Elimination of Interionic Hydrogen Bonding in the Imidazolium-Based Ionic Liquids

TL;DR

This paper explores how chemical modifications can eliminate hydrogen bonding in imidazolium-based ionic liquids, leading to altered properties and improved design for specific applications.

Contribution

It demonstrates that modifying the tetrafluoroborate anion removes hydrogen bonding and changes cation orientation, providing new insights for designing better ionic liquids.

Findings

Hydrogen bonding can be eliminated through anion modification.

Modified anions alter cation orientation and electrostatic interactions.

New physical insights enable tuning of ionic liquid properties.

Abstract

Hydrogen bonding is a phenomenon of paramount importance in room-temperature ionic liquids. The presence or absence of the hydrogen bond drastically alternates self-diffusion, shear viscosity, phase transition points, and other key properties of a pure substance. For certain applications, the presence of cation-anion hydrogen bonding is undesirable. In the present paper, we investigate perspectives of removing the hydrogen...fluorine interionic attraction in the imidazolium borates, the strongest non-covalent interaction in this type of system. Chemical modification of the tetrafluoroborate anion not only eliminates hydrogen bonding but also changes the most thermodynamically preferable orientation of the cation in the vicinity of the anion. Although the most acidic hydrogen atom of the imidazole ring remains the paramount electrophilic center of the cation, it does not engender a strong electrostatically driven coordination pattern with the properly modified anions. The reported new physical insights help compose more robust ionic liquids and tune solvation properties of the imidazolium-based RTILs.