Are dipolar liquids ferroelectric?

VH and HV depolarized hyper-Rayleigh scattering spectra were measured for liquid solutions of dipolar CH3CN in nondipolar C2Cl4 at T=300 K. The VH spectrum contains a strong narrow peak due to a slowly relaxing longitudinal orientation mode. This peak is absent in the HV spectrum, and it disappears from the VH spectrum when the CH3CN concentration is reduced to 8%. This observation is consistent with a ferroelectric phase transition predicted to occur when rho mu0(2)=9epsilon0kT=49 D2 M.     

Applications of functionalized ionic liquids

Recent developments of the synthesis and applications of functionalized ionic liquids (including dual-functionalized ionic liquids) have been highlighted in this review. Ionic liquids are at-tracting attention as alternative solvents in green chemistry, but as more functionalized ILs are pre-pared, a greater number of applications in increasingly diverse fields are found.     

Fischer—Tropsch synthesis in ionic liquids

A comparative evaluation of the activity of different catalysts in the Fischer—Tropsch synthesis was performed. The reaction was conducted under batch conditions (autoclave) with the catalysts suspended in nonpolar and polar media, viz., n-decane or ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate. The fused Fe—K system, cobalt carbonyl, and pivalate complex [Co(Piv)_2–x OH] _n were used as catalysts. In the most cases, the use of the non-acidic ionic liquid decreases the activity of these catalytic systems. The formation of liquid hydrocarbons С₅—С₁₄ is observed only with the combination ionic liquid—Сo₂(CO)₈. When the Fe—К catalyst is modified with a cocatalyst in the form of the ionic liquid supported on the silica gel surface ([BMIM][BF₄](30%)/SiO₂), the conversion of carbon monoxide somewhat increases (by 5—7%). The ratio paraffins/olefins/iso-paraffins/aromatics in the reaction products was shown to change in a wide range.     

Are dipolar liquids ferroelectric? Simulation studies

The observation of a very sharp low frequency spike in the hyper-Rayleigh spectrum (HRS) of strongly dipolar fluids, such as acetonitrile and water, has been interpreted as reflecting a very slowly relaxing component in the transverse dipole density. This suggestion is at variance with the expectation of the dielectric theory for an isotropic fluid and has led to the speculation that the slow relaxation is associated with the reorganization of ferroelectric domains. Very large-scale molecular-dynamics simulation (approximately 28,000 molecules) have been carried out using a three-site potential model of acetonitrile. The simulated fluid shows no suggestion of strong dipole correlations and domain structure. The dipole density correlations behave as predicted by the normal dielectric theory and their spectra do not show the low-frequency feature seen in the HRS. In order to examine the characteristics of the spectra which would be seen in a ferroelectric domain, the acetontrile model was transmuted to more closely resemble a Stockmayer-type fluid with the same dipole density and a ferroelectric phase was observed. In this phase the dielectric spectra show (i) a high-frequency spectral feature due to librational motion of the molecules within a domain, and (ii) slowly-relaxing longitudinal and transverse polar modes, again at variance from the experimental HRS characteristics.     

Syntheses of CuO nanostructures in ionic liquids

A simple and efficient approach is developed to fabricate single-crystalline CuO nanostructures through an ionic liquid assisted one-step low-temperature solid-state route.Both nanoparticles(5 nm in size)and nanorods(5-10 nm in diameter and 50-100 nm in length)of monoclinic CuO were obtained. These synthesized CuO nanostructures were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),selected area electron diffraction(SAED),X-ray photoelectron spectros- copy(XPS),energy dispersive spectroscopy(EDS)and nitrogen adsorption analysis.The morpholo- gies of the nanostructures can be controlled by tuning the amount of NaOH and ionic liquids.The growth mechanism of CuO nanostructures is investigated.     

Double-layer in ionic liquids: paradigm change?

