Alkylated 1,4-diazabicyclo[2.2.2]octanes: self-association, catalytic properties, and biological activity

Aggregation of 1-hexadecyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide in the presence of diethyl 4-nitrophenyl phosphate was studied using ¹H NMR spectroscopy. The quantitative characteristics of the aggregation were determined. The data obtained were used to explain the catalytic effect of micelles on the hydrolysis of the phosphate. It was found that the aggregation properties and biological activity of alkylated mono- and dicationic 1,4-diazabicyclo-[2.2.2]octanes are correlated.     

Amphiphilic ionic liquid stabilizing palladium nanoparticles for highly efficient catalytic hydrogenation

The highly water-soluble palladium nanoparticles (NPs) were synthesized by using the amphiphilic poly(ethylene glycol)-functionalized dicationic imidazolium-based ionic liquid (C(12)Im-PEG IL) as a stabilizing agent. The aqueous dispersed palladium NPs in the range of 1.9 ± 0.3 nm were observed by transmission electron microscopy (TEM). The physicochemical properties of C(12)Im-PEG IL in aqueous phase have been characterized by electrical conductivity, surface tension and dynamic light scattering (DLS) measurements. It was demonstrated that the amphiphilic ionic liquid can form micelles above its critical micelle concentration (CMC) in aqueous solution and the micelles played a crucial role in stabilizing the palladium NPs and thus promoted catalytic hydrogenation. Furthermore, the dicationic ionic liquid can also act as a gemini surfactant and generated emulsion between hydrophobic substrates and the catalytic aqueous phase during the reaction. The aqueous dispersed palladium NPs showed efficient activity for the catalytic hydrogenation of various substrates under very mild conditions and the stabilizing Pd(0) nanoparticles (NPs) can be reused at least eight times with complete conservation of activity.     

Hydrolysis of bis(4-nitrophenyl) ethyl phosphate in micellar solutions of dicationic surfactants

The effect of dicationic surfactants on the hydrolysis of bis(4-nitrophenyl) ethyl phosphate in a borate buffer is studied. The presence of long-chain surfactants results in a significant (up to 50-fold) increase in the observed rate constant (k _obs) of the process. The catalytic effect of micelles increases with increasing alkyl chain length due to the strengthening of binding of the reagents by micelles. The presence of two cationic centers in the surfactant molecule enhances the catalytic properties of micelles. The dependence ofk _obs of hydrolysis of the substrate on the borate buffer concentration is studied. Alkaline hydrolysis is more sensitive to the added surfactant than the reaction involving borate ions.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1576–1580, September, 1994.     

Structure and properties of high stability geminal dicationic ionic liquids

Thirty-nine geminal dicationic ILs were synthesized and characterized in terms of their surface tensions, densities, melting points, refractive indices, viscosities, and miscibilities with a polar and nonpolar solvent. Two imidazolium or pyrrolidinium cations were joined via different length hydrocarbon linkage chains (from 3 to 12 carbons long). The various geminal dications were paired with up to four different anions. The effect of the dication type, linkage chain, alkyl substituents, and anion type on the physicochemical properties of these compounds was examined. Among the more interesting findings for this class of compounds was that their liquid and thermal stability ranges generally exceeded those of the more conventional, better known ILs. Indeed, this range was from -4 to >400 degrees C for one of the pyrrolidinium-based geminal dicationic liquids. X-ray crystallography of the smaller solid ionic compounds indicated that there may be a correlation between the configurational degrees of freedom of the ILs and their melting points/glass transition temperatures. In one case, the crystal structure showed that a dicationic moiety had three distinct conformations in an asymmetric unit cell. The solvation properties of the geminal dicationic ILs tend to be similar to those of their monocationic analogues.     

Vaporisation of a Dicationic Ionic Liquid Revisited

The vaporization of a dicationic ionic liquid at moderate temperatures and under reduced pressures —recently studied by line‐of‐sight mass spectrometry—was further analyzed using an ion‐cyclotron resonance mass spectroscopy technique that allows the monitoring of the different species present in the gas phase through the implementation of controlled ion–molecule reactions. The results support the view that the vapour phase of an aprotic dicationic ionic liquid is composed of neutral ion triplets (one dication attached to two anions). Molecular dynamics simulations were also performed in order to explain the magnitude of the vaporization enthalpies of dicationic ionic liquids vis‐à‐vis their monocationic counterparts.     

