Guanidinium-based Ionic Liquids Research Articles

Guanidinium-Based Ionic Liquids for High-Performance SO2 Capture and Efficient Conversion for Cyclic Sulfite Esters

Guanidinium-Based Ionic Liquids for High-Performance SO₂ Capture and Efficient Conversion for Cyclic Sulfite Esters

Carbon Dioxide Solubility in Guanidinium-Based Ionic Liquids at High Pressure

Carbon Dioxide Solubility in Guanidinium-Based Ionic Liquids at High Pressure

Surface-confined guanidinium ionic liquid as a new type of stationary phase for hydrophilic interaction liquid chromatography.

Guanidinium-based ionic liquids possess lower toxicity and greater designability than commonly used species and have presented good performances in liquid-phase extraction and stationary phase for capillary gas chromatography. In the present work, a novel type of surface-confined guanidinium ionic liquid stationary phase was developed by bonding a hexaalkylguanidinium ionic liquid N,N,N',N'-tetramethyl-N",N"-diallylguanidinium bromide onto the surface of 3-mercaptopropyl modified silica. The obtained surface-confined guanidinium ionic liquid silica materials were characterized by elemental analysis, infrared spectroscopy and thermogravimetric analysis, and then packed as a high-performance liquid chromatography column for the evaluation of chromatographic retention behavior. Typical polar compounds were used to evaluate the separation performances, and the changes of retention with water content in mobile phase further suggested the hydrophilic interaction liquid chromatography retention mechanism. Moreover, the effect of different chromatographic factors (salt concentration, mobile phase pH, and column temperature) on retention was investigated with a series of compounds as test solutes to gain insights into the retention mechanism. The results indicated that the surface-confined guanidinium ionic liquid stationary phase exhibited a hydrophilic interaction liquid chromatography/anion-exchange mixed-mode retention behavior and possessed promising potential in separating a wide range of compounds as an alternative stationary phase for high-performance liquid chromatography.

Structural Arrangement and Computational Exploration of Guanidinium-Based Ionic Liquids with Benzoic Acid Derivatives as Anions

Crystallization of ionic liquids (ILs) is of great interest for determining the crystal structure and molecular interactions. Hydrogen bonding is an important noncovalent interaction, which is rela...

Synthesis, properties of pentaalkylguanidinium-based magnetic room temperature ionic liquids (MRTILs) and the mutual solubility of (MRTILs + cyclohexane) and (MRTILs + n-octane) binary systems

The application of guanidinium-based ionic liquids (ILs) is a newly emerging area in the fields of extraction desulfurization. Herein, four novel pentaalkylguanidinium-based magnetic room temperature ionic liquids (MRTILs) [CnTMG][FeCl3Br] (n = 2, 4, 6, 8) were synthesized and characterized by FT-IR, Raman and HRMS (ESI) spectra. The physical properties including thermal stability, density, viscosity, conductivity and magnetic properties were determined and revealed that the MRTILs were liquids at room temperature and have good thermal stability (Td > 250 °C), high magnetic susceptibility (>3.8 × 105 emu·g−1) and low viscosities (<160 mPa·s, 25 °C). Moreover, the mutual solubility behaviors for binary systems of MRTILs with representative non-polar organic solvents (cyclohexane, n-octane) were measured at temperatures from 5 to 65 °C, showed a low miscibility between MRTILs and organic solvents and a typical lower critical solution temperature (LCST) phenomenon. The results are supposed to provide useful information for further application as “green” liquid desulfurization extractants or others potential dispersive liquid-liquid microextraction applications.

Antimicrobial activity and cytotoxicity of piperazinium- and guanidinium-based ionic liquids

Twelve piperazinium- and guanidinium-based ionic liquids (ILs) were synthesized, and characterized by 1H nuclear magnetic resonance (NMR), thermal gravimetric analyzer (TGA) and differential scanning calorimetry (DSC). The antimicrobial activity and cytotoxicity have been investigated to provide the information whether the newly synthesized ILs are toxic or not. The antimicrobial effects of these ILs on gram negative and gram positive bacteria are evaluated on the basis of the minimum inhibitory concentration (MIC) measurements. The membrane damages of bacteria in the presence of ILs are observed by scanning electron microscopy (SEM). The cytotoxicity data of the ILs on HEK-293 and C6 cells are obtained by MTT cell viability assay. The disruption of cell cycle is analyzed by the flow cytometry. The results show that most of the ILs exhibit low toxicity, and the ILs with tetrafluoroborate anion and with benzene ring on cation are the species with relatively high toxicity among the studied ILs. The fundamental data and results can provide some useful information for the further studies and applications of the ILs.

