Structural and Spectroscopic Characterizations of Amide-AlCl3-Based Ionic Liquid Analogues

Several amide-AlCl3-based ionic liquid (IL) analogues were synthesized through a one-step method using three different structure amides as donor molecules. The effects of the steric and inductive effects of the methyl group substituted on the N atom on the asymmetric splitting of AlCl3 and the coordination site of the amide were investigated by Al-27 NMR, Raman, in situ IR, and UV-vis spectra for these IL analogues. Bidentate coordination through both the O and N atoms was dominant in the N-methylacetamide-AlCl3- and N,N-dimethylacetamide-AlCl3-based IL analogues because of the inductive effect of the methyl group. By contrast, the acetamide-AlCl3-based IL analogue presented mainly in the form of monodentate coordination via the O atom. Compared with monodentate coordination, bidentate coordination was favorable to the asymmetric splitting of AlCl3 with the same amide-AlCl3 molar ratio. Under the influence of the steric and inductive effects of the methyl group, the ionic species percentages in these IL analogues ranked in the following order: N-methylacetamide > N,N-dimethylacetamide > acetamide.