微波辅助合成有机膦功能化离子液体及对稀土离子的萃取

用微波辐射法,合成了5个含有机膦氧基团的离子液体：1-丙基-3-(3-二苯基氧膦基)丙基咪唑双(三氟甲基磺酰基)亚胺盐([PImC3P(O)Ph2][Tf2N])、1-己基-3-(3-二苯基氧膦基)丙基咪唑双(三氟甲基磺酰基)亚胺盐([HImC3P(O)Ph2][Tf2N])、1-丙基-3-(3-苯基乙氧基氧膦基)丙基咪唑双(三氟甲基磺酰基)亚胺盐([PImC3P(O)Ph(OEt)][Tf2N])、1-己基-3-(3-苯基乙氧基氧膦基)丙基咪唑双(三氟甲基磺酰基)亚胺盐([HImC3P(O)Ph(OEt)][Tf2N])和(3-苯基乙氧基氧膦基)丙基三乙胺双(三氟甲基磺酰基)亚胺盐([TENC3P(O)Ph(OEt)][Tf2N])。 用31P NMR、1H NMR、13C NMR、MS及FT-IR对产物结构进行了表征。 研究了这类离子液体对稀土Nd(III)的萃取性能。 结果表明,这类功能化离子液体可作为单一组分萃取稀土而无需加入有机稀释剂,离子液体结构对萃取效率影响很大,相同条件下季铵盐型结构的离子液体[TENC3P(O)Ph(OEt)][Tf2N]对稀土Nd(Ⅲ)的萃取效率最高。 稀土溶液pH值对萃取效率影响显著,近中性条件下(pH=6.63),对稀土Nd(Ⅲ)的萃取率最高。 用pH=1.00的盐酸溶液可以较好的从离子液体相反萃Nd(Ⅲ),反萃率可达94%。     

A comparison of the ultraslow relaxation processes at the ionic liquid|water interface for three hydrophobic ionic liquids

The ultraslow relaxation, on the order of a few seconds or longer, of the structure of the electrical double layer in response to the change in the phase-boundary potential across the ionic liquid (IL)|water(W) interface, which was recently reported for trioctylmethylammonium bis(nonafluorobutanesulfonyl)amide, has been confirmed in two new hydrophobic ionic liquids, trihexyltetradecylphosphonium bis(nonafluorobutanesulfonyl)amide and trihexyltetradecylphosphonium tetrakis(pentafluorophenyl)borate. A comparison of the degree of the hysteresis in electrocapillary curves for these ILs with those for trioctylmethylammonium bis(nonafluorobutanesulfonyl)amide demonstrates that the degree of the hysteresis is not correlated with the viscosity of these ILs. The ultraslow relaxation of the electrical double layer seems to be a general feature of ILs at electrified interfaces.     

Thermodynamics of complexation of cesium ions with dibenzo-18-crown-6 in hydrophobic ionic liquids

The stability constants of the [Cs(DB18C6)]⁺ complex (DB18C6 is dibenzo-18-crown-6, L) in hydrophobic ionic liquids (room-temperature ionic liquids, RTIL) trioctylmethylammonium salicylate ([TOMA][Sal]), tetrahexylammnoium dihexylsulfosuccinate ([THA][DHSS]), and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([BMIM][N(Tf)₂], as well as of the [Cs(18C6)₂]⁺ complex in [BMIM][N(Tf)₂], were measured by 133Cs NMR in the temperature range 27–57°C. The changes in the enthalpy and entropy of complex formation were determined. A linear correlation was revealed between logK ₁ and the extraction factor logD _Cs^DB18C6 for the cesium extraction from an aqueous solution into the RTIL.     

