Solvatochromic absorbance probe behavior within 1-butyl-3-methylimidazolium hexafluorophosphate+propylene carbonate: Preferential solvation or solvent–solvent interaction?

Probing structural patterns of ion association and solvation in mixtures of imidazolium ionic liquids with acetonitrile by means of relative1H and13C NMR chemical shifts

“…) H 2 was found to be exceptionally sensitive just as in the present study. 16,25,41,42,54,55,63,64,66 This can be related to differences in strengths of the hydrogen bonds present in ion aggregates at H 2 and H [4][5] sites for different ILs as it was noted in our recent paper. 92 A notable effect is also observed for C a H 2 and NCH 3 protons (which are adjacent to the imidazolium ring) and even for C b H 2 .…”

“…28,51,54 For some systems, however, there was no appreciable difference in chemical shift variation for the ring hydrogen atoms and the terminal methyl which resulted in roughly zero values of the relative chemical shift variations like in BmimBF 4 -H 2 O (note that there is a number of reports for this system concerning negative values of the relative chemical shift variation), 75,76 and RmimBF 4ethylene glycol. 79 There are several examples of rather peculiar behavior when H 2 and H [4][5] show opposite trends in their relative chemical shift variations. For HexmimTFSI in CDCl 3 , H 2 was found to exhibit high positive values of DDd i (x) and moderate negative values for H 4-5 , 65 similar observations were reported for EmimBF 4 in CD 2 Cl 2 , 80 while for BmimCl in DMSO the situation was inverse in signs.…”

“…are typically combined with polar aprotic solvents such as acetonitrile (AN), propylene carbonate (PC), and g-butyrolactone (g-BL). [4][5][6] Originally, dilution of ILs in molecular solvents was considered as a simple mean to reduce their high viscosity for the sake of practical handling. However, not only does it increase the fluidity, but modifies the overall pattern of intermolecular and interionic interactions and the related properties, e.g., electrical conductivity, 7-10 polarity, 5,11,12 diffusivity.…”

“…[4][5][6] Originally, dilution of ILs in molecular solvents was considered as a simple mean to reduce their high viscosity for the sake of practical handling. However, not only does it increase the fluidity, but modifies the overall pattern of intermolecular and interionic interactions and the related properties, e.g., electrical conductivity, 7-10 polarity, 5,11,12 diffusivity. [13][14][15][16] In terms of efficient practical use and development of novel IL-molecular solvent systems, the key fundamental issue is to establish a comprehensive microscopic picture on the structure and dynamics in such systems as a function of mixture composition and nature of the constituents.…”

Task specific ionic liquids as polarity shifting additives of common organic solvents

“…It was reported that the addition of small quantities of [BMIM][PF 6 ] to propylene carbonate results in a dramatic increase in polarity. 7 When using minute quantities of [BMIM][Cl] as co-solvent in acetonitrile for the extraction of mixed tocopherols dissolved in hexane it was found that the selectivity of d-tocopherol to a-tocopherol was four times larger than when using pure acetonitrile and the distribution coefficients were at least eighteen times larger than when using pure [BMIM][Cl]. 8 Mellein and co-workers tested the inverse case, i.e., the addition of small quantities of organic solvents to ionic liquids and found that the polarity of ionic liquids (ILs) is largely unaffected by the organic co-solvent.…”