Revealing the Effect of Hindered Weak Electrostatic Interactions of the Alkane Chain Length in the Imidazolium Chloride Ionic Liquids: A Molecular Electrostatic Potential Study

Abstract

The molecular electrostatic potential (MEP) provides the electron-rich and deficient regions within the molecular system, which enables the prediction of the noncovalent electrostatic interactions with other molecules. The alkane group attached to the nitrogen atom of the imidazolium ring plays an important role in the stabilization of ion pairs through electrostatic interactions such as hydrogen bonding. An inverse correlation between the ${\text{C}}_2-{\text{H}}_{C2}\text{⋯}{\text{Cl}}^{-}$ distance and the MEP at minimum near the ${\text{Cl}}^{-}$ anion revealed the presence of weak noncovalent electrostatic interactions between the positive potential of alkane chain hydrogen and the electron density of the ${\text{Cl}}^{-}$ anion. Consequently, a blue shift is noticed for ${\text{C}}_2-{\text{H}}_{C2}$ stretching vibration, which agrees well with the experimental results.