Applications of ionic liquids at electrified interfaces to energy-storage systems, electrowetting devices, or nanojunction gating media cannot proceed without a deep understanding of the structure and properties of the interfacial double layer. This article provides a detailed critique of the present work on this problem. It promotes the point of view that future considerations of ionic liquids should be based on the modern statistical mechanics of dense Coulomb systems, or density-functional theory, rather than classical electrochemical theories which hinge on a dilute-solution approximation. The article will, however, contain more questions than answers. To trigger the discussion, it starts with a simplified original result. A new analytical formula is derived to rationalize the potential dependence of double-layer capacitance at a planar metal-ionic liquid interface. The theory behind it has a mean-field character, based on the Poisson-Boltzmann lattice-gas model, with a modification to account for the finite volume occupied by ions. When the volume of liquid excluded by the ions is taken to be zero (that is, if ions are extremely sparsely packed in the liquid), the expression reduces to the nonlinear Gouy-Chapman law, the canonical result typically used to describe the potential dependence of capacitance in electrochemical double layers. If ionic volume exclusion takes more realistic values, the formula shows that capacitance-potential curves for an ionic liquid may differ dramatically from the Gouy-Chapman law. Capacitance has a maximum close to the potential of zero charge, rather than the familiar minimum. At large potenials, capacitance decreases with the square root of potential, rather than increases exponentially. The reported formula does not take into account the specific adsorption of ions, which, if present, can complicate the analysis of experimental data. Since electrochemists use to think about the capacitance data in terms of the classical Gouy-Chapman theory, which, as we know, should be good only for electrolytes of moderate concentration, the question of which result is "better" arises. Experimental data are sparse, but a quick look at them suggests that the new formula seems to be closer to reality. Opinions here could, however, split. Indeed, a comparison with Monte Carlo simulations has shown that incorporation of restricted-volume effects in the mean-field theory of electrolyte solutions may give results that are worse than the simple Gouy-Chapman theory. Generally, should the simple mean-field theory work for such highly concentrated ionic systems, where the so-called ion-correlation effects must be strong? It may not, as it does not incorporate a possibility of charge-density oscillations. Somehow, to answer this question definitely, one should do further work. This could be based on density-functional theory (and possibly not on what is referred to as local density approximation but rather "weighted density approximation"), field theory methods for the account of fluctuations in the calculation of partition function, heuristic integral equation theory extended to the nonlinear response, systematic force-field computer simulations, and, most importantly, experiments with independently determined potentials of zero charge, as discussed in the paper.     

Do supercooled liquids freeze by spinodal decomposition?

Two questions are addressed in this paper: Is it likely that spinodals occur in the freezing of one-component liquids at degrees of supercooling as moderate as T/T melt=0.6, and are the ramified solidlike structural fluctuations seen in simulations of supercooled liquids the tell-tale harbingers of spinodal decomposition? It has been suggested in several papers that in the freezing of argonlike systems, a spinodal can be expected to be encountered at T/T melt of approximately 0.6 or even at a shallower degree of supercooling. Heuristic evidence, particularly that found in molecular dynamics simulations in the system of selenium hexafluoride, a substance with properties similar in several respects to those of argon, suggests that a spinodal does not occur at supercoolings even considerably deeper than T/T melt=0.6. Reinforcing this conclusion are arguments based on nucleation kinetics in the Appendix. It has been found that many of the very thin, ramified solidlike fluctuations encountered in simulations of deeply supercooled liquids do not, in themselves, qualify as true nuclei for freezing but do, nevertheless, significantly influence the properties of the liquids. They contribute to the breakdown of the Stokes-Einstein relation universally found in supercooled liquids, liquids which have not been seen to exhibit a spinodal. Although such ramified fluctuations have been postulated to be precursors of spinodal decomposition, that role has not yet been confirmed.     

Sustainable Diels–Alder syntheses in imidazolium ionic liquids

An effective and simple protocol for the Diels–Alder reactions catalyzed and mediated by ionic liquid in conjunction with Lewis acid was studied. Diels–Alder adduct of the reaction of 1,4-benzoquinone with isoprene and 2,3-dimethyl-1,3-butadiene was obtained in good to excellent yields within the time span of 5.00–4.00 min under microwave irradiation. Due to the excellent activity of 2,3-dimethyl-1,3-butadiene as a diene, its efficiency was further analyzed by performing against four different dienophiles under various reaction conditions. The ionic liquid, 3-methyl-1-octyl-imidazolium tetrachloroaluminate mixed with Lewis acids, could be recycled and reused for consecutive cycles. The recovered ionic liquid in conjunction with Lewis acid displayed almost similar activity without any significant loss. This system is an essential upgrade and related to the reactions consuming common organic solvents at high temperatures and longer duration. Diels–Alder reactions under solventless conditions have also been investigated for the aforesaid reactions.     

