Kinds Of Room Temperature Ionic Liquids Research Articles

Electrochemical Behavior of Selenophene in Quaternary Ammonium and Phosphonium Based Ionic Liquids

Room-temperature ionic liquids (RTILs) have been regarded as potential electrolytic media for electropolymerization processes.1 Many kinds of RTILs have been investigated for the electropolymerizations. For example, we have reported that a bis(fluorosulfonyl)amide (FSA) anion based imidazolium ionic liquid promoted the electropolymerization reaction of pyrrole and the anion doping into the polymerized film, improving the conductivity of the film.2 We also have applied the phosphonium based RTILs to the electropolymerization of pyrrole and thiophene, investigating the influence of the phosphonium RTILs on the polymerized film properties.3 However, electrosynthesis of polyselenophene in phosphonium RTILs has not been examined. In this work, we report the electropolymerization of selenophene in triethylpentylphosphonium FSA (P2225-FSA) (Fig. 1) and the effect of the phosphonium RTIL on the polyselenophene film properties. P2225-FSA was prepared according to the procedure we have previously reported,4 and dried under high vacuum at 80°C for 6 h before use. The electropolymerization of selenophene in P2225-FSA was carried out by cyclic voltammetry (CV) method using a three-electrode cell equipped with a working electrode of platinum or transparent glass electrode and an IL-based Ag/Ag+ reference electrode. Figure 2 showed the cyclic voltammograms for the electropolymerization of selenophene in P2225-FSA. In the first cycle, the oxidation peak current value of about 0.2 mA was shown around +1.7 V vs Ag/Ag+, and the current decayed with each cycle. This closely resembles the electrochemical behavior observed in CVs using π-conjugated aromatic compounds such as pyrrole and thiophene as substrates. 3 After 10 cycles, a black thin film was grown on the surface of the working electrode, and the oxidation current observed in this CV seems to be due to the electropolymerization reaction of selenophene. Furthermore, we will discuss the comparison between the behaviors in various quaternary onium based ionic liquids from the viewpoint of the morphology of the polymer film grown on the working electrode. References K. Sekiguchi, et al, J. Electroanal. Chem. , 1, 557 (2003).K. Tsunashima, et al, ECS Electrochem. Lett., 3, G1 (2014).K. Nishihata, et al, ECS Trans., 75, 99 (2016).K. Tsunashima, et al, Electro cheml. Commun. , 13, 178 (2011). Figure 1

Electropolymerization of Thiophene in a Bis(fluorosulfonyl)Amide Based Phosphonium Ionic Liquid

Room-temperature ionic liquids (RTILs) have been regarded as potential electrolytic media for electropolymerization processes.1 Many kinds of RTILs have been investigated for the electropolymerizations. For example, we have reported that a bis(fluorosulfonyl)amide (FSA) anion based imidazolium ionic liquid promoted the electropolymerization reaction of pyrrole and the anion doping into the polymerized film, improving the conductivity of the film.2 We also have applied the phosphonium based RTILs to the electropolymerization of pyrrole, investigating the influence of the phosphonium RTILs on the polymerized film properties.3 However, electrosynthesis of polythiophene in phosphonium RTILs has not been examined. In this work, we report the electropolymerization of thiophene in triethylpentylphosphonium FSA (P2225-FSA) and the effect of the phosphonium RTIL on the polythiophene film properties.P2225-FSA was prepared according to the procedure we have previously reported,4 and dried under high vacuum at 80°C for 6 h before use. The electropolymerization of thiophene in P2225-FSA was carried out by cyclic voltammetry (CV) method using a three-electrode cell equipped with a working electrode of platinum or transparent glass electrode and an IL-based Ag/Ag+ reference electrode.Fig. 1 showed the cyclic voltammograms for the electropolymerization of thiophene in P2225-FSA. It was found that an irreversible oxidation peak was observed and maintained even when the cycle was repeated, forming the polythiophene film on the electrode surface. It is noted that the peak current at 2.2 V vs Ag/Ag+ was enhanced by cycling, which seems likely to be attributed to the efficient anion doping into the polymerized film grown on the working electrode surface. Fig. 2 depicted a SEM image of the polythiophene film grown in P2225-FSA. A uniform surface of the film grown in P2225-FSA was observed when compared to that in an organic solvent based electrolyte, which is closely similar to the result previously found in the electropolymerization of pyrrole. The electrochemical activity and thermal stability of the polythiophene film obtained will be discussed.

