Self-Assembly and Polymorphic Transformation of Butterfly-Shaped Organic Nanocrystals from a Windmill-like Bulky Small Molecule

• Published in: Crystal growth & design Vol. 21; no. 2; pp. 1113 - 1121
• Main Authors: Li, Yin-Xiang, Yu, Meng-Na, Eginligil, Mustafa, Wang, Sha-Sha, Liu, Ju-Qing, Xie, Ling-Hai, Dong, Xue-Mei, Huang, Wei
• Format: Journal Article
• Language: English
• Published: American Chemical Society 03.02.2021
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/acs.cgd.0c01440

Here, biomimetic organic nanocrystals with a butterfly-like morphology (BM) were first constructed from a windmill-like bulky small molecule, T­(DAF)3. The BMs possess a peculiar “Janus” feature with a butterfly-shaped front side and cross-veined back side. Evolution observations clearly reveal that this unusual 3D architecture is originated from the preferential growth of {011} and {0–11} crystal faces of a core. Additionally, the BMs are pH-sensitive and can be converted reversibly with a cube-shaped morphology (CM). Detailed microscopic observations in combination with systematically single-crystal determinations suggest that the BMs and CMs are polymorphs and the acid/base responsive conformational conversion of T­(DAF)3 is responsible for the polymorphic transformation. Finally, the effect of molecular-level conformation on packing and morphology is demonstrated. The nonplanar 3D configuration, flexible conformational transitions, and variable supramolecular interactions of T­(DAF)3 are regarded as the crucial factors for the realization of the biomimetic morphology and polymorphic transformation of organic microcrystals. The rotational isomerism-morphology relationship of organic small molecules can serve as a model, providing a guideline for complex micro/nanocrystals of organic systems for optoelectronic or bionic applications.