Owing to their unique properties, ionic liquids (ILs) nowadays are very fascinating in various fields, including organic synthesis, catalysis, inorganic chemistry, electrochemistry, and materials. The determination the strength of the intrinsic electric fields in ILs is of fundamental importance to the understanding of the properties of ILs and their applications. Unfortunately, until now the intrinsic electric fields in ILs have remained poorly understood, and their identification and quantification are very challenging.

Researchers at R&D Center for Green Chemistry and Catalysis, Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences (CAS), have, for the first time, successfully applied the vibrational Stark effect (VSE) spectroscopy to measure the intrinsic electric fields in ILs, and have carried out an evaluation of the results by performing molecular dynamics (MD) simulations. The results show that the electric fields of ionic liquids are only slightly higher than those of common molecular solvents, and are strongly structure-dependent. They noticeably decrease with the increasing of the size of anion and cation.

This work provides a systematic way to evaluate the ionic environment and the intrinsic electric fields in ILs and improves the understanding of the ionic nature of ILs.

The work has received support from the National Natural Science Foundation of China . The findings have been published in Chem. Eur. J.(Chem. Eur. J.2012, 18, 11904 – 11908).

Determination of intrinsic electric fields in ILs using vibrational Stark effect (VSE) spectroscopy and molecular dynamics (MD) simulations