Solubilizing and catalytic properties of supramolecular systems based on gemini surfactants

Quantitative parameters characterizing the aggregation behavior of dicationic surfactants of the 12-s-12 type in aqueous solutions were determined: critical micelle concentrations, aggregation numbers, and surface potentials. The effects of the spacer length of the surfactants on their solubilizing effect with respect to hydrophobic (dye Orange OT) and water-soluble (p-nitrophenol) spectral probes and on their ability to shift acid-base equilibria were studied. The kinetics of alkaline hydrolysis of p-nitrophenyl acetate and p-nitrophenyl caprinate in 12-s-12 solutions was studied by spectrophotometry. A correlation between the micellar catalytic effect and the surface potential of micelles was established. The pronounced substrate specificity was revealed: the maximum acceleration of hydrolysis is observed in solutions of 12-6-12, attaining 1760 times for p-nitrophenyl caprinate.     

Mechanisms of TiO2 nanoparticle transport in porous media: role of solution chemistry, nanoparticle concentration, and flowrate

The controlled self-assembly of multi-components in one system represents the capability integrating intermolecular interactions and functions of components and is believed the key procedure leading to multifunctional materials finally. In pursuing this goal, we used a double-chain cationic surfactant with a benzoic acid group at the end of one tail to encapsulate Keggin-type polyanion clusters via electrostatic interaction, obtaining uniform supramolecular hybrid reverse micelles, which served as hydrogen-bonding donors. Five pyridine derivatives containing conjugated and non-conjugated groups were chosen as hydrogen-bonding acceptors to bind with reverse micelles. Through mixing with these components according to chemical stoichiometry, the hybrid reverse micelle changed to a new self-assembly precursor through intermolecular hydrogen bonding. The as-prepared reverse micelles bearing conjugated pyridine groups exhibit supramolecular liquid crystal properties, which were characterized by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. The length and number of the alky chain in the pyridine derivatives, as well as the charges of polyoxometalates were also studied with regard to the liquid crystal structure. The synergistic effect of among three components was analyzed, and the liquid crystal properties could be conveniently adjusted through the modification of the hydrogen-bonding acceptor components.     

Brønsted双核碱性离子液体的合成及其在制备生物柴油过程中的催化性能

以N-甲基吗啡啉和1,4-二溴丁烷为原料,通过两步法合成了新型Brønsted碱性双核离子液体.分别采用¹H-NMR、FT-IR和元素分析对合成的离子液体进行结构分析;采用TGA测试离子液体的热稳定性;同时测定了离子液体的溶解性和碱性.此外,考察了双核碱性离子液体在大豆油和甲醇酯交换反应中的催化活性.结果表明,当甲醇:大豆油=14:1(物质的量比)、离子液体用量为大豆油质量的5%、反应时间5 h、反应温度60 ℃时、生物柴油收率为 95.6%(质量分数),且离子液体经回收、真空干燥,重复使用6次后催化活性没有明显降低,仍能达到94%以上.     

Synthesis and characterization of a novel Brönsted acidic dicationic ionic liquid based on piperazine and its application in the one-pot synthesis of various xanthenes under solvent-free conditions

In this paper, an interesting Brönsted acidic dicationic ionic liquid based on piperazine was prepared via two-step synthesis. The structure of the dicationic ionic liquid (DIL) was confirmed with various techniques including Fourier transform infrared spectroscopy (FT-IR), Proton NMR (¹H NMR), Carbon-13 NMR (¹³C NMR), mass spectroscopy (MS), acid–base titration as well as Hammett acidity function. Catalytic activity of this novel Brönsted acidic DIL was examined in the xanthene synthesis. High yield of product, short reaction time, easily recovery and reusing of the catalyst, and the absence of organic solvents are some of the merits of the developed procedure.