Electrooxidative Polymerization of Aniline in Phosphonium Ionic Liquids and Characterization of the Polyaniline Films

Room-temperature ionic liquids (RTILs), i.e. organic molten salts with melting points below 100 ◦C, have been intensively developed for electrolytic media in various electrochemical systems due to the fact that RTILs have unique physicochemical properties such as favorable solubility of organic and inorganic compounds, relatively high ionic conductivity, no measurable vapor pressure, high thermal stability, low flammability, etc. Particularly, RTILs have been regarded as potential electrolytic media for electropolymerization processes.1 Many kinds of RTILs have been investigated for the electropolymerizations; however, highly conductive and stable RTILs based on quaternary phosphonium cations2 have been rarely employed for this application. In this work, we report the electrooxidative polymerization of aniline in triethylpentylphosphonium bis(trifluoromethylsulfonly)amide (P2225-TFSA) and tributylmethylphosphonium bis(trifluoromethylsulfonly)amide (P4441-TFSA) in comparison with the other type of RTILs, characterizing the obtained polyaniline films. The preparation of the phosphonium RTILs was performed by aqueous ion exchange reaction of the precursor quaternary phosphonium halides with lithium TFSA. The electrooxidative polymerization of aniline in phosphonium RTILs containing 0.1 M H-TFSA was carried out by cyclic voltammetry (CV) method using a three-electrode cell equipped with a Pt disk working electrode. The electrochemical activity of the polyaniline films were evaluated by extended CV scanning technique.Figure 1 shows typical cyclic voltammograms for the electrooxidative pocesses of aniline. As shown in Fig. 1, it was found that relatively large voltammetric response was observed in P2225-TFSA when compared to that in P4441-TFSA. This seems to be attributed to the relatively low viscosity and high conductivity of P2225-TFSA. In addition, the voltammetric responses were enhanced by cycling, which indicates that ionic species could be efficiently doped into the polyaniline film. The surface morphology based on SEM images of the polyaniline films will be also discussed.References 1 K. Sekiguchi, et al, J. Electroanal. Chem. , 557, 1 (2003).2 K. Tsunashima, et al, Electrochem. Commun., 9, 2353 (2007). Figure 1

Tetracyanoborate Anion Based Phosphonium Ionic Liquids As Electrolytes for Pyrrole Electropolymerization

Room-temperature ionic liquids (RTILs) have been regarded as potential electrolytic media for electropolymerization processes.1 Many kinds of RTILs have been investigated for the electropolymerizations; however, RTILs based on tetracyanoborate (B(CN)4 -, TCB) anion have been rarely employed. On the other hand, we have designed quaternary phosphonium RTILs exhibiting high transport property and high stability.2 In this work, we report the physicochemical and electrochemical characterization of the phosphonium RTILs based on the TCB anion (Fig. 1) as electrolytes for electropolymerization of pyrrole (Py).The preparation of the TCB-based phosphonium RTILs was performed by aqueous ion exchange reaction of the precursor quaternary phosphonium halides with sodium tetracyanoborate (Na-TCB). Residual metal and halide ions in the clude RTILs were removed by a silica gel column. The combination of the asymmetric phosphonium cations with TCB anion successfully gave liquids at ambient temperature. The TCB-based phosphonium RTILs showed thermal decomposition temperatures at more than approximately 400°C. The electropolymerization of Py in the TCB-based phosphonium RTILs was carried out by cyclic voltammetry (CV) method. Fig. 2 showed the cyclic voltammograms for the electropolymerization of Py in P2225-TCB. It was found that an irreversible oxidation peak was observed and maintained when the cycle was repeated, giving the PPy films on the electrode surface. As shown in Fig. 3, the SEM images of the PPy films exhibited the relatively uniform surface when compared to the PPy films grown in the corresponding bis(fluorosulfonyl)amide-based phosphonium RTILs. The thermal stability of the PPy film grown in the TCB-based phosphonium RTILs will be also discussed.References 1 K. Sekiguchi, et al, J. Electroanal. Chem. , 557, 1 (2003).2 K. Tsunashima, et al, Electrochem. Commun., 9, 2353 (2007). Figure 1

