Liquid–Liquid Equilibrium of Cholinium-Derived Bistriflimide Ionic Liquids with Water and Octanol

Ionic Liquids and Water: Hydrophobicity vs. Hydrophilicity

Many chemical processes rely extensively on organic solvents posing safety and environmental concerns. For a successful transfer of some of those chemical processes and reactions to aqueous media, agents acting as solubilizers, or phase-modifiers, are of central importance. In the present work, the structure of aqueous solutions of several ionic liquid systems capable of forming multiple solubilizing environments were modeled by molecular dynamics simulations. The effect of small aliphatic chains on solutions of hydrophobic 1-alkyl-3-methylimidazolium bis(trifluoromethyl)sulfonylimide ionic liquids (with alkyl = propyl [C₃C₁im][NTf₂], butyl [C₄C₁im][NTf₂] and isobutyl [iC₄C₁im][NTf₂]) are covered first. Next, we focus on the interactions of sulphonate- and carboxylate-based anions with different hydrogenated and perfluorinated alkyl side chains in solutions of [C₂C₁im][C_nF_2n+1SO₃], [C₂C₁im][C_nH_2n+1SO₃], [C₂C₁im][CF₃CO₂] and [C₂C₁im][CH₃CO₂] (n = 1, 4, 8). The last system considered is an ionic liquid completely miscible with water that combines the cation N-methyl-N,N,N-tris(2-hydroxyethyl)ammonium [N_{1 2OH 2OH 2OH}]⁺, with high hydrogen-bonding capability, and the hydrophobic anion [NTf₂]^-. The interplay between short- and long-range interactions, clustering of alkyl and perfluoroalkyl tails, and hydrogen bonding enables a wealth of possibilities in tailoring an ionic liquid solution according to the needs.

Designing the ammonium cation to achieve a higher hydrophilicity of bistriflimide-based ionic liquids

Development of water soluble bistriflimide-based ionic liquids and molecular dynamics simulations to unveil the underlying molecular details.

On the coordination of Zn2+ ion in Tf2N− based ionic liquids: structural and dynamic properties depending on the nature of the organic cation

The Zn²⁺ coordination structure changes when the Zn(Tf₂N)₂ salt is dissolved in ionic liquids resulting in more favorable interactions among solvent cations and anions.

Physicochemical properties of novel cholinium ionic liquids for the recovery of silver from nitrate media

Linear and ramified cholinium based ionic liquids have been synthesized and their physicochemical properties have been investigated by ¹H NMR, ¹³C NMR, ATR-FTIR and ESI-MS as well as their extraction properties towards Ag(i), Cu(ii) and Fe(iii).

Spectroscopic evidence of ‘jumping and pecking’ of cholinium and H-bond enhanced cation–cation interaction in ionic liquids

Spectroscopic evidence for cation–cation interaction in ionic liquids. The repulsive electrostatic interaction is overcome by hydrogen bonding between ions of like charge.

Spontaneous emulsification in ionic liquid/water systems and its use for templating of solids

We report on the spontaneous formation of nano-sized ionic liquid/water (IL/W) emulsions in a simple system solely composed of an IL and aqueous solution of an inorganic salt. The IL ions play a dual role, that of both a surfactant and the dispersed phase. No extra surfactant is needed to promote emulsification. Droplets generation at the IL/W interface is captured by nanoparticulate and porous films that imprint the morphology of this unstable interface. The emulsion droplets are employed to create core-shell microcrystals with potential functionality.

The complex structure of ionic liquids at an atomistic level: from “red-and-greens” to charge templates

In this article, we discuss how the relation between interactions and structure in ionic liquids (ILs) can be probed at a molecular level using ab initio and molecular dynamics (MD) methodologies. The first part of the discussion will focus on the unique and complex properties of ILs as pure substances including the existence of an extended and flexible polar network and the possibility of a second nanosegregated subphase containing the nonpolar residues of the molecular ions that constitute some ILs. The discussion will then be extended to IL plus molecular species mixtures/solutions. In this context the concept of ILs as charge templates for the electronic make-up of the molecular species will be analyzed at length. Finally, that concept will be extended to ILs adsorbed over solid substrates.

Shifts in the temperature of maximum density (TMD) of ionic liquid aqueous solutions

This work investigates for the first time shifts in the temperature of maximum density (TMD) of water caused by ionic liquid solutes. A vast amount of high-precision volumetric data--more than 6000 equilibrated (static) high-precision density determination corresponding to ∼90 distinct ionic liquid aqueous solutions of 28 different types of ionic liquid--allowed us to analyze the TMD shifts for different homologous series or similar sets of ionic solutes and explain the overall effects in terms of hydrophobic, electrostatic and hydrogen-bonding contributions. The differences between the observed TMD shifts in the -2 < t/°C < 4 range and salting-in or salting-out effects produced by the same type of ions in aqueous solutions at higher temperatures are discussed taking into account the different types of possible solute-water interactions that can modify the structure of the aqueous phase. The results also reveal different insights concerning the nature of the ions that constitute typical ionic liquids and are consistent with previous results that established hydrophobic and hydrophilic scales for ionic liquid ions based on their specific interactions with water and other probe molecules.

Probing ionic liquid aqueous solutions using temperature of maximum density isotope effects

This work is a new development of an extensive research program that is investigating for the first time shifts in the temperature of maximum density (TMD) of aqueous solutions caused by ionic liquid solutes. In the present case we have compared the shifts caused by three ionic liquid solutes with a common cation—1-ethyl-3-methylimidazolium coupled with acetate, ethylsulfate and tetracyanoborate anions—in normal and deuterated water solutions. The observed differences are discussed in terms of the nature of the corresponding anion-water interactions.