On the electrodeposition of titanium in ionic liquids

The ability to electrodeposit titanium at low temperatures would be an important breakthrough for making corrosion resistant layers on a variety of technically important materials. Ionic liquids have often been considered as suitable solvents for the electrodeposition of titanium. In the present paper we have extensively investigated whether titanium can be electrodeposited from its halides (TiCl(4), TiF(4), TiI(4)) in different ionic liquids, namely1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIm]Tf(2)N), 1-butyl-1-methylpyrrolidinium bis(trifluoromethyl-sulfonyl)amide ([BMP]Tf(2)N), and trihexyltetradecyl-phosphonium bis(trifluoromethylsulfonyl)amide ([P(14,6,6,6)]Tf(2)N). Cyclic voltammetry and EQCM measurements show that, instead of elemental Ti, only non-stoichiometric halides are formed, for example with average stoichiometries of TiCl(0.2), TiCl(0.5) and TiCl(1.1). In situ STM measurements show that-in the best case-an ultrathin layer of Ti or TiCl(x) with thickness below 1 nm can be obtained. In addition, results from both electrochemical and chemical reduction experiments of TiCl(4) in a number of these ionic liquids support the formation of insoluble titanium cation-chloride complex species often involving the solvent. Solubility studies suggest that TiCl(3) and, particularly, TiCl(2) have very limited solubility in these Tf(2)N based ionic liquids. Therefore it does not appear possible to reduce Ti(4+) completely to the metal in the presence of chloride. Successful deposition processing for titanium in ionic liquids will require different maybe tailor-made titanium precursors that avoid these problems.     

Soft ionization of thermally evaporated hypergolic ionic liquid aerosols

Isolated ion pairs of a conventional ionic liquid, 1-Ethyl-3-Methyl-Imidazolium Bis(trifluoromethylsulfonyl)imide ([Emim(+)][Tf(2)N(-)]), and a reactive hypergolic ionic liquid, 1-Butyl-3-Methyl-Imidazolium Dicyanamide ([Bmim(+)][Dca(-)]), are generated by vaporizing ionic liquid submicrometer aerosol particles for the first time; the vaporized species are investigated by dissociative ionization with tunable vacuum ultraviolet (VUV) light, exhibiting clear intact cations, Emim(+) and Bmim(+), presumably originating from intact ion pairs. Mass spectra of ion pair vapor from an effusive source of the hypergolic ionic liquid show substantial reactive decomposition due to the internal energy of the molecules emanating from the source. Photoionization efficiency curves in the near threshold ionization region of isolated ion pairs of [Emim(+)][Tf(2)N(-)] ionic liquid vapor are compared for an aerosol source and an effusive source, revealing changes in the appearance energy due to the amount of internal energy in the ion pairs. The aerosol source has a shift to higher threshold energy (～0.3 eV), attributed to reduced internal energy of the isolated ion pairs. The method of ionic liquid submicrometer aerosol particle vaporization, for reactive ionic liquids such as hypergolic species, is a convenient, thermally "cooler" source of isolated intact ion pairs in the gas phase compared to effusive sources.     

Separation of benzene and hexane by solvent extraction with 1-alkyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide ionic liquids: effect of the alkyl-substituent length

The influence of the alkyl-substituent chain in 1-alkyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide ionic liquids ([C(n)mim][NTf(2)], where n is the length of a linear alkyl chain) as solvents for the separation of benzene and hexane by liquid extraction was investigated. The liquid-liquid equilibrium (LLE) at 25 degrees C for the ternary systems ([C(n)mim][NTf(2)] + hexane + benzene), with n taking the values 4, 8, 10, and 12, were determined. These data were analyzed and compared to those previously reported for the system ([C(2)mim][NTf(2)] + hexane + benzene). The results show that short alkyl chains on the imidazolium cation of the ionic liquid lead to a better extractive separation of benzene and hexane, and reveal the influence of the relative degree of ordering in the ionic liquids on the extraction parameters.     