Effects of Water on Solvation Layers of Imidazolium-Type Room Temperature Ionic Liquids on Silica and Mica.

Effects of the addition of water on solvation layers of imidazolium-type room temperature ionic liquids (RT-ILs) have been studied through force curve measurements of atomic force microscopy (AFM). Two kinds of RT-ILs were employed in this study; one is a hydrophilic RT-IL (1-butyl-3-methylimidazolium tetrafluoroborate, BmimBF4), and the other is a hydrophobic one (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, EmimTFSI). These RT-ILs form solvation layers on hydrophilic solid substances (i.e., silica and mica) in the absence of added water. The addition of water into BmimBF4 resulted in the disruption of the solvation layers and then the formation of an interfacial water phase on silica. In contrast, the formation of the interfacial water phase was not evidenced on mica because of the absence of hydrogen-bonding sites on the mica surface. Interestingly, the addition of water into EmimTFSI induced the formation of the interfacial water phase on the two solid surfaces. In the EmimTFSI system, importantly, significantly greater adhesion forces were observed on silica than on mica. This reflects the different formation mechanisms of the interfacial water phase on the two solid surfaces. We conclude that the hydrogen bonding is a key factor in determining whether water molecules can be adsorbed on the solid surfaces, but it is also necessary to take into account the hydrophilic/hydrophobic nature of the RT-ILs.

Physical and Electrochemical Properties of Room-Temperature Ionic Liquids Containing Allyl-Based Phosphonium Cations and Bis(fluorosulfonyl)Amide Anion

Room-temperature ionic liquids (RTILs) have been developed for a wide variety of electrochemical applications due to their unique physicochemical properties such as favorable solubility of organic and inorganic compounds, relatively high ionic conductivity, no measurable vapor pressure, high thermal stability, low flammability, etc. Another advantage of RTILs is a designability of the chemical structures. Although many kinds of RTILs have been already investigated, interests in phosphonium RTILs have been increasing for their considerable advantages such as chemical and thermal stabilities. Recently, we have designed and proposed several RTILs based on quaternary phosphonium cations together with a bis(fluorosulfonyl)amide (N(SO2F)2 -, FSA) anion.1 We also reported several phosphonium RTILs containing unsaturated carbon-carbon bonds in combination with a bis(trifluoromethylsulfonyl)amide (N(SO2CF3)2 -, TFSA) anion.2 In this work, we demonstrate the physicochemical characterizations of the RTILs based on quaternary phosphonium cations containing an allyl group (Figure 1) together with a FSA anion.The preparation and purification of phosphonium RTILs were carried out according to the procedures described in our previously published papers.1,2 The phosphonium RTILs were prepared by aqueous ion exchange reactions of the precursor phosphonium bromides with lithium TFSA or potassium FSA. The resulting crude RTILs was extracted by dichloromethane, and then purified by washing with pure water several times until no residual bromide anion was detected with the use of AgNO3. The RTILs was dried under high vacuum for at least 8 h at 100 ◦C prior to use. The physicochemical and electrochemical properties such as conductivity (ac impedance method), viscosity (cone-plate type viscometer), density, melting point (DSC), thermal decomposition temperature (TGA) and electrochemical window (linear sweep voltammetry, LSV) were measured under dry argon atmosphere.Table 1 summarizes the physicochemical properties of the allyl-based phosphonium RTILs together with a FSA anion. When an allyl group was introduced into an alkyl chain of the phosphonium cation, such phosphonium RTILs exhibited lower viscosity and higher conductivity than the corresponding unsubstituted phosphonium RTILs. Similar results were obtained in the case of TFSA-based phosphonium RTILs.2 In this series of RTILs, P111(Al)-FSA showed the highest density, lowest viscosity and highest conductivity because of its smallest cation size. In addition, it was found that each RTIL showed lower melting point than that of the corresponding TFSA-based RTILs. This finding reveals that the combination of the phosphonium cations with FSA anion expands the temperature range of the RTILs. The electrochemical analysis by using a LSV technique suggested that the electrochemical windows tended to be somewhat reduced by introducing an allyl group; however, lithium deposition and dissolution in the RTILs was possible. The influence of the introduction of an allyl group on the thermal stability of the RTILs will be also reported and discussed.

