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

N-Vinyl-3-alkylimidazolium tetrahalogenidoferrate(III) ([VRIM][FeX4], X4 = Cl3Br, Cl4) and N-vinyl-3-esterimidazolium tetrachloroferrate(III)([VEIM][FeCl4]) magnetic ionic liquids were synthesized. They were characterized by ¹H NMR, Raman, electrospray ionization mass spectrometry, differential scanning calorimetry and thermogravimetric analysis. Through Gaussian09/B3LYP/LANL2DZ density functional theory, the interaction energies of ion pairs and dipole moment of [VRIM][FeX4] and [VEIM][FeCl4] were obtained. The relationships between the surface tensions and temperature, molecular structure, and interaction energies of ion pairs along with the relationships between the solubility and molecular structure, common solvents, and interaction energies of ion pairs were discussed systematically. The relationship between the surface tensions and solubility parameter for [VRIM][FeX4] was expressed by using a Hildebrand-Scoff equation. And the hydrophilic-lipophilic balance (HLB) values of [VRIM][FeX4] were obtained by a solubility parameter. The results showed that surface tension decreased linearly with temperature and decreased with the elongation of alkyl chain length on cation and the decrease of interaction energies of ion pairs; With decreasing dielectric constant of solvent, the solubility of the title magnetic ionic liquids increased first and then decreased; with the elongation of alkyl chain length, the interaction energies of ion pairs and HLB value decreased, and the solubility in polar solvents had a decreasing trend. [ABSTRACT FROM AUTHOR]