Electrodeposition of Al in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquids: in situ STM and EQCM studies

In the present paper, the electrodeposition of Al on flame-annealed Au(111) and polycrystalline Au substrates in two air- and water-stable ionic liquids namely, 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide, [Py(1,4)]Tf(2)N, and 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)amide, [EMIm]Tf(2)N, has been investigated by in situ scanning tunneling microscopy (STM), electrochemical quartz crystal microbalance (EQCM), and cyclic voltammetry. The cyclic voltammogram of aluminum deposition and stripping on Au(111) in the upper phase of the biphasic mixture of AlCl(3)/[EMIm]Tf(2)N at room temperature (25 degrees C) shows that the electrodeposition process is completely reversible as also evidenced by in situ STM and EQCM studies. Additionally, a cathodic peak at an electrode potential of about 0.55 V vs Al/Al(III) is correlated to the aluminum UPD process that was evidenced by in situ STM. A surface alloying of Al with Au at the early stage of deposition occurs. It has been found that the Au(111) surface is subject to a restructuring/reconstruction in the upper phase of the biphasic mixture of AlCl(3)/[Py(1,4)]Tf(2)N at room temperature (25 degrees C) and that the deposition is not fully reversible. Furthermore, the underpotential deposition of Al in [Py(1,4)]Tf(2)N is not as clear as in [EMIm]Tf(2)N. The frequency shift in the EQCM experiments in [Py(1,4)]Tf(2)N shows a surprising result as an increase in frequency and a decrease in damping with bulk aluminum deposition at potentials more negative than -1.8 V was observed at room temperature. However, at 100 degrees C there is a frequency decrease with ongoing Al deposition. At -2.0 V vs Al/Al(III), a bulk aluminum deposition sets in.     

Electrodeposition of Ge, Si and Si x Ge 1-x from an air- and water-stable ionic liquid

The electrodeposition of Ge, Si and, for the first time, of Si(x)Ge(1-x) from the air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py(1,4)]Tf(2)N) containing GeCl(4) and/or SiCl(4) as precursors is investigated by cyclic voltammetry and high-resolution scanning electron microscopy. GeCl(2) in [Py(1,4)]Tf(2)N is electrochemically prepared in a two-compartment cell to be used as Ge precursor instead of GeCl(4) in order to avoid the chemical attack of Ge(iv) on deposited Ge. Silicon, germanium and Si(x)Ge(1-x) can be deposited reproducibly and easily in this ionic liquid. Interestingly, the Si(x)Ge(1-x) deposit showed a strong colour change (from red to blue) at room temperature during electrodeposition, which is likely to be due to a quantum size effect. The observed colours are indicative of band gaps between at least 1.5 and 3.2 eV. The potential of ionic liquids in Si(x)Ge(1-x) electrodeposition is demonstrated.     

Non-classical diffusion in ionic liquids

In this study the diffusion coefficient of neutral and cationic ferrocenyl-derivatives have been characterised in a range of 1-alkyl-3-methylimidazolium ionic liquids of the general form [C(n)C(1)Im](+)[X](-). The electrochemistry of ferrocene, 1-ferrocenylmethylimidazole (FcC(1)Im), 1-ferrocenylmethylimidazolium bis(trifluoromethanesulfonyl)imide ([FcC(1)C(1)Im][Tf(2)N]) and N,N,N,N-trimethylferrocenyl-methylammonium bis(trifluoromethanesulfonyl)imide ([FcC(1)NMe(3)][Tf(2)N]), in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C(2)C(1)Im][Tf(2)N]) was investigated. It was shown that the diffusion coefficients of each were not significantly affected by the presence and location of a positive charge on the ferrocenyl-derivative, suggesting that coulombic solvent-solute interactions did not hinder motion of these species in ionic liquids. The diffusion coefficients for [FcC(1)C(1)Im][Tf(2)N] in five [C(n)C(1)Im][X] ionic liquids were determined as a function of temperature and the data shown to disobey the Stokes-Einstein equation. This observation is consistent with the fact that ionic liquids are glass formers, systems in which non-Stokesian behaviour is well documented. Measured diffusion coefficient data was used to determine correlation length in the ionic liquid and was found to correlate with the average size of holes, or voids, within the ionic liquid. This interpretation suggests that a model by which a migrating species can jump between voids or holes within the liquid is highly appropriate and is consistent with the observed behaviour measured across a range of temperatures.     

