Insight into the structure and interaction properties of 1-propylnitrile-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and chloroform mixtures

In this work, the structure and interaction properties of the mixtures of a task specific ionic liquid (TSIL) 1-propylnitrile-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([PCNMIM][Tf₂ N]) and chloroform (CDCl₃ ) were elucidated by Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations. Excess infrared spectroscopy was applied to analyse the original infrared spectra. The main conclusions are: (1) stable hydrogen-bonding complexes are found in the mixtures, and they are the primary cause of the gradual shift of v (C–H) of the [PCNMIM]⁺ cation. The hydrogen-bonds related to the aromatic C–H are strengthened, while those related to the alkyl C–H are weakened by the addition of CDCl₃ . (2) A number of species in the binary mixtures were identified, namely, ion cluster–CDCl₃ , ion pair–CDCl₃ , ion pair and ion cluster. CDCl₃ cannot break apart the strong electronic interaction between [PCNMIM] ⁺ and [Tf₂N] ⁻ but can break apart the ion cluster into ion pair throughout the investigated concentration range. (3) Several hydrogen-bonds are identified in the ion cluster–CDCl ₃ , ion pair–CDCl₃ , ion pair and ion cluster complexes. They are weak strength, closed shell and electrostatic dominant interactions. In addition, the hydrogen atom at the C2 site of the [PCNMIM] ⁺ cation is the preferred interaction site.