Probing the adsorption of methylimidazole at ionic liquids/Cu electrode interface by surface‐enhanced Raman scattering spectroscopy

AbstractTwo kinds of room‐temperature ionic liquids, 1‐butyl‐3‐methylimidazolium bromide ([BMIM]Br) and 1‐butyl‐3‐methylimidazolium tetrafluoroboride ([BMIM]BF4), were used as solvent, and the adsorption of the ionic liquids themselves and of N‐methylimidazole (NMIM) were investigated by electrochemical surface‐enhanced Raman scattering (SERS) over a wide potential window. The results revealed that the cation of ionic liquid adsorbed onto Cu surface with different configurations in different potential ranges. When the potential was changed from the negative to the positive range, the orientation underwent a change from flat to vertical, and the onset potential for the orientation change was dependent on the types of anion of the ionic liquid. The ionic liquid in bulk solution exhibited a remarkable effect on the adsorption of NMIM. The electrode surface structure changed from adsorbing the ionic liquid at the negative potential to coadsorbing the ionic liquid and NMIM at relative positive potential for the [BMIM]BF4 liquids, and formed films of NMIM at extremely positive potential. Due to the strong specific adsorption of Br−, the coadsorption of ionic liquid and NMIM was not observed in the system [BMIM]Br. By simulating the electrode surroundings, two surface complexes [Cu(NMIM)4Br]Br·H2O and [Cu(NMIM)4](BF4)2 were synthesized by the electrochemical method in the corresponding ionic liquids for modeling the surface coordination chemistry of NMIM. The surface coordination configuration of NMIM and ionic liquids is proposed. Copyright © 2009 John Wiley & Sons, Ltd.

Characterization Studies on the Ionic Liquid-Templated Mesoporous Silica with Wormlike Pores

This article reports a novel preparation of wormlike mesoporous silica with 1-hexadecane-3-methylimidazolium bromide (C16MIM)Br, a kind of room-temperature ionic liquids (RTILs), as a template via a sol-gel nanocasting technique. The characterization studies were carried out in contrast with that of the mesoporous silica with cetyltrimethylammonium bromide (CTAB), a usually used template, which has the same alkyl chain length with (C16MIM)Br. The structures of the silica materials have been characterized by Transmission electron microscopy (TEM), High-resolution TEM (HRTEM) and N2 adsorption-desorption measurements. The results show that both the mesoporous materials prepared with different templates respectively can form regular wormlike mesopores with ca. 2 nm in pore diameter. They also have large BET surface areas with narrow size distribution. Compared to the CTAB-template mesoporous silica, the material with (C16MIM)Br as a template has highly uniform pore size and larger surface area. In addition, the formation mechanism of the wormlike mesopores with RTIL has been proposed by an electrostatic charge matching assembly-pathway and steric factor.