Deviations from ideality in mixtures of two ionic liquids containing a common ion

Excess molar volumes of six binary mixtures composed of two ionic liquids of the 1-methyl-3-alkyl-imidazolium bis(trifluoromethylsulfonyl)amide family -- ([C(m)()mim] + [C(n)()mim])[NTf(2)] with n and m ranging from 2 to 10 -- were measured for several compositions at 298 and 333 K. Similarly, three other binary systems containing [C(4)mim](+) (1-methyl-3-butylimidazolium) as a common cation have been studied: [C(4)mim]([NTf(2)] + [PF(6)]), [C(4)mim]([NTf(2)] + [BF(4)]) and [C(4)mim]([BF(4)] + [PF(6)]). Thus, the mixing process of two distinct ions of equal sign embedded in a constant field network of a given counterion was analyzed. All systems exhibit small, positive V(E) values of the order of a few tenths of cm(3) mol(-1), which are essentially temperature and pressure independent. The results show additive trends, for instance, the V(E) values become larger as the difference between the alkyl chain lengths of the two cations increases. The Flory theory of mixtures provides a useful, semiquantitative correlation between the excess volumes and excess enthalpies in these systems, allowing for comparison with analogous results obtained within the linear primary alcohols.     

Kinetics of ion transfer at the ionic liquid/water nanointerface

Ion transfer (IT) processes in ionic liquids (ILs) are essential for their applications in electrochemical systems and chemical separations. In this Article, the first measurements of IT kinetics at the IL/water interface are reported. Steady-state voltammetry was performed at the nanometer-sized polarizable interface between water and ionic liquid, [THTDP(+)][C(4)C(4)N(-)], immiscible with it that was formed at the tip of a nanopipet. Kinetic measurements at such interfaces are extremely challenging because of slow mass-transfer rates in IL, which is ～700 times more viscous than water. The recently developed new mode of nanopipet voltammetry, common ion voltammetry, was used to overcome technical difficulties and ensure the reliability of the extracted kinetic parameters of IT. The results suggest that the rate of interfacial IT depends strongly on solution viscosity. Voltammetric responses of nanopipets of different radii were analyzed to evaluate the effect of the electrical double layer at the liquid/liquid interface on IT kinetics. The possibility of the influence of the charged pipet wall on ion transport was investigated by comparing currents produced by cationic and anionic species. Possible effects of relaxation phenomena at the IL/water interface on IT voltammograms have also been explored.     

Growth of sputter-deposited gold nanoparticles in ionic liquids

The growth of gold nanoparticles (NPs) synthesized by sputter deposition on an ionic liquid surface is studied in situ in the bulk phase of the ionic liquids (ILs) 1-butyl-3-methylimidazolium dicyanamide [C(1)C(4)Im][N(CN)(2)], 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide [C(1)C(4)Im][Tf(2)N], 1-butyl-3-methylimidazolium tetrafluoroborate [C(1)C(4)Im][BF(4)], 1-butyl-3-methylimidazolium hexafluorophosphate [C(1)C(4)Im][PF(6)] and 1-butyl-3-methylimidazolium triflate [C(1)C(4)Im][TfO]. It is found that primary nanoparticles with a diameter smaller than 2.5 nm are present in the sample immediately after sputtering. Growth of these primary particles proceeds after the end of the sputtering process and stops when the nanoparticles reach a certain size. Depending on the viscosity of the ionic liquid this growth process can proceed several hours to several days. The growth speed is fastest for the least viscous ionic liquid and follows the trend [C(1)C(4)Im][N(CN)(2)] > [C(1)C(4)Im][Tf(2)N] > [C(1)C(4)Im][TfO] > [C(1)C(4)Im][BF(4)] > [C(1)C(4)Im][PF(6)]. It is also found that a higher concentration of sputtered gold results in faster growth of the gold nanoparticles. A discussion on the growth mechanism of sputtered gold NPs is included.     

