# Mapping the Crystallographic Landscape of Antivitamin Ionic Liquids: Structural Blueprints for Novel Architectures

## TL;DR

This study explores the crystal structures of antivitamin-based ionic liquids, revealing insights into their low melting points and unique structural features.

## Contribution

The paper reports the first crystallographic study of antivitamin-derived ionic liquids and identifies novel structural features influencing their properties.

## Key findings

- Seven new amprolium salts with various anions were synthesized and structurally analyzed.
- Key structural features like conformational disorder and hydrogen bonding were identified as factors influencing low melting points.
- Hydrogen interactions dominated intermolecular forces, with oxygen and fluorine being primary H-bonding sites.

## Abstract

This work presents the first in-depth crystallographic
study of
antivitamin-derived ionic liquids. Seven new amprolium salts incorporating
hallmark ionic-liquid anions such as bis­(trifluoromethanesulfonyl)­imide
(NTf2
–), bis­(pentafluoroethanesulfonyl)­imide
(BETI–), tetrafluoroborate (BF4
–), and hexafluorophosphate (PF6
–) were
synthesized and crystallized, and their structures and interactions
were elucidated through crystallographic and computational analyses.
The well-documented biological functions of amprolium can help simplify
future applications of these compounds as well as open the pathway
for the development of novel cations for ionic liquid development.
Despite their dicationic nature and bearing multiple H-bonding donors
and acceptors, these compounds exhibited unexpectedly low melting
points and displayed challenging crystallization conditions. The analysis
identified key structural features explaining this behavior: (i) two
points of conformational disorder in the pyrimidine ring and propyl
moiety; (ii) three distinct cation conformations affecting aromatic
components; and (iii) novel high-energy conformations of anions, reported
here for the first time. Hydrogen interactions dominated intermolecular
forces (85% of total interactions), with H-bonding to oxygen and fluorine
being most prevalent. These insights advance our understanding of
how to engineer functional materials from natural sources for potential
applications in sustainability and medicine. The combined experimental-computational
approach validates these design principles, providing a foundation
for more targeted development of similar compounds with tailored properties.