properties of these newly synthesized ILs with the highly polar solvent N,N-dimethylformamide (DMF), precise measurements such as densities (ρ) and ultrasonic sound velocities (u) over the whole composition range have been performed at atmospheric pressure and over wide temperature ranges (25-50 °C). The excess molar volume (V(E)) and the deviation in isentropic compressibilities (Δκ(s)) were predicted using these temperature dependence properties as a function of the concentration of ILs. The Redlich-Kister polynomial was used to correlate the results. The ILs investigated in the present study included trimethylammonium acetate [(CH(3))(3)NH][CH(3)COO] (TMAA), trimethylammonium dihydrogen phosphate [(CH(3))(3)NH][H(2)PO(4)] (TMAP), and trimethylammonium hydrogen sulfate [(CH(3))(3)NH][HSO(4)] (TMAS). The intermolecular interactions and structural effects were analyzed on the basis of the measured and the derived properties. In addition, the hydrogen bonding between ILs and DMF has been demonstrated using semiempirical calculations with help of Hyperchem 7. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding between ILs and DMF molecules and their structural factors. The influence of the anion of the protic IL, namely, acetate (CH(3)COO), dihydrogen phosphate (H(2)PO(4)), and hydrogen sulfate (HSO(4)), on the thermophysical properties is also provided.

2-(3-Pyridyl)imidazole-4,5-dicarboxylic acid based lanthanide luminescent anion sensor

A novel terbium 2-(3-pyridyl)imidazole-4,5-dicarboxylic acid complex was incorporated into inorganic host (tetrethoxysilane, TEOS) and we developed a green luminescent hybrid material via a sol–gel reaction. The sensing abilities of this material were studied by addition of HSO 4 − , F −, Cl −, Br −, I − and CH 3COO − to aqueous suspension of the assayed bulk material. The titration of hydrogen sulfate (detection limit 10 −5 M) resulted in the reduction of the green luminescence, whereas fluoride ions (detection limit 10 −4 M) caused the luminescence changing from green to blue. We recognized that fluoride ion forms hydrogen bonding interactions with ligand. But hydrogen sulfate anion changed the green emission mainly because of its acidity.

2-Aminopyrimidinium hydrogen sulfate

In the crystal structure of the title compound, C4H6N3 +·HSO4 −, hydrogen sulfate anions self-assemble through O—H⋯O hydrogen bonds, forming chains along the b axis, while the cations form centrosymmetric pairs via N—H⋯N hydrogen bonds. The 2-amino­pyrimidinium pairs are linked to the sulfate anions via N—H⋯O hydrogen bonds, forming a two-dimensional network parallel to (10). In addition, weak inter­molecular C—H⋯O contacts generate a three-dimensional network.

Ferrocenyl Functionalized Silver-Chalcogenide Nanoclusters

New (chalcogenoethyl)ferrocenylcarboxalate functionalized silver chalcogenide nanoclusters were synthesized using a combination of silylated chalcogen reagents at low temperatures. The addition of E(SiMe(3))(2) to reaction mixtures of FcC{O}OCH(2)CH(2)ESiMe(3) (E = S, Se) and (Ph(3)P)(2)·AgOAc affords nanoclusters with approximate molecular formulas [Ag(36)S(9)(SCH(2)CH(2)O{O}CFc)(18)(PPh(3))(3)] (1), [Ag(100)Se(17)(SeCH(2)CH(2)O{O}CFc)(66)(PPh(3))(10)] (2), and [Ag(180)Se(54)(SeCH(2)CH(2)O{O}CFc)(72)(PPh(3))(14)] (3) as noncrystalline solids. Compositions were formulated on the basis of elemental analysis, high resolution transmission electron microscopy, and dynamic light scattering experiments. Solutions of these polyferrocenyl assemblies display a single quasi-reversible redox wave with some adsorption to the electrode surface as studied by cyclic voltammetry. With the smaller clusters 1, the addition of [Bu(4)N][HSO(4)] results in a shift of the reduction wave to less positive potentials than those of the complex in the absence of these oxoanions. No further shift is observed after the addition of approximately 1 equivalent of HSO(4)(-)/ferrocene branch. Cyclic voltammograms of the larger clusters 2 and 3 show the appearance of a new, irreversible wave at less positive potentials than the initial wave upon the addition of HSO(4)(-). The appearance of this new wave together with the disappearance of the reduction wave indicates a stronger interaction between the nanoclusters and the hydrogen sulfate anion.