Nanostructural organization and anion effects on the temperature dependence of the optical Kerr effect spectra of ionic liquids

The intermolecular spectra of three imidazolium ionic liquids were studied as a function of temperature by the use of optical heterodyne-detected Raman-induced Kerr effect spectroscopy. The ionic liquids comprise the 1,3-pentylmethylimidazolium cation ([C(5)mim]+), and the anions, bromide (Br-), hexafluorophosphate (PF(6)-), and bis(trifluoromethanesulfonyl)imide (NTf(2)-). Whereas the optical Kerr effect (OKE) spectrum of [C(5)mim][NTf(2)] is temperature-dependent, the OKE spectra of [C(5)mim]Br and [C(5)mim][PF6] are temperature-independent. These results are surprising in light of the fact that the bulk densities of these room temperature ionic liquids (RTILs) are temperature-dependent. The temperature independence of the OKE spectra and the temperature dependence of the bulk density in [C(5)mim]Br and [C(5)mim][PF(6)] suggest that there are inhomogeneities in the densities of these liquids. The existence of density inhomogeneities is consistent with recent molecular dynamics simulations that show RTILs to be nanostructurally organized with nonpolar regions arising from clustering of the alkyl chains and ionic networks arising from charge ordering of the anions and imidazolium rings of the cations. Differences in the temperature dependences of the OKE spectra are rationalized on the basis of the degree of charge ordering in the polar regions of the RTILs.     

Measurement of SO2 solubility in ionic liquids

Measurements of the solubility of sulfur dioxide (SO(2)) in the ionic liquids 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf(2)N]) and 1-n-hexyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide ([hmpy][Tf(2)N]) at temperatures from 25 to 60 degrees C and pressures up to 4 bar indicate that large amounts (up to 85 mol %) of SO(2) dissolve in ionic liquids by simple physical absorption.     

Comparison of dansylated aminopropyl controlled pore glass solvated by molecular and ionic liquids

We compare how (i) four ionic liquids (ILs) (1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][Tf2N]), 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C4mpy][Tf2N]), and trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide ([P(C6)3C14][Tf2N])) and (ii) two conventional molecular liquids (methanol and 1-octanol) solvate/wet luminescent organic moieties that are covalently attached to the surface of silica controlled pore glass (CPG). A series of aminopropyl CPG particles that have been covalently tagged with the solvatochromic fluorescent probe group dansyl were used in this study. The results demonstrate that ILs solvate/wet the silica surface differently in comparison to molecular liquids (MLs). Specifically, when comparing ILs and MLs that appear to solvate the free probe, dansylpropylsulfonamide (DPSA), equally in solution, we find that ILs do not solvate/wet the silica surfaces as well as the corresponding MLs. The cation component in these ILs is the significant factor in how the ILs solvate/wet silica surfaces. Solvation/wetting of surface-bound species at a silica surface depends on the cation size. Chlorosilane end-capping of the surface silanol and amine residues attenuates the cation's affects.     

Influence of ionic liquids bearing functional groups in dye-sensitized solar cells

Ionic liquids containing the nitrile and vinyl functional groups attached to imidazolium cations combined with various anions, e.g., iodide, bis[(trifluoromethyl)sulfonyl]imide ([TFSI]-), or dicyanamide ([N(CN)2]-), have been prepared and characterized. These ionic liquids have been successfully used as electrolytes for dye-sensitized solar cells based on nanocrystalline TiO2 with the amphiphilic ruthenium sensitizer [ruthenium (4,4'-dicarboxylic acid-2,2'-bipyridine)(4,4'-bis(p-hexyloxystyryl)-2,2'-bipyridine)][NCS]2 (coded K-19). The iodide salt was used in 3-methoxypropionitrile-based electrolytes, and the performances of both types of devices were evaluated on the basis of their photocurrent density-voltage characteristics and dark current measurements, demonstrating that the functional groups do not exert a detrimental effect on the performance. The solid-state structure of the nitrile-functionalized salt [C1C3CN(im)]I has also been established by single-crystal X-ray diffraction, revealing extensive hydrogen bonding between the cation protons and the iodide.     

