posted on 2020-09-29, 22:07authored byAnjali Gaur, Nikhil V. S. Avula, Sundaram Balasubramanian
The fluorination
efficiency of a fluorinating agent depends on
the free availability of the fluoride ions, which in turn depends
on its interaction with its solvation shell. A stable fluoride-based
poor solvate ionic liquid (SIL) comprising 1-ethyl-3-methylimidazolium
(EMIM) cation and ethylene glycol (EG) was recently reported and demonstrated
as a fluorinating agent. Herein, we performed ab initio calculations and ab initio molecular dynamics simulations
to gain a microscopic understanding of the intermolecular interactions
in this SIL in gas, liquid, and crystalline phases. Ethylene glycol
(EG), being capable of forming hydrogen bond(s) with the fluoride
ion, prevents the latter from reacting with the EMIM cation. Fluoride
forms hydrogen bonds with both the cation and the EG molecule, but
it was found to have more affinity toward EG, forming a stronger hydrogen
bond with its hydroxyl proton than with the acidic proton of the cation.
An optimal concentration of EG in the SIL balances its contribution
to stabilizing the fluoride ion and yet making fluoride available
for fluorination.