Designed cocrystals based on the pyridine-iodoalkyne halogen bond.

Area of Science:

• Crystal engineering
• Supramolecular chemistry
• Organic synthesis

Background:

• Halogen bonding is a key non-covalent interaction in crystal engineering.
• Polyyne compounds are precursors for carbon-rich materials and polymers.
• Bispyridyl oxalamides and ureas are versatile host molecules for supramolecular assembly.

Purpose of the Study:

• To investigate the cocrystallization of diiodobutadiyne and diiodohexatriyne with bispyridyl oxalamides and ureas.
• To explore the role of halogen bonding in directing the assembly of these polyyne cocrystals.
• To assess the potential for topochemical polymerization within the formed cocrystal structures.

Main Methods:

• Cocrystallization experiments were performed using diiodobutadiyne (1) and diiodohexatriyne (2) with various bispyridyl oxalamides and ureas.
• Single-crystal X-ray diffraction was employed to determine the structures of the resulting cocrystals.
• Analysis of intermolecular interactions, including halogen bonds and hydrogen bonds, was conducted.

Main Results:

• Cocrystals of diiodobutadiyne and diiodohexatriyne with bispyridyl oxalamides and ureas were successfully synthesized.
• Halogen bonds between alkynyl iodine atoms and pyridine nitrogen atoms were identified as the primary interaction driving cocrystal formation.
• The host molecules formed one-dimensional hydrogen-bonded networks that effectively aligned the diiodopolyyne guests.
• The repeat distances within the host networks were found to match the dimensions required for potential topochemical polymerization.

Conclusions:

• Diiodobutadiynes and diiodohexatriynes can form well-defined cocrystals with bispyridyl oxalamides and ureas.
• Halogen bonding and hydrogen bonding synergistically control the supramolecular architecture of these cocrystals.
• The aligned arrangement of polyynes within these cocrystals presents a promising platform for controlled topochemical polymerization.