Ionic liquids of bis(alkylethylenediamine)silver(I) salts and the formation of silver(0) nanoparticles from the ionic liquid system

We have prepared novel ionic liquids of bis(N-2-ethylhexylethylenediamine)silver(I) nitrate ([Ag(eth-hex-en)(2)]NO(3) and bis(N-hexylethylenediamine)silver(I) hexafluorophosphate ([Ag(hex-en)(2)]PF(6)), which have transition points at -54 and -6 degrees C, respectively. Below these transition temperatures, both the silver complexes assume amorphous states, in which the extent of the vitrification is larger for the eth-hex-en complex than for the hex-en complex. The diffusion coefficients of both the complex cations, measured between 30 (or 35) and 70 degrees C, are largely dependent on temperature; the dependence is particularly large in the case of the eth-hex-en complex cation below 40 degrees C. Small-angle X-ray scattering studies showed that the bilayer structure of the metal complex is formed in the liquid state for both the silver complexes. A direct observation of the yellowish [Ag(eth-hex-en)(2)]NO(3) liquid by transmission electron microscopy (TEM) indicates the presence of nanostructures, as a microemulsion, of less than 5 nm. Such structures were not clearly observed in the [Ag(hex-en)(2)]PF(6) liquid. Although the [Ag(eth-hex-en)(2)]NO(3) liquid is sparingly soluble in bulk water, it readily incorporates a small amount of water up to [water]/[metal complex] = 7:1. Homogeneous and uniformly sized silver(0) nanoparticles in water were created by the reduction of the [Ag(eth-hex-en)(2)]NO(3) liquid with aqueous NaBH(4), whereas silver(0) nanoparticles were not formed from the [Ag(hex-en)(2)]PF(6) liquid in the same way.     

Relative volatilities of ionic liquids by vacuum distillation of mixtures

The relative volatilities of a variety of common ionic liquids have been determined for the first time. Equimolar mixtures of ionic liquids were vacuum-distilled in a glass sublimation apparatus at approximately 473 K. The composition of the initial distillate, determined by NMR spectroscopy, was used to establish the relative volatility of each ionic liquid in the mixture. The effect of alkyl chain length was studied by distilling mixtures of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, or mixtures of N-alkyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids, with different alkyl chain lengths. For both classes of salts, the volatility is highest when the alkyl side chain is a butyl group. The effect of cation structure on volatility has been determined by distilling mixtures containing different types of cations. Generally speaking, ionic liquids based on imidazolium and pyridinium cations are more volatile than ionic liquids based on ammonium and pyrrolidinium cations, regardless of the types of counterions present. Similarly, ionic liquids based on the anions [(C2F5SO2)2N](-), [(C4F9SO2)(CF3SO2)N](-) , and [(CF3SO2)2N](-) are more volatile than ionic liquids based on [(CF3SO2)3C](-) and [CF3SO3](-), and are much more volatile than ionic liquids based on [PF6](-).     

Heterogeneous solute dynamics in room temperature ionic liquids

The excitation wavelength dependence of the emission kinetics of several solutes is used to demonstrate the presence of dynamic heterogeneity in two representative room temperature ionic liquids, dimethyl-isopropyl-propyl-ammonium bis(trifluoromethylsulfonyl)imide [N(ip311)(+)][Tf(2)N(-)] and N-propyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [Pr(31)(+)][Tf(2)N(-)]. The solute kinetics examined here include rotation and solvation of coumarin 153, isomerization of two malononitriles, and intramolecular charge transfer in crystal violet lactone. The rates of most of these processes vary significantly with excitation wavelength, especially for excitation on the red edges of the solute absorption bands, indicating that energetically selected subpopulations relax at distinct rates. The results presented here suggest more generally that dynamical processes taking place on the subnanosecond time scale in typical ionic liquids near room temperature are likely to be heterogeneous in character.