Periodicity and map for discovery of new ionic liquids

1 Introduction In undertaking the researches on ionic liquids, we wished to establish periodicity and draw a “map” of ionic liquids for providing definite guidance to dis-cover, design, and choose the proper ionic liquids to meet the specific applicatio…     

Coordination of 1,10-phenanthroline and 2,2'-bipyridine to Li+ in different ionic liquids. How innocent are ionic liquids?

On the basis of (7)Li NMR measurements, we have made detailed studies on the influence of the ionic liquids [emim][NTf(2)], [emim][ClO(4)], and [emim][EtSO(4)] on the complexation of Li(+) by the bidentate N-donor ligands 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen). For each of the employed ionic liquids the NMR data implicate the formation of [Li(bipy)(2)](+) and [Li(phen)(2)](+), respectively. X-ray diffraction studies were performed to determine the coordination pattern in the solid state. In the case of [emim][ClO(4)] and [emim][EtSO(4)], crystal structures confirmed the NMR data, resulting in the complexes [Li(bipy)(2)ClO(4)] and [Li(phen)(2)EtSO(4)], respectively. On the contrary, the ionic liquid [emim][NTf(2)] generated the C(i) symmetric, dinuclear, supramolecular cluster [Li(bipy)(NTf(2))](2), where the individual Li(+) centers were found to be bridged by two [NTf(2)] anions. Density functional theory (DFT)-calculations lead to further information on the effect of stacking on the coordination geometry of the Li(+) centers.     

Preparation and characterization of amino or carboxyl-functionalized ionic liquids

New functionalized ionic liquids,1-carboxylmethyl-3-methylimimidazolium hexafluorophosphate or fluoborate and 1-ami- noethyl-3-methylimimidazolium hexafluorophosphate or fluoborate have been synthesized and investigated.The obtained amino or carboxyl-functionalized ionic liquids were all characterized by FT-IR,~1H NMR and MS(ESI)and their properties such as freezing point,viscosity,solubility,specific gravity,surface tension,and interracial tension were also determined.     

Do anions influence the polarity of protic ionic liquids?

Polarity studies in two classes of imidazolium-based protic ionic liquids (PILs) possessing [HSO(4)](-), [HCOO](-), [CH(3)COO](-) and [CH(3)CH(2)COO](-) anions were carried out using a solvatochromic method from 298.15 to 353.15 K. For 1-methylimidazolium class of PILs, E(T)(30) was found to be independent over the entire range of temperature, while E(T)(30) was noted to decrease with a rise in temperature in the case of 1-butylimidazolium class of PILs containing [CH(3)COO](-) and [CH(3)CH(2)COO](-) anions. The E(T)(30) value decreases in both the classes upon varying the anions ([HSO(4)](-), [HCOO](-), [CH(3)COO](-) and [CH(3)CH(2)COO](-)). The E(T)(30) value is controlled by hydrogen bond acceptor basicity, β, and dipolarity/polarizability, π*. The E(T)(30) value for PILs varies inversely to the strength of the coulombic interaction between ions in PILs. Strong interactions between ions lead to lower E(T)(30) values. Unlike the poor thermal effect on E(T)(30), the Kamlet-Taft parameters i.e. α, β and π* have pronounced thermal effect in the imidazolium-based PILs. Variation in the Kamlet-Taft parameters is controlled by the stabilization of ions and the degree of proton transfer from Br?nsted acid to Br?nsted base.     

Synthesis of multi-hydroxyl and sulfonyl dual-functionalized room temperature ionic liquids

Starting from the hydroxylamine (dimethyl amino ethanol, triethanolamine) and 1,3-propane sultone, a series of hydroxyl and sulfonyl dual-functionalized zwitterionic salts and corresponding acidic room temperature ionic liquids have been synthesized. The hydroxyl groups of the synthesized substances were confirmed by the 1H NMR measurement. These zwitterionic salts and ionic liquids may be used for synthesizing other functionalized ionic liquids or ionic liquid-polymer (polyelectrolyte).     

Ionic liquids in separations of azeotropic systems – A review

Efforts to make existing separation methods more efficient and eco-friendly may get a boost from the use of a relatively new class of compounds known as ionic liquids (ILs). The separation of azeotropic mixtures has conventionally been one of the most challenging tasks in industrial processes due to the fact that their separation by simple distillation is basically impossible.This paper provides a critical review of methods using ILs as azeotrope breakers. Three separation processes were addressed: liquid–liquid extraction, extractive distillation, and supported liquid membranes. We examine the azeotrope breaking potential of ILs and compare their performance to that of conventional solvents. A systematic analysis of the influence of the structure of ILs on their azeotrope breaking capacity contributes to the establishment of guidelines for selecting the most suitable ILs for the separation of specific azeotropic mixtures.     