Catalytic performance of a series of guanidinium-based ionic liquids in the coupling reaction of carbon dioxide with epoxides

The cycloaddition reaction of CO2 into EO, catalyzed by a series of functional guanidinium-based ionic liquids, is schematically studied by the DFT.

Densities and Viscosities of Binary Mixtures of 2-Ethyl-1,1,3,3-tetramethylguanidinium Ionic Liquids with Ethanol and 1-Propanol

Two guanidinium-based ionic liquids (ILs), 2-ethyl-1,1,3,3-tetramethylguanidinium bis(trifluoromethylsulfonyl)imide ([TMGEt][NTf2]) and ethyl sulfate ([TMGEt][C2OSO3]) were synthesized and characterized. Experimental densities and viscosities for the binary mixtures of the ILs with ethanol and 1-propanol from (293.15 to 323.15) K were measured over the whole composition range and at the atmospheric pressure of 0.1 MPa. The excess molar volumes (VmE) and the viscosity deviations (Δη) for the binary systems were calculated and fitted with the Redlich–Kister equation. It is found that the density of [TMGEt][NTf2] is much higher than that of [TMGEt][C2OSO3] at the same temperature, while the viscosity of the former with the value of 74.61 mPa·s is only 1/9 of that of the latter at 293.15 K. This indicates that the difference of the anions has a significant influence on the density and viscosity of the ILs with the same guanidinium cation. The addition of ethanol or 1-propanol leads to negative values of VmE a...

Novel Guanidinium-Based Ionic Liquids for Highly Efficient SO2 Capture.

The application of ionic liquids (ILs) for acidic gas absorption has long been an interesting and challenging issue. In this work, the ethyl sulfate ([C2OSO3](-)) anion has been introduced into the structure of guanidinium-based ILs to form two novel low-cost ethyl sulfate ILs, namely 2-ethyl-1,1,3,3-tetramethylguanidinium ethyl sulfate ([C2(2)(C1)2(C1)2(3)gu][C2OSO3]) and 2,2-diethyl-1,1,3,3-tetramethylguanidinium ethyl sulfate ([(C2)2(2)(C1)2(C1)2(3)gu][C2OSO3]). The ethyl sulfate ILs, together with 2-ethyl-1,1,3,3-tetramethylguanidinium bis(trifluoromethylsulfonyl)imide ([C2(2)(C1)2(C1)2(3)gu][NTf2]) and 2,2-diethyl-1,1,3,3-tetramethylguanidinium bis(trifluoromethylsulfonyl)imide ([(C2)2(2)(C1)2(C1)2(3)gu][NTf2]), are employed to evaluate the SO2 absorption and desorption performance. The recyclable ethyl sulfate ILs demonstrate high absorption capacities of SO2. At a low pressure of 0.1 bar and at 20 °C, 0.71 and 1.08 mol SO2 per mole of IL can be captured by [C2(2)(C1)2(C1)2(3)gu][C2OSO3] and [(C2)2(2)(C1)2(C1)2(3)gu][C2OSO3], respectively. The absorption enthalpy for SO2 absorption with [C2(2)(C1)2(C1)2(3)gu][C2OSO3] and [(C2)2(2)(C1)2(C1)2(3)gu][C2OSO3] are -3.98 and -3.43 kcal mol(-1), respectively. While those by [C2(2)(C1)2(C1)2(3)gu][NTf2] and [(C2)2(2)(C1)2(C1)2(3)gu][NTf2] turn out to be only 0.17 and 0.24 mol SO2 per mole of IL under the same conditions. It can be concluded that the guanidinium ethyl sulfate ILs show good performance for SO2 capture. Quantum chemistry calculations reveal nonbonded weak interactions between the ILs and SO2. The anionic moieties of the ILs play an important role in SO2 capture on the basis of the consistently experimental and computational results.

