Solvation in aqueous binary mixtures: consequences of the hydrophobic character of the ionic liquids and the solvatochromic probes

Abstract

2012Solvation in aqueous binary mixtures:consequences of the hydrophobic character of the ionic liquids and the solvatochromic probes NEW JOURNAL OF CHEMISTRY, CAMBRIDGE, v. 36, n. 11, pp. 2353-2360, NOV, 2012 Information on the solvation in mixtures of water, W, and the ionic liquids, ILs, 1-allyl-3-R-imidazolium chlorides; R = methyl, 1-butyl, and 1-hexyl, has been obtained from the responses of the following solvatochromic probes: 2,6-dibromo-4-[(E)-2-(1-R-pyridinium-4-yl)ethenyl] phenolate, R = methyl, MePMBr 2 ; 1-octyl, OcPMBr 2 , and the corresponding quinolinium derivative, MeQMBr 2 . A model developed for solvation in binary mixtures of W and molecular solvents has been extended to the present mixtures. Our objective is to assess the relevance to solvation of hydrogen-bonding and the hydrophobic character of the IL and the solvatochromic probe. Plots of the medium empirical polarity, E T (probe) versus its composition revealed non-ideal behavior, attributed to preferential solvation by the IL and, more efficiently, by the IL-W hydrogen-bonded complex. The deviation from linearity increases as a function of increasing number of carbon atoms in the alkyl group of the IL, and is larger than that observed for solvation by W plus molecular solvents (1-propanol and 2-(1-butoxy)ethanol) that are more hydrophobic than the ILs investigated. This enhanced deviation is attributed to the more organized structure of the ILs proper, which persists in their aqueous solutions. MeQMBr 2 is more susceptible to solvent lipophilicity than OcPMBr 2 , although the former probe is less lipophilic. This enhanced susceptibility agrees with the important effect of annelation on the contributions of the quinonoid and zwitterionic limiting structures to the ground and excited states of the probe, hence on its response to both medium composition and lipophilicity of the IL.

Probing Cellulose Acetylation in Binary Mixtures of an Ionic Liquid with Dimethylsulfoxide and Sulfolane by Chemical Kinetics, Viscometry, Spectroscopy, and Molecular Dynamics Simulations

“…We explain this result by considering that cellulose is reacting as (cellOH…IL) complex, akin to alcohol‐IL complexes and water‐IL complexes; this leads to the dependence of k 3 on c (IL). This explanation is based on cellulose solubility measurements and theoretical calculations that clearly indicated the strong interactions of cellulose with IL/MS mixtures .…”

Electrochemical surface-enhanced Raman spectroscopy (E-SERS) of novel biodegradable ionic liquids

“…Spectroelectrochemical studies of the neat ILs were not possible for all of the ILs studied due to the small sample size available, and also due to the fact that some of the ILs in the series were not liquids at room temperature. While the ionic liquid dissolved in methanol may not provide the most accurate picture of the behaviour of the neat ionic liquid/metal interface, such binary solvent systems are commonly used in the application of ILs, 32,[49][50][51][52][53][54][55][56][57][58][59][60] and so an understanding of this ternary interface (IL/methanol/metal electrode) is valuable nonetheless.…”

Experimental and theoretical studies on solvation in aqueous solutions of ionic liquids carrying different side chains: the n-butyl-group versus the methoxyethyl group

“…† (xii) At any temperature, all values of IL-W/IL and IL-W/W are much larger than unity; i.e., the complex solvent is more efficient than its precursors, which is in agreement with our previous data on solvation of different probes (WB and merocyanines) in aqueous ILs. 31,67 We discuss this relative efficiency by considering the interactions involved in the solvation of the phenolate oxygen of WB. IL-W is more efficient than IL and W because it offers more possibilities for hydrogen bonding, e.g., (C5-H/ À O-WB) and (C2-H/O(H)H/ À O-WB) simultaneously.…”

“…4 This non-ideality covers both macroscopic properties, e.g., viscosity, surface tension, and conductivity, [27][28][29] and microscopic ones, e.g., solvent empirical polarity, SA, and SB. 30,31 The latter properties are determined by the use of solvatochromic dyes (hereaer designated as "probes"). [32][33][34] These are compounds whose UV-Vis spectra, absorption or emission, are particularly sensitive to a specic solvent property.…”