Physicochemical Characterization of Ionic Liquid Binary Mixtures Containing 1-Butyl-3-methylimidazolium as the Common Cation

FCT/MEC (Portugal), through "Investigador FCT 2014" (IF/00190/2014 to A.B.P and IF/00210/2014 to J.M.M.A.),; Projects PTD C/EQU-EQU/29737/2017; PTDC/QEQFTT/32,89/2014; IF/00210/2014/CP1244/CT0003. This work was also supported by the Associate Laboratory for Green Chemistry LAQV (financed by national funds from FCT/MCTES (UID/QUI/50006/2019)) and cofinanced by the ERDF under the PT2020 Partnership Agreement (POCI-01-0145-FEDER-007265).Mixing ionic liquids (as well as mixing an inorganic salt in an ionic liquid) constitutes an easy, elegant methodology for obtaining new ionic materials. In this study, 3 ionic liquids (ILs) sharing a common cation were synthesized and mixed in 9 different proportions giving rise to 27 binary mixtures. Specifically, 1-butyl-3-methylimidazolium nitrate, [C4C1Im][NO3], 1-butyl-3-methylimidazolium chloride, [C4C1Im]Cl, and 1-butyl-3-methylimidazolium methanesulfonate, [C4C1Im][CH3SO3], were synthesized and characterized. They all share 1-butyl-3-methylimidazolium as the common archetypal cation. None of them (or any of their binary mixtures) is liquid at room temperature (T = 298.15 K), and two of them are only in the liquid state above temperatures of 343-353 K. Despite belonging to commonly used families of ILs, their handling and the study of their liquid properties (neat and mixtures) have become particularly difficult, mainly because of their tendency to solidify and their high viscosity (caused by hydrogen-bonded networks). The main goal of this work is to evaluate the thermal, dynamic, and volumetric properties of these compounds and their mixtures as well as the solid-liquid equilibria of their binary mixtures. Thermal properties, such as melting and glass-transition temperatures, were determined or calculated. Therefore, both density and viscosity have been measured and were used for the calculation of the isobaric thermal expansion coefficient, molar volumes, excess molar volumes, and viscosity deviations to linearity.authorsversionpublishe

Ionic liquids at electrified interfaces

Until recently, “room-temperature” (<100–150 °C) liquid-state electrochemistry was mostly electrochemistry of diluted electrolytes(1)–(4) where dissolved salt ions were surrounded by a considerable amount of solvent molecules. Highly concentrated liquid electrolytes were mostly considered in the narrow (albeit important) niche of high-temperature electrochemistry of molten inorganic salts(5-9) and in the even narrower niche of “first-generation” room temperature ionic liquids, RTILs (such as chloro-aluminates and alkylammonium nitrates).(10-14) The situation has changed dramatically in the 2000s after the discovery of new moisture- and temperature-stable RTILs.(15, 16) These days, the “later generation” RTILs attracted wide attention within the electrochemical community.(17-31) Indeed, RTILs, as a class of compounds, possess a unique combination of properties (high charge density, electrochemical stability, low/negligible volatility, tunable polarity, etc.) that make them very attractive substances from fundamental and application points of view.(32-38) Most importantly, they can mix with each other in “cocktails” of one’s choice to acquire the desired properties (e.g., wider temperature range of the liquid phase(39, 40)) and can serve as almost “universal” solvents.(37, 41, 42) It is worth noting here one of the advantages of RTILs as compared to their high-temperature molten salt (HTMS)(43) “sister-systems”.(44) In RTILs the dissolved molecules are not imbedded in a harsh high temperature environment which could be destructive for many classes of fragile (organic) molecules

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+][Tf2N?]), and a reactive hypergolic ionic liquid, 1-Butyl-3-Methyl-Imidazolium Dicyanamide ([Bmim+][Dca?]), are generated by vaporizing ionic liquid submicron 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+][Tf2N?]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 submicron 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

The Opposite effect of water and n-methyl-2-pyrrolidone cosolvents on the nanostructural organization of ethylammonium butanoate ionic liquid: a small- and wide-angle X-ray scattering and molecular dynamics simulations study

Two series of mixtures of ethylammoniumbutanoate (EAB, [N-0 0 0 2] [C3CO2]) in water and N-methyl-2-pyrrolidone (NMP) have been prepared at different molar fractions to assess the effect of these two polar solvents on the nanostructural order present in [N-0 0 0 2] [C3CO2]. The small and wide-angle X-ray scattering (SWAXS) pattern of the liquid in neat state shows a prepeak at Q = 0.513 angstrom(-1), which is associated with the aggregation of nonpolar alkyl chains of both cations and anions. Interestingly, the two solvents affect the nanostructure of [N-0 0 0 2] [C3CO2] differently, though both are polar. In the case of water addition to the mixture, the prepeak shifts to lower Q values, while in NMP, it moves toward higher values. Also, the principal peaks move in opposite direction in both solvents. The underlying expansion (water) or contraction (NMP) of the solutions observed by the scattering experiments is discussed in terms of molecular dynamics (MD) simulations, which are in very good agreement with the observed patterns

Complessi liquido ionico-cobalto: un\u2019interazione termocromica

Le ben note propriet\ue0 chimico-fisiche dei liquidi ionici (ILs), unite alla versatilit\ue0 strutturale, sono alla base delle loro numerose e differenti applicazioni. In questo lavoro, si presenta un\u2019interazione termocromica reversibile, sia in soluzione che in un film polimerico, tra un IL portante sul catione un residuo gluconammidico e il sale di cobalto Co(NTf2)2. I gruppi ossidrilici sul catione e l\u2019anione bromuro dell\u2019IL coordinano il Co al variare della temperatura applicata. A temperatura ambiente il complesso OH-Co risulta ottaedrico (rosa) mentre, intorno ai 60 \ub0C, la geometria diviene tetraedrica con lo ione bromuro che coordina il Co (blu). Lo studio VT UV-vis (Figura 1) ha permesso di identificare le bande relative ai complessi e il loro andamento con la temperatura, determinando anche la temperatura di switch delle geometrie. Incorporando metallo e legante in un polimero, \ue8 stato ottenuto un film polimerico avente le stesse propriet\ue0 della soluzione. Il range di temperatura del fenomeno termocromico studiato (20-90m\ub0C) \ue8 tale da rendere il sistema applicabile in device termosensibil