Challenges for Unique Application of Ionic Liquids as a Novel Initiator of Radical Polymerization

In this study, the author has investigated the polymerization of styrene (St), methyl methacrylate, and methyl acrylate initiated with guanidinium-based ionic liquids such as guanidinium tris(pentafluoroethyl)trifluorophosphate ([gua]e3fap), guanidinium trifluoromethanesulfonate, N,N,N′N′-tetramethyl-N′′-ethylguanidinium tris(pentafluoroethyl)trifluorophosphate, and N,N,N′N′-tetramethyl-N′′-ethylguanidinium trifluoromethanesulfonate to elucidate the new possibility of ionic liquids as an initiator of radical polymerization. For example, the polymerization of St initiated with [gua]e3fap proceeded at 70°C under air and under argon. It was strongly suggested that the St-polymerization initiated with [gua]e3fap proceeds via a radical pathway, because the inhibitory effects of 2,6-di-tert-butyl-p-cresol and hydroquinone as a radical inhibitor and 1-dodecanethiol as a radical chain transfer agent were observed.

Synthesis and Characterization of Guanidinium-Based Ionic Liquids as Possible Electrolytes in Lithium-Ion Batteries

Two guanidinium-based ionic liquids (ILs), N-cyclohexyl-N,N′,N′,N″,N″-pentamethylguanidinium bis(trifluoromethylsulfonyl) imide (Me5cHexGua-TFSI) and N,N-bis(2-ethylhexyl)-N′,N′,N″,N″-tetramethylguanidinium bis(trifluoromethylsulfonyl)imide (Me4(2-EtHex)2Gua-TFSI), were synthesized and investigated for their applicability as electrolyte components for lithium-ion batteries. Various properties, such as conductivity, viscosity, potential window at a platinum electrode and eventually the compatibility with graphite, Li4Ti5O12 (LTO) and LiFePO4 (LFP) electrodes were determined for the neat ILs and for electrolytes from these ILs with 0.3 mol/kg LiTFSI as conductive salt. The viscosities of the neat guanidinium-based ILs are 385 mPas and 683 mPas at 23°C for Me5cHexGua-TFSI and Me4(2-EtHex)2Gua-TFSI, respectively, and the conductivities are 0.67 and 0.18 mS/cm at 25°C. In the presence of 0.3 mol/kg LiTFSI the conductivities decreased to 0.29 and 0.10 mS/cm, respectively. Both ILs reached anodic stabilities of 4.8 V vs. Li/Li+ and showed cathodic stabilities of 0.6 V vs. Li/Li+. The guanidinium-based electrolytes can be applied with LTO and LFP electrodes, but are not compatible with graphite electrodes. The results obtained for guanidinium-based ILs/electrolytes are compared with those of a carbonate-based electrolyte [1 M LiPF6 in EC:DMC (1:1, w/w)], and a pyrrolidinium-based IL/electrolyte [1-butyl-1-methylpyrrolidinium-TFSI (BMPL-TFSI) and 0.3 mol/kg LiTFSI in BMPL-TFSI].

Investigation of New Guanidinium-Based Ionic Liquids As Possible Electrolytes in Lithium-Ion Batteries

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Novel functionalized guanidinium ionic liquids: Efficient acid–base bifunctional catalysts for CO2 fixation with epoxides

A series of functional guanidinium-based ionic liquids (FGBILs) that contain both Lewis acid and basic sites was prepared by a simple method, and used as catalysts for the synthesis of cyclic carbonates through the cycloaddition of CO2 to epoxides in the absence of co-catalyst and solvent. Propylene oxide conversion was near completion at 130°C and 2.5MPa in 2h when [TMGC2H4NH2]Br was used as catalyst. The effects of functional groups and counter anions on catalytic performance were investigated. The synergistic effect of polarization by hydrogen bonding and the nucleophilic attack by bromide anion account for the facile ring-opening of epoxide. Furthermore, the protocol is applicable to a variety of terminal epoxides, producing the corresponding cyclic carbonates in high yield and selectivity. It is envisaged that the metal- and solvent-free process using a single catalyst has high potential for large-scale fixation of CO2.

