Investigation On The Influence Of H₂O/CH₃OH On The Structure Of The Amino Acid Ionic Liquid

In this work, novel amino acid ionic liquids (AAILs)[bmim][Gly](1-butyl-3-methylimidazolium glycine acid salt),[bmim][Gly] and Water/Methanol,[Bmim][Ala](1-butyl-3-methylimidazolium α-aminopropionic acid salt) and [Bmim][Ala]and Water/Methanol have been systematically studied by the density functional theory (DFT)at the B3LYP/6-311++G**level. The mechanism of the cation-anion interaction and therelated micro-properties of the system have been illuminatedFirst,[bmim]+[Ala]-、[bmim]+[Gly]-were systematically studied. The stable geometriesof the [bmim]+[Ala]-、[bmim]+[Gly]-with no imaginary frequencies were obtained andcharacterized. The interaction energies between the cation and the anion were calculated. Theresults show that the multiple intermolecular hydrogen bonds together with the electrostaticinteraction play an important role in stabilizing the cation–anion system. The favorable sitesfor the cation–anion interaction have been determined.The structures of the lowest energy were chosen. The natural bond orbital (NBO) andatoms in molecule (AIM) analyses have also been applied to understand the nature of theinteractions between the AAILs and Water/Methanol. The most stable geometries have beendetermined by analyzing the relative energies and interaction energies, where the C-H···Ointermolecular H bonds involving the protons attached to the imidazolium ring have beenfound to possess partial covalent character in nature. Infrared spectroscopy and Ramanspectroscopy play important roles in investigations on the structural properties andinteractions of AAILs and Water/Methanol.The stable geometries of the cation and Water, anion and Water, ion pair, as well as theion-pair and the Two Water/Methanol with no imaginary frequencies were obtained andcharacterized, which will help us to understand the position of hydrogen bonds and make ourlogical integrity.We explained the hydrogen bonding effect on the microstructure and microscopicproperties. Finally, through the combination of the ATR-FTIR spectroscopy experiments andtheoretical spectra, experimental results could be illustrated by the theoretical calculations,and also the experiments proved the reliability of the calculations. Exploring the changing lawof the macroscopic properties of ionic liquids along with the micro-structural changes,ultimately a reasonable explanation of the microscopic structure of [bmim][Gly]/Watersolution,[bmim][Gly]/Methanol,[Bmim][Ala] and Water/Methanol solutions could berealized.