Do organic solutes experience specific interactions with ionic liquids?

In an attempt to understand the nature of interactions between organic solutes and room temperature ionic liquids, temperature-dependent rotational relaxation of two structurally similar nondipolar solutes--2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DMDPP) and 1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP)--has been examined in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim+][PF6(-)]). Even with the ionic liquid, where the cation and the anion are strongly associated, the solute DPP experiences specific interactions, which is evident from its reorientation times that are 50%-60% longer in relation to DMDPP. It has been noticed that the reorientation times of both the solutes are faster in [bmim+][PF6(-)] than in glycerol, which is also a strongly associated solvent and whose viscosity is similar to the ionic liquid. This observation has been explained by taking into consideration the relative sizes of the solvents. By comparing the ratios of the reorientation times of DPP to DMDPP, in [bmim+][PF6(-)] and glycerol, it has been deduced that the strengths of the interaction between DPP-[bmim+][PF6(-)] and DPP-glycerol are the same.     

Brønsted acid-base ionic liquids for fuel cell electrolytes

A simple protic ionic liquid obtained from the combination of diethylmethylamine and trifluoromethanesulfonic acid exhibits the remarkable results as a medium temperature fuel cell electrolyte under non-humidifying conditions, affording a higher and stable open-circuit potential, wide liquid temperature range, and high thermal stability.     

Pressing matter: why are ionic liquids so viscous?

Room temperature ionic liquids are considered to have huge potential for practical applications such as batteries. However, their high viscosity presents a significant challenge to their use changing from niche to ubiquitous. The modelling and prediction of viscosity in ionic liquids is the subject of an ongoing debate involving two competing hypotheses: molecular and local mechanisms versus collective and long-range mechanisms. To distinguish between these two theories, we compared an ionic liquid with its uncharged, isoelectronic, isostructural molecular mimic. We measured the viscosity of the molecular mimic at high pressure to emulate the high densities in ionic liquids, which result from the Coulomb interactions in the latter. We were thus able to reveal that the relative contributions of coulombic compaction and the charge network interactions are of similar magnitude. We therefore suggest that the optimisation of the viscosity in room temperature ionic liquids must follow a dual approach.

We use an experimental approach to compare an ionic liquid with a molecular mimic, focusing on viscosities. Charge network and coulombic compaction contribute significantly to the high viscosity of ionic liquids; we discuss the implications on their design and optimisation.     

A novel family of green ionic liquids with surface activities

Ionic liquids have many unique properties as a new and remarkable class of environmental benign solvents,which promises widespread applications in industry and other areas. However,the ionic liq-uids with surface activity are rarely reported. In this work,a series of novel ionic liquids was synthe-sized by using N-methyl-2-pyrrolidone and alkyl bromide. The physical properties of this family of ionic liquids have been characterized,which shows that these compounds have ionic liquids characteristics,surface activity and biocompatibility.     

Room temperature ionic liquids and their mixtures—a review

Room temperature ionic liquids are salts that are liquid at room temperature and their use as catalysts and catalytic support has been studied extensively. They are also being considered as “green solvents” for various separation processes. Recent measurements reported on the properties of pure ionic liquids and their mixtures, including gas and liquid solubility in common organic solvents will be reviewed. While some property values are in good agreement, some show large differences. These values will be compared and reasons for the discrepancies will be conjectured. Since traditional approaches to predicting the properties of fluid liquids require extensive LLE and VLE measurements, alternative predictive methods need to be explored. The predictions of the properties of mixtures of ionic liquids using COSMOtherm, an approach based on unimolecular quantum chemical calculations of the individual molecules, will be presented.     

Are these liquids explosive? Forensic analysis of confiscated indoor fireworks

Complete forensic analysis of several confiscated liquids and gels putatively used as firework components was achieved by combining Raman, FTIR spectroscopy, and scanning electron microscopy combined with energy-dispersive spectroscopy (SEM–EDS). The chemical composition of the liquids was consistent with their use as indoor fireworks. Alcohols (methanol and isopropyl alcohol) were used to solubilise compounds producing coloured flames. Boric acid, recently introduced in the list of Substances of Very High Concern (SVHC) for the REACH Regulation of the European Union, was found in one of the samples.