Thermodynamic Properties and Intermolecular Interacting Behaviors of Amino-Functionalized Ionic Liquid Binary Mixtures of 1-Aminopropyl-3-methylimidazolium Tetrafluoroborate with Dimethyl Sulfoxide and Acetonitrile

Amino-functionalized ionic liquids are potential and promising media for CO2 absorption, separation, and biocatalysts due to their greenness, favorable fluidity, higher positive charge density, and rich pore structure characteristics. Two new binary mixtures, {1-aminopropyl-3-methylimidazolium tetrafluoroborate ([NH2-Pmim][BF4]) + dimethyl sulfoxide (DMSO)} and {[NH2-Pmim][BF4] + acetonitrile (ACN)}, were prepared to investigate the thermodynamic properties and internal interaction behaviors. First, the thermodynamic properties such as dynamic viscosity, density, electrical conductivity, and refractive index of the two mixture systems over the entire concentration range were measured from 288.15 to 353.15 K. By the Arrhenius equation and Vogel-Fulcher-Tamman (VFT) equation, the temperature dependence on electrical conductivity was graphically described. To investigate the internal interactions of the mixtures, the excess molar volume (V-E), and viscosity deviation (Delta eta) were calculated and discussed by using the measured experimental data and Redlich-Kister equation fitting. Further, the structures and energies of the cation, anion, ion pairs, and solvent molecules were obtained by density functional theory (DFT) calculations to evaluate the intermolecular interactions among the different components of the mixture systems. Also the sigma-profile provided the relationship between hydrogen bond donor and acceptor between IL and solvents.