Anion‐binding properties of two calix[4]arene derivatives containing two ferrocene imine or ferrocene amine units at the upper rim

AbstractCalix[4]arene derivatives containing ferrocene units at the upper rim have been synthesized and their anion‐binding and sensing investigated towards anions such as chloride, bromide and hydrogen sulfate by cyclic voltammetry. Electrochemical studies show that these redox‐active ligands electrochemically recognize chloride and bromide anions. These compounds have excellent selectivity for chloride and bromide ions, in the comparison with hydrogen sulfate anion. With ferrocenyl Schiff base calix[4]arene 1 an anodic shift as large as 302 mV is observed on addition of four equivalents of Cl− anion. Also electrochemical and UV–vis spectroscopic titrations ferrocenyl calix[4]arene derivatives 1 with chloride and bromide ions and 2 (only with Cl−) indicate a 1:1 binding‐stiochiometry. Copyright © 2011 John Wiley & Sons, Ltd.

Influence of Brønsted acid ionic liquid structure on hydroxyacid polyesterification

Bronsted acid ionic liquids (BAILs) based on the 4-(3′-butyl-1′-imidazolio)-1-butanesulfonic acid cation were found to be very efficient polyesterification solvents and catalysts. Only 5–30 min at 90–110 °C was required to obtain high molar mass poly(12-hydroxydodecanoic acid) (Mw up to 40000 g mol−1). The polyesterification was faster in BAILs with the bis(trifluoromethylsulfonyl)imidide anion (Tf2N), but small amounts of ethers and double bonds arising from side reactions were detected in the final polymer. On the other hand, no side reactions took place in the BAIL with the hydrogen sulfate anion, except for the formation of a sulfonate ester intermediate that can further react with carboxylic acid groups to yield the expected ester. This intermediate, not observed in Tf2N-based BAILs, might be involved in the protection of hydroxy end groups from etherification side reactions in HSO4−-based BAILs. To explain the different behaviors of these BAILs, and since the acidity of H2SO4 is much higher than that of Tf2NH, it is suggested that the structure of these BAILs could be different: alkylsulfonic acid-substituted imidazolium for the former, while the latter could be just a mixture of imidazolium–sulfonate zwitterion and Tf2NH. The influence of reaction temperature, water elimination method and BAIL concentration on polyesterification are also discussed.

Ionic liquid pretreatment of lignocellulosic biomass with ionic liquid–water mixtures

Ground lignocellulosic biomass (Miscanthus giganteus, pine (Pinus sylvestris) and willow (Salix viminalis)) was pretreated with ionic liquid–water mixtures of 1-butyl-3-methylimidazolium methyl sulfate and 1-butyl-3-methylimidazolium hydrogen sulfate. A solid fraction enriched in cellulose was recovered, which was subjected to enzymatic hydrolysis. Up to 90% of the glucose and 25% of the hemicellulose contained in the original biomass were released by the combined ionic liquid pretreatment and the enzymatic hydrolysis. After the pretreatment, the ionic liquid liquor contained the majority of the lignin and the hemicellulose. The lignin portion was partially precipitated from the liquor upon dilution with water. The amount of hemicellulose monomers in the ionic liquid liquor and their conversion into furfurals was also examined. The performance of ionic liquid–water mixtures containing 1,3-dialkylimidazolium ionic liquids with acetate, methanesulfonate, trifluoromethanesulfonate and chloride anions was investigated. The applicability of the ionic liquid 1-butylimidazolium hydrogensulfate for lignocellulose pretreatment was also examined. It was found that ionic liquid liquors containing methyl sulfate, hydrogen sulfate and methanesulfonate anions were most effective in terms of lignin/cellulose fractionation and enhancement of cellulose digestibility.

Reusable Task‐Specific Ionic Liquids for a Clean ε‐Caprolactam Synthesis under Mild Conditions

Brønsted-acidic ionic liquids that bear a sulfonic acid group, known as Forbes acids, show a good catalytic activity for the Beckmann rearrangement, used to prepare ε-caprolactam, which is a precursor of Nylon 6. The activity essentially stems from the acidity of the sulfonic acid group. Although these task specific ionic liquids suffer from a high viscosity, this drawback can be circumvented at higher temperatures. A combination of the hydrogen sulfate anion and the sulfonic acid group of the cation is needed to obtain the rearrangement product rapidly under mild conditions. When using an excess of ionic liquid, we postulate that the internal pressure of the ionic medium, generated by the high viscosity and the high number of hydrogen-bonds, is strong enough to contribute to a decrease of the thermodynamic barrier. In accordance with the "Principles of Green Chemistry," we have developed a synthesis of ε-caprolactam that requires no additional chemicals except cyclohexanone oxime and the reusable TSIL.