Property of ionic liquid in electrophoresis and its application in chiral separation on microchips

The aqueous solution of a kind of room-temperature ionic liquids (RTILs), 1-ethyl-3-methylimidazolium-tetrafluoroborate (1E-3MI-TFB), demonstrated its exclusive electroosmotic property in microchip electrophoresis. It was applied as the working electrolyte for chiral separation in glass microchip electrophoresis. Compared with boric acid buffer, 1E-3MI-TFB aqueous solution exhibited a broader separation window for enantiomers of dipeptides. Then the influences of chiral selector, pH and concentration on efficiency of chiral separation were discussed in detail. The unique mechanism of the generation of EOF was explored in a glass microchannel using 1E-3MI-TFB aqueous solution as working electrolyte. A possible status of 1E-3MI cation in water was suggested at the first time, which facilitated the explanation of EOF and its characteristics in glass microchannel. Additionally, microchip electrophoresis using 1E-3MI-TFB aqueous solution was successfully applied to the chiral separation of complex enantiomers of dipeptides. RTILs aqueous solution, as the electrolyte for the separation of complicated optical isomers, could lead to a revolution in the analytical methods of chiral or conformational analysis for biomolecules.

Synthesis of Chloroaluminate Ionic Liquids and Use for Olefin Reduction in FCC Gasoline

Room temperature ionic liquids (RTILs) are mainly referred to melting salt systems composed by organic cations and organic or inorganic anions that exhibit liquid-like behavior at or around room temperature. Chloroaluminate room temperature ionic liquid (chloroaluminate RTILs) is one kind of RTIL synthesized by chloride quaternary ammonium salts and anhydrous AlCl3. Three kinds of chloroaluminate RTILs were synthesized using trimethylamine hydrochloride (TA), 1-butylpyrinium chloride (BPyC), or 1-methyl-3-alkylimidazolium (BMIC), respectively, with anhydrous AlCl3 and their application in reducing the content of olefin in FCC gasoline from the Jinzhou Petrochemical Corporation was studied. The effects of chloroaluminate RTIL component and operation conditions on olefin reduction were investigated as well as the repeatability of chloroaluminate RTILs. The results show that at room temperature, when the ratio of anhydrous AlCl3 to quaternary ammonium (mole/mole), the solvent-oil ratio (g/g), and the reaction time were 2/1, 20/100, and 1/2 h, respectively, the content of olefin in FCC gasoline was deduced more than 30%. The chloroaluminate RTILs could be used at least four times on the basis of keeping their activity.

Complex Extraction of Thiophenes Using Room Temperature Ionic Liquids

Two kinds of room temperature ionic liquids (RTILs) 1-butyl-3-methyl limidazolium chloroaluminate (III) ([bmim]Cl+AlCl3) and 1-butyl-3-methyl limidazolium hexfluorophosphate ([bmim]PF6) were synthesized, respectively, and the removal of thiophenes from refined diesel was studied by the method of complex extraction. The results showed that under the best operational conditions, the content of thiophenes went down 46 wt% in chloroaluminate RTIL and 69 wt% in hexfluorophosphate RTIL, and other properties of diesel were improved at the same time. Both of the two kinds of RTILs can be used for several times through regenerating.

New Force Field for Molecular Simulation of Guanidinium-Based Ionic Liquids

An all-atom force field was proposed for a new class of room temperature ionic liquids (RTILs), N,N,N',N'-tetramethylguanidinium (TMG) RTILs. The model is based on the AMBER force field with modifications on several parameters. The refinements include (1) fitting the vibration frequencies for obtaining force coefficients of bonds and angles against the data obtained by ab initio calculations and/or by experiments and (2) fitting the torsion energy profiles of dihedral angles for obtaining torsion parameters against the data obtained by ab initio calculations. To validate the force field, molecular dynamics (MD) simulations at different temperatures were performed for five kinds of RTILs, where TMG acts as a cation and formate, lactate, perchlorate, trifluoroacetate, and trifluoromethylsulfonate act as anions. The predicted densities were in good agreement with the experimental data. Radial distribution functions (RDFs) and spatial distribution functions (SDFs) were investigated to depict the microscopic structures of the RTILs.