Controlling the Crystal Packing and Morphology of Metal–Organic Macrocycles through Side-Chain Modification

• Published in: ACS materials letters Vol. 6; no. 7; pp. 3043 - 3049
• Main Authors: Zasada, Leo B., Le, Phuong H., Hill, Audrey M., Shafranek, Ryan T., Xiao, Dianne J.
• Format: Journal Article
• Language: English
• Published: American Chemical Society 01.07.2024
• ISSN: 2639-4979; 2639-4979
• DOI: 10.1021/acsmaterialslett.4c00957

Supramolecular nanotubes constructed from the self-assembly of conjugated metal–organic macrocycles provide a unique collection of materials properties, including solution processability, porosity, and electrical conductivity. Here we show how small modifications to the macrocycle periphery subtly alter the noncovalent interactions governing self-assembly, leading to large changes in crystal packing, crystal morphology, and materials properties. Specifically, we synthesized five distinct copper-based macrocycles that differ in either the steric bulk, polarity, or hydrogen-bonding ability of the peripheral side chains. We show that the electrical conductivity of these macrocycles is highly sensitive to steric bulk, decreasing by 3 orders of magnitude upon introduction of peripheral neopentyl substituents. We further show that the introduction of hydrogen-bonding groups leads to more ordered packing and a dramatic increase in crystallite size. Together, these results establish side-chain engineering as a rich toolkit for controlling the packing structure, particle morphology, and bulk properties of conjugated metal–organic macrocycles.