     

两亲性嵌段共聚物的合成及其在离子液体中的自组装行为

采用阴离子开环聚合法合成了两亲性嵌段共聚物PLA-PEG-PLA.用FT-IR,1H NMR和GPC等手段对嵌段共聚物的结构组成进行了表征.两亲性嵌段共聚物在离子液体1-丁基-3-甲基咪唑六氟磷酸盐中能自组装成胶束,用透射电子显微镜观察了聚合物在离子液体中形成胶束的纳米结构.当疏水链长固定时,胶束的自组装形状主要依赖于亲水链的长度.两亲性共聚物在离子液体中可自组装成可控制结构的纳米胶束,这种纳米结构胶束在很多领域具有广泛的应用前景.     

Role of added counterions in the micellar growth of bisquaternary ammonium halide surfactant (14-s-14): 1H NMR and viscometric studies

The change in the morphology of a series of dicationic gemini surfactants C(14)H(29)(CH(3))(2)N(+)-(CH(2))(s)-N(+)(CH(3))(2)C(14)H(29), 2Br(-) (14-s-14; s=4-6) on their interaction with inorganic (KBr, KNO(3), KSCN) and organic salts (NaBenz, NaSal) have been thoroughly investigated by means of (1)H NMR spectral analysis and the results are well supported by viscosity measurements. The presence of salt counterions results in structural transition (spherical to nonspherical) of gemini micelles in aqueous solution. With an increase in salt concentration all the three gemini surfactants showed changes in their aggregate morphology. This change is dependent on the nature and size of the added counterion. The effect of inorganic counterions on the micellar growth is observed to follow the Hofmeister series (Br(-) < NO(3)(-) < SCN(-)). The roles of organic counterions are discussed on the basis of probable solubilization sites of the substrate molecule in the gemini micelles, showing more growth in case of Sal(-) than Benz(-). The results are confirmed in terms of the obtained values of chemical shift (δ), line width at half height (lw), and relative viscosity (η(r)). Also, the growth of micelles was most pronounced for the gemini surfactant with the shortest spacer (s=4). This was attributed to the unique molecular structure of gemini surfactant micelles having flexible polymethylene spacer chain linking the twin polar headgroups.     

Solubilization of triphenylamine, triphenylphosphine, triphenylphosphineoxide and triphenylmethanol in single and binary surfactant systems

Solubilization and co-solubilization of triphenyls (TPs) viz., triphenylphosphine (TPP), triphenylphosphineoxide (TPPO), triphenylamine (TPA) and triphenylmethanol (TPM) were studied in various single and binary surfactant systems at 25 °C using UV-visible spectroscopy and HPLC. The solubilization capacities of different micelles towards TPs were found to be a function of the nature and structure of solubilizates, locus of solubilization, size of micelles and the nature of interactions between the solubilizate and micelles. The effect of surfactant mixing on the solubilization of TPs was evaluated using the Regular Solution Approach (RSA). The solubility enhancement of TPs within mixed micelles relative to that observed in single surfactant systems was explained in light of the structural micellar changes associated with the mixing of ionic and non-ionic surfactants. Moreover, kinetics of oxidation of TPP by hydrogen peroxide investigated in these surfactant systems was found to be sensitive to the nature of micelle and the locus of solubilization of TPP within the micelles.     

Synthesis and optical properties of ZnO nanostructures in imidazolium-based ionic liquids

Different morphologies of ZnO nanostructures have been synthesized by a simple reflux method, in imidazolium-based ionic liquids and water as a solvent. The effects of ionic liquid as a template with different concentrations and the amount of sodium hydroxide on the morphology and size of nanostructures were investigated. The structural and optical properties of these ZnO particles were studied by using XRD, SEM and UV–Visible. The characteristic results revealed that using different ionic liquids in water not only prevent a drastic increase in the crystallite size of the zinc oxide species but also provide suitable conditions for the oriented growth of primary nanoparticles with nano sheet and nano hallow block. The results show that the longer alkyl chain at position-1 of imidazole ring or using dicationic ionic liquid with a definite concentration cause the more width of nano sheet. A possible mechanism was proposed to explain the formation of ZnO nanostructures with different morphology.     

