Supramolecular hierarchy among halogen-bond donors

Area of Science:

• Supramolecular Chemistry
• Crystal Engineering
• Chemical Physics

Background:

• Halogen bonding (XB) is a crucial non-covalent interaction in supramolecular chemistry.
• Understanding the relative importance of different XB donors is essential for predictable crystal design.
• Systematic studies are needed to map the supramolecular landscape influenced by various XB donors.

Purpose of the Study:

• To systematically investigate and rank the structure-directing capabilities of ditopic halogen-bond (XB) donors.
• To elucidate the competition between different classes of XB donors (ethynyl, perfluorinated, and phenyl-based) in co-crystallization.
• To provide practical guidelines for synthetic crystal engineering based on halogen bonding.

Main Methods:

• Utilized a combination of structural chemistry, vibrational spectroscopy, and theoretical calculations.
• Evaluated molecular electrostatic potential surfaces of six XB donors for charge-based ranking.
• Performed co-crystallization experiments with 21 XB acceptors to map supramolecular interactions.

Main Results:

• Established a charge-based ranking of the six ditopic XB donors.
• Mapped the supramolecular landscape, detailing the competitive interactions involving I/Br-ethynyl, perfluorinated I/Br, and I/Br-phenyl donors.
• Demonstrated the influence of XB donor structure on the resulting supramolecular assemblies.

Conclusions:

• The study provides a systematic framework for understanding and predicting halogen-bond donor effectiveness.
• The findings offer practical guidelines for designing and synthesizing crystalline materials using directional halogen bonds.
• This research advances the field of crystal engineering by offering predictable control over supramolecular assembly.