Separation performance of guanidinium-based ionic liquids as stationary phases for gas chromatography

Room temperature ionic liquids (RTILs) as stationary phases for gas chromatography (GC) have made great achievements in both research and applications over the last decades. Until now, all of the RTIL stationary phases reported have involved imidazolium, ammonium, pyrrolidinium, and phosphonium-based RTILs, and however, no publications are available using guanidinium-based ionic liquids (GBILs) as GC stationary phases except two preliminary reports from our group. In the present work, three hexaalkyl GBILs stationary phases, namely N, N,N′,N′-tetramethyl-N″, N″-dioctylguanidinum hexafluophosphate (DOTMG-PF6), N,N,N′,N′-tetramethyl-N″, N″-dioctylguanidinium bis (trifluoromethylsulfonyl) imide (DOTMG-NTf2), and N,N,N′,N′-tetraoctyl-N″, N″-dimethylguanidinium bis (trifluoromethylsulfonyl) imide (TODMG-NTf2), were synthesized and used as stationary phases for GC separation after they were statically coated onto the inner walls of fused-silica capillary columns. The evaluation of DOTMG-PF6 and TODMG-NTf2 as GC stationary phases is reported here for the first time, whereas additional results on the DOTMG-NTf2 stationary phase are added here on the basis of our previous report. In this work, McReynolds constants and Abraham solvation system constants are used to evaluate the average polarity and the solvation properties of the GBILs stationary phases for GC separation, respectively. The results show that the GBILs stationary phases exhibit medium polarity with an average polarity of 293–390, and that the major molecular interactions of the GBILs with analytes are dipole/polarizable interactions, H-bond basicity and dispersion forces, etc. After this, the separation performance and thermal stability of the GBILs stationary phases were evaluated, showing that these stationary phases achieve excellent separation for analytes of great variety covering hydrocarbons, alcohols, esters, aldehydes, ketones, amines, amides and aromatics, and exhibit different retention behaviors from the most widely used GC stationary phases such as polyethylene glycol (PEG-20M) and 5% phenyl–95% dimethylpolysiloxane (SE-54) in terms of resolution and elution order, and good thermal stability (at least up to 250°C). The present work demonstrates that the GBILs stationary phases possess excellent separation performance and thermal stability, and may be applicable as a new type of GC stationary phases for separation of complex samples.

All-atom and united-atom simulations of guanidinium-based ionic liquids

Ionic liquids (ILs) have been widely used in separation, catalysis, electrochemistry, etc., and one of the most outstanding characteristics is that ILs can be tailored and tuned for specific tasks. In order to design and make better use of ionic liquids, the structures and properties relationship is indispensable. Both molecular dynamics and Monte Carlo simulations have been proved useful to understand the behavior of molecules at the microscale and the properties of the system. However, the quality of such simulations depends on force field parameters describing the interactions between atoms. All-atom (AA) or the united-atom (UA) force fields will be chosen because of the demand for more exact results or the lower computational cost, respectively. In order to make a systematic comparison of the two force fields, molecular simulations for four kinds of acyclic guanidinium-based ionic liquids (cations: (R2N)2C=N+<, anion: nitric or perchloric acid) were performed based on the AA and the UA force fields in this work. AA force field parameters were derived from our previous work (Fluid Phase Equilib., 2008, 272: 1–7), and the UA parameters were proposed in this work. Molecular dynamics simulation results for the AA and UA force fields were compared. Simulation densities are very similar to each other. Center of mass radial distribution functions (RDFs), site to site RDFs and spatial distribution functions (SDFs) were also investigated to depict the microscopic structures of the ILs.

Guanidinium-based ionic liquids for sulfur dioxide sorption

Three guanidinium-based ionic liquids (GBILs) including [1,1,3,3-tetramethylguanidinium][phenol] ([TMG][PHE]), [1,1,3,3-tetramethylguanidinium][2,2,2-trifluoroethanol] ([TMG][TE]) and [1,1,3,3-tetramethylguanidinium][imidazole] ([TMG][IM]) were synthesized and their absorption and desorption of sulfur dioxide were investigated, respectively. The saturated molar ratio of SO 2 to GBILs varied from 2.24 to 3.16 at 40 °C with high absorption rate. The absorption mechanism might be that SO 2 reacts with the –NH 2 group on the cation and then a new –SO 2H group is formed. The new GBILs could absorb SO 2 by both physical and chemical interactions while physical absorption does play an important role at the experimental conditions under investigation.