Spectrometric and Voltammetric Characterization of Obidoxime in Aqueous Solutions

Obidoxime is a pharmacologically active compound used as an acetylcholinesterase reactivator. The scope of this study was to establish correlations between its acid–base and redox equilibria and its mechanism as an acetylcholinesterase reactivator. The obidoxime dicationic structure is modified by the pH of the solvating medium due to tautomeric isomerizations. The possibility of stabilizing its structure as a dicationic, monocationic, and a neutral species was studied by ultraviolet–visible spectrometry and cyclic and differential pulse voltammetry. Spectrometric and voltammetric studies were performed across a large pH interval (2.00–9.80) of the solvating medium. Absorption measurements revealed the existence of three species involved in two tautomeric equilibria implying oxime and nitroso groups. The structure bearing nitroso groups, stabilized at higher pH, is more likely to behave as a nucleophilic agent than the structure with oxime groups, explaining thus its acetylcholinesterase reactivation. The obidoxime voltammetric behavior at a glassy carbon electrode is complex. Both its oxidation and reduction are diffusion-controlled processes. Anodic signals were obtained only at pH values above 6.50 and the oxidation occurs at the anion oxime group involving two electrons and one proton. The obidoxime reduction is pH dependent only for neutral or alkaline media, giving rise to two or even four signals (for pH higher than 7.50) depending on pH. The peak at less positive potentials was always well defined.     

Supramolecular systems based on cationic surfactants and amphiphilic macrocycles

The effect of the structure of mono- and dicationic surfactants and amphiphilic calixarenes on their aggregation properties, aggregate morphology, and catalytic activity in reactions of nucleophilic substitution in esters is analyzed.     

A Novel Ionic Liquid Based on Imidazolium Cation as an Efficient and Reusable Catalyst for the One‐pot Synthesis of Benzoxazoles,Benzthiazoles, Benzimidazoles and 2‐Arylsubstituted Benzimidazoles

A novel dicationic ionic liquid based on imidazolium cation is designed, synthesized and successfully used as catalyst for the one‐pot synthesis of benzoxazoles, benzthiazoles, benzimidazoles and 2‐arylsubstituted benzimidazoles. The remarkable feature of this new catalyst is its ethyleneoxy bridge which participates in dissolving organic compound in ionic liquid. The application of this ionic liquid is studied in a new one‐pot method for synthesis of heterocyclic compounds under solvent‐free conditions. Simple and convenient procedure, high conversion, reusability of catalyst, easy purification and shorter reaction time are the advantageous features of this method.     

Acrylate functionalized tetraalkylammonium salts with ionic liquid properties

Acrylate functionalized ionic liquids based on tetraalkylammonium salts with terminal acrylates- and methylacrylates were synthesized. Melting points and ionic conductivity of twenty compounds in six groups were determined. Within one group the effect of three different counterions was investigated and discussed. The groups differ in cationic structure elements because of their functional groups such as acrylate and methacrylate, alkyl residues at the nitrogen and number of quaternary ammonium atoms within the organic cation. The effect of these cationic structure elements has been examined concerning the compiled parameters with a view to qualifying them as components for solid state electrolytes. The newly synthesized ionic liquids were characterized by NMR and FTIR analysis. The exchange of halide ions like bromide as counter ions to weakly coordinating [PF?]?, [OTf]? or [TFSI]? reduces the melting points significantly and leads to an ion conductivity of about 10?? S/cm at room temperature. In the case of the dicationic ionic liquid, an ion conductivity of about 10?3 S/cm was observed.     

Mass spectral evaluation of column bleeding for imidazolium-based ionic liquids as GC liquid phases

Mass spectra were obtained to evaluate the use of numerous single-cation and dicationic ionic liquids as stationary liquid phases in GC/MS at high temperature. Background mass spectra and product ion mass spectra of several ions in the background spectrum were obtained. Fragmentation mechanisms were propounded, including the detailed fragmentation pathway of the 1,2-dimethyl-3-propylimidazole cation. The relation between temperature and the main signals in the mass spectra of ILs was studied.     

Influence of the strong electrolyte on the aggregation behavior and catalytic properties of dicationic surfactants

The introduction of potassium chloride into an aqueous solution of dicationic (gemini) surfactants results in the partial neutralization of the surface charge of micelles, which is accompanied by an increase in their size, a decrease in the critical concentration of micelle formation, a decrease in the surface potential of the system, and a change in the micellar influence on the hydrolytic stability of solubilized carboxylic esters.