The electrochemical and physical properties of a class of 1-n-alkyl-3-methylimidazolium (C n mim) bis(perfuoroalkylsulfonyl)imide room-temperature ionic liquids (RTILs) is reported. By varying the chain length on the cation (n = 6, 8, and 10) and the perfluorinated carbon chains of the imide anions, -CF 3 (BMSI) to -CF 2 CF 3 (BETI), the effect on water content, viscosity, conductivity, and potential window has been examined. The water content of the RTILs, both ambient and water-equilibrated, varies linearly with the imidazolium alkyl chain length. The viscosities of the water-equilibrated BMSI- and BETI-based RTILs were accurately calculated using a linear combination of the viscosity of water and the ambient RTILs. The conductivities for this series ranges from 2.9 mS/cm (C 6 mimBMSI) to 0.92 mS/cm (C 10 mimBETI) and were accurately estimated based on the viscosity, density, and molecular weight. The potential windows of the ambient RTILs are 4.3 and 4.9 V for the BMSI and BETI salts, respectively. The window is reduced to 3.9 and 4.3 V upon equilibration with water. The reversible electrochemistry of ferrocene (ΔE P = 70 mV) and decamethylferrocene (ΔE p = 63 mV) has been measured in water-equilibrated imide-based RTILs with as much as 23 mol% H 2 O.

https://iopscience.iop.org/article/10.1149/1.1751197/pdf

1-Alkyl-3-methylimidazolium Bis(perfluoroalkylsulfonyl)imide Water-Immiscible Ionic Liquids The Effect of Water on Electrochemical and Physical Properties

The water solubility of salts is ordinarily dictated by lattice energy and ion solvation. However, in the case of low melting salts also known as ionic liquids, lattice energy is immaterial and differences in hydrophobicity largely account for differences in their water solubility. In this contribution, the activity coefficients of ionic liquids in water are split into cation and anion contributions by regression against cation hydrophobicity parameters that are experimentally determined by reversed phase liquid chromatography. In this way, anion hydrophobicity parameters are derived, as well as an equation to estimate water solubilities for cation-anion combinations for which the water solubility has not been measured. Thus, a new pathway to the quantification of aqueous ion solvation is shown, making use of the relative weakness of interactions between ionic liquid ions as compared to their hydrophobicities.

/pdf/explaining-ionic-liquid-water-solubility-in-terms-of-cation-3retjgl3q5.pdf

Explaining Ionic Liquid Water Solubility in Terms of Cation and Anion Hydrophobicity

Water sorption by anhydrous ionic liquids

The potential of room‐temperature ionic liquids for use in chemical separations was assessed, particularly for liquid–liquid extraction. The solubility, surface tension, and electrical conductivity of a range of imidazolium‐based ionic liquids in aqueous solution were measured at room temperature and atmospheric pressure as functions of ionic‐liquid, sodium chloride, and potassium–chloride concentrations. Hydrophobic ionic liquids were studied, including 1‐C n ‐3‐methylimidazolium cations, C n mim+, with alkyl substitutions of varying chain length, where C n =C2 (ethyl), C4 (butyl), C6 (hexyl), and C8 (octyl), in combination with bis(trifluoromethanesulfonyl)imide, NTf2 −, and bis(perfluoroethanesulfonyl)imide, BETI−, anions. Hydrophilic compounds were also studied, with bromide anions and C n mim+ and 1‐C n ‐2, 3‐methylimidazolium, C n bmim+, cations, where C n =C12, C14 and C16 are solids at room temperature, and C n =C8, C9, and C10 are liquids.

Room‐Temperature Ionic Liquids in Liquid–Liquid Extraction: Effects of Solubility in Aqueous Solutions on Surface Properties

Attaching molecular catalysts to metal and semiconductor electrodes is a promising approach to developing new catalytic electrodes with combined advantages of molecular and heterogeneous catalysts. However, the effect of the interfacial electric field on the stability, activity, and selectivity of the catalysts is often poorly understood due to the complexity of interfaces. In this work, we examine the strength of the interfacial field at the binding site of CO2 reduction catalysts including Re(S-2,2′-bipyridine)(CO)3Cl and Mn(S-2,2′-bipyridine)(CO)3Br immobilized on Au electrodes. The vibrational spectra are probed by sum frequency generation spectroscopy (SFG), showing pronounced potential-dependent frequency shifts of the carbonyl stretching modes. Calculations of SFG spectra and Stark tuning rates based on density functional theory allow for direct interpretation of the configurations of the catalysts bound to the surfaces and the influence of the interfacial electric field. We find that electrocataly...

CO 2 Reduction Catalysts on Gold Electrode Surfaces Influenced by Large Electric Fields

Phase-boundary potential across the nonpolarized interface between the room-temperature molten salt and water

Determination of the potential of zero charge of Au(111) electrodes modified with thiol self-assembled monolayers using a potential-controlled sessile drop method

Yasunobu Iwami

Papers

Phase-boundary potential across the nonpolarized interface between the room-temperature molten salt and water

Determination of the potential of zero charge of Au(111) electrodes modified with thiol self-assembled monolayers using a potential-controlled sessile drop method