Reversibility of imido-based ionic liquids: a theoretical and experimental study

Abstract

Multiple techniques were used to study the reversibility of a series of imido-based ionic liquids (ILs). DFT (density functional theory) modeling originally indicated that methyl transfer favorably took place at the unsaturated CX bond in the N–CX (N, O and S) fragment. A series of imido-based ILs derived from the N–CX (N, O and S) fragment were studied and characterized using theoretical and experimental methods. Seven imido-based ILs were facilely synthesized in the experiment, which is consistent with the lower energy barriers obtained in the potential energy surface (PES) compared to the other ILs. Their structures were measured in nuclear magnetic resonance (NMR) spectra. The thermal stabilities were further studied by thermogravimetric analysis (TGA). The bond order results indicated that non-covalent interactions were the major driving force in the methyl transfer process. Non-covalent interactions in these ILs were investigated and characterized using atoms in molecules (AIM), reduced density gradient (RDG) and natural bond orbital (NBO) methods.