Guanidinium‐Based Phosphotungstates and Ionic Liquids as Catalysts and Solvents for the Epoxidation of Olefins with Hydrogen Peroxide

AbstractSeveral penta‐ and hexaalkylated guanidinium‐based ionic liquids (GILs) were tested as solvents for the epoxidation of cyclooctene using the Venturello catalyst, [(C8H17)3N(CH3)]3[PO4{WO(O2)2}4], and hydrogen peroxide as the oxidant. Epoxide yields were obtained in a broad range between 13 and 79 % depending on both the anion and the substituents on the guanidinium moiety. Recycling experiments showed that the catalyst can be used at least three times. Furthermore, new guanidinium phosphotungstates with the PW12O403– anion were synthesized and characterized. Their catalytic performance was evaluated, and GILs as well as acetonitrile were employed as the solvent. Results were compared to those obtained with the comparable ammonium‐based catalysts [NR4]3[PW12O40] (R = C4H9, C6H13) and the analogous imidazolium‐based catalyst [BMIM]3[PW12O40] containing the 1‐butyl‐3‐methylimidazolium cation. Employing different GILs as solvents, similar results were obtained for the guanidinium and imidazolium catalysts but significantly lower epoxide yields were obtained using the ammonium catalysts. On using acetonitrile as the solvent, guanidinium‐based catalysts exhibited a better performance than the imidazolium catalyst in the case of linear and branched olefins and vice versa in the case of cyclic olefins.

SO2Capture by Guanidinium-Based Ionic Liquids: A Theoretical Study

Ionic liquids (ILs) show good performances in SO(2) separation science, e.g., SO(2) capture from high-temperature flue gas or separation from gas mixtures. In this work, the mechanism of capturing SO(2) by three guanidinium-based ILs, 1,1,3,3-tetramethylguanidinium lactate ([tmgHH][L]), 1,1,3,3-tetramethylguanidinium bis(trifluoromethylsulfonyl)imide ([tmgHH][Tf(2)N]), and 1,1,3,3-tetramethylguanidinium tetrafluoroborate ([tmgHH][BF(4)]), is investigated by using molecular dynamic simulation and ab initio calculation. The results of condensed phase molecular dynamic simulation for the mixtures of SO(2) and these three ILs indicate the similar SO(2) organization and interaction among them; SO(2) may organize around [tmgHH](+) while it favorably organizes around the anions through Lewis acid-base interaction. Gas phase ab initio calculations show that [tmgHH][L] chemically interacts with SO(2) while [tmgHH][Tf(2)N] and [tmgHH][BF(4)] do not, which is supported by the earlier FT-IR and (1)H NMR data and is also consistent with the experimental result of a much higher absorption capability of [tmgHH][L] for SO(2) than the latter two. The anion plays a key role in the chemical interaction between [tmgHH][L] and SO(2), the S atom is bonded to the N atom on -NH(2) of [tmgHH](+), and some products with aminosulfate or aminosulfinic acid fragment may be formed. This work shows that IL structures should be carefully tailored for their final application in SO(2) capture.

Novel guanidinium-based ionic liquids as stationary phases for capillary gas chromatography

The present study describes guanidinium-based ionic liquids (GBILs) as stationary phases for capillary gas chromatography (CGC) and to the best of our knowledge, no related reports are available up to now. In this study, a hexaalkylguanidinium ionic liquid (DOTMG-NTf 2) was synthesized and coated statically onto capillary columns. Selectivity of the stationary phase was evaluated by separating Grob test mixture, test mixture, alcohols mixture, and fatty acid methyl esters mixture, and thermal stability was investigated as well. The present study demonstrates that GBILs as CGC stationary phases exhibit satisfactory selectivity and thermal stability and have a great potential as new candidates for CGC stationary phases.

Guanidinium-based ionic liquids as new electrolytes for lithium battery

Two ionic liquids based on guanidinium cations and TFSA − anion were prepared, and their electrochemical stabilities were investigated. The cathodic limiting potentials of the two ILs were 0.7 V versus Li/Li +, and their electrochemical windows were 4.2 V. However, the lithium plating and striping on Ni electrode could been observed in the two IL electrolytes containing 0.3 mol kg −1 of LiTFSA without additive. And Li/LiCoO 2 cells using the two IL electrolytes without additive showed good capacity and cycle property at the current rate of 0.2 C.