Complex structures arising from the self-assembly of a simple organic salt

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Crystallography

Background:

• Molecular self-assembly is fundamental to natural processes and materials design.
• Understanding self-assembly rules for small organic molecules remains a challenge.
• Frank-Kasper (FK) phases, known in alloys and soft matter, are complex structures.

Purpose of the Study:

• To investigate the self-assembly behavior of a simple fampridine hydrochloride salt.
• To identify and characterize novel crystalline structures formed by molecular self-assembly.
• To explore the formation of complex polyhedral clusters in organic systems.

Main Methods:

• Crystallization of fampridine hydrochloride.
• Structural analysis of resulting crystalline phases.
• Cryogenic electron microscopy of the precursor dense liquid phase.

Main Results:

• Identified four distinct crystalline structures of fampridine hydrochloride.
• Discovered two unusual FK phases with polyhedral clusters of ions.
• Observed spherical aggregates (1.5–4.6 nm) in the precursor liquid phase.
• These FK phases exhibit complexity typically not seen in small organic molecules.

Conclusions:

• Fampridine hydrochloride forms complex FK phases, expanding the known structures for small organic molecules.
• The findings suggest new possibilities for designing organic crystalline materials with tailored properties.
• Further research into the formation mechanisms of these aggregates is warranted.