Investigation of Surface Properties and Solubility of 1-Vinyl-3-alkyl/Esterimidazolium Halide Ionic Liquids by Density Functional Methods

Abstract

A series of 1-vinyl-3-alkylimidazolium halide ([VRIM]X) and 1-vinyl-3-esterimidazolium chloride ([VEIM]-Cl) ionic liquids, a functional material with unsaturated bonds, were synthesized by using microwave-assisted synthesis method. The structures were characterized by 1 H NMR. Through Gaussian09/B3PW91/6-311G (2d,p) density functional methods, the interaction energies of ion pairs of [VRIM]X and [VEIM]Cl were obtained. The relationships between the surface tensions and temperature (293.15 to 333.15) K, molecular structure, and the interaction energies of ion pairs, etc. along with the relationships between the solubility and molecular structure, common solvents, and the interaction energies of ion pairs, etc. were discussed systematically. The results showed that surface tension decreased linearly with temperature and decreased with the elongation of the alkyl chain length on cation and the decrease of interaction energies of ion pairs. With decreasing dielectric constant of solvent or the increase of the anion size, the solubility of the title ionic liquids decreased. With the elongation of the alkyl chain length, the interaction energies of ion pairs decreased, and the solubility in polar solvents had decreasing trend. The relationship between the surface tensions and solubility parameter for [VRIM]Br was expressed by using Hildebrand−Scoff equation. ■ INTRODUCTIONIonic liquids (ILs) are organic salts at room temperature or less than 300°C which are entirely composed of an organic cation (imidazolium, pyridinium, tetraalkylammonium, etc.) and an anion such as halide, triflate, amidotriflate, dicyanamide, tetrafluoroborate, hexafluorophosphate, etc. 1 The ionic character implies the extraordinary high ion density, and thus leads to the negligible vapor pressure (i.e, wide liquid temperature range and negligible flammability) and high ionic conductivity. 2,3 A key feature of ILs is that their physicochemical properties can be tailored virtually at will by varying their cations, substituents, and anions. 4−6 Research on structure and properties of ILs are mainly focused on melting point, conductivity, density, thermal stability, etc. at present, 7−17 which provide some theoretical basis for the structure analysis of ILs, the design and synthesis of novel functionalized ILs. 18,19 In addition, ILs have better solubility and surface activity; thus, they have been widely used in many scientific fields. 20−27 However, studies on the surface tension and solubility of ILs are still scarce, and the surface tensions of only a few of ILs have been reported; 28−32 Previous studies mainly have been done on the qualitative analysis of the solubility of ILs in organic or inorganic solvents, with little attention paid to the quantitative analysis of their solubility and the general law of solubility; The surface tension and solubility for most common ILs mainly concentrates on several N-alkyl-N-methylimidazolium ILs. 33−37 None of these studies have investigated the surface tension and the quantitative analysis of the solubil...

Investigation of Surface and Solubility Properties of N-Vinylimidazolium Tetrahalogenidoferrate(III) Magnetic Ionic Liquids Using Density Functional Theory

“…Because magnetism of the MILs interferes with the measuring signal, only 1 H NMR spectra for the intermediate ILs were measured. As can be seen from the data in Table , the results demonstrated that the synthetic compounds were [VRIM]­Br, [VRIM]­Cl, and [VEIM]­Cl …”

“…According to Scheme a, other intermediate ILs were synthesized adopting the route of [VBIM]­Br . On the basis of the results of 1 H NMR spectra, the mass fraction purity for the liquid ILs is >0.980, and for the solid ILs is >0.990 . The intermediate ILs are summarized in Table .…”

“…Only in 2014, four MILs based on the trihexyl­(tetradecyl)­phosphonium cation and different magnetic anions ([P 66614 ] 2 [CoCl 4 ], [P 66614 ]­[FeCl 4 ], [P 66614 ] 2 [MnCl 4 ], and [P 66614 ] 3 [GdCl 6 ]) were reported by measuring carbon dioxide solubility for CO 2 separation . And at the same year, our team investigated the surface properties and solubility of N -vinyl-3-alkyl/esterimidazolium halide ionic liquids . But, none of these studies have further investigated the surface tension and the quantitative analysis of the solubility for N -vinylimidazole-based MILs.…”

A Cobalt (II) Complex [Co(VIM)4](NCS)2 Based on 1-vinylimidazole (VIM) and SCN–

“…The three reasons can cause the increase of the solubility of the title complex in acetone. In the three reasons, the first one has been verified [24][25]. By the comparison with the As seen in Table 3, the solubility of the complex in chloroform is higher than that in ethyl acetate.…”

“…The carbon atom on the imidazolium ring is between two nitrogen atoms, which makes the carbon atom have part of positive charge ( +δ C-H), thus, the interaction between the carbon atom and the carbonyl oxygen (C=O δ-) becomes easier [24][25]. Secondly, due to the active hydrogen on the -CH 3 of acetone and the presence of abundant acetone in the solution, the hydrogen bond interaction (S…H) between NCS -and the active hydrogen on the imidazolium ring can exist.…”