Theoretical investigation of interactions between glycine cation based ionic liquids and water molecules

To investigate the interactions between water molecules and amino acid cation based ionic liquids (ILs), systematic quantum chemistry calculations were performed on the system composed of one HGlyBF4 (Gly, glycine) IL molecule and one water molecule. Geometry optimizations on the system in gas phase were performed with B3LYP/6-31+G(d,2p), B3LYP/6-311++G∗∗ and MP2/6-311++G∗∗ methods, and the vibration frequencies of each optimized molecule were analyzed with the first two methods. The interaction energies between HGlyBF4 and H2O molecule were calculated and the basis set superposition error (BSSE) was corrected with counterpoise method (CP). It was found that comparing with traditional ILs based on imidazolium cations, this new generation ILs derived from amino acids is more hydrophilic for that the HGly+ cation part is also hydrophilic. The optimizations of HGlyBF4-nH2O (n = 2, 6) systems were also performed.