Effect of π–π Interactions on Morphology of Nonplanar Binary Halogen-Bonded Cocrystals

The application of organic crystal in different photoelectric device has different demand on the crystal structure and morphology, while the self-assembly of different materials into crystals with a desired morphology remains a challenge. Herein, using three binary halogen-bonded cocrystals involving a nonplanar halogen accepter molecule tetra(4-pyridyl)-tetrathiafulvalene (TTF(py)₄), co-crystallized with halogen donor aryl iodides C₆F_6-xI_x (x = 2,3, 1,3,5-trifluoro-2,4,6-triiodobenzene (IFB), meta-1,3-diiodotetrafluorobenzene (mdIFB) or para-1,3-diiodotetrafluorobenzene (pdIFB)), are reported. TTF(py)₄-IFB cocrystals are formed primarily via N···I halogen bonds and F···H hydrogen bonds, while TTF(py)₄-mdIFB cocrystals and TTF(py)₄-pdIFB cocrystals are formed primarily via π–π Interactions, N···I halogen bonds and F···H hydrogen bonds, homogeneous π–π interactions are dominant in TTF(py)₄-mdIFB, while heterogeneous π–π interactions are dominant in TTF(py)₄-pdIFB. Through predicted morphology based on the attachment energy (E_att) theory, especially π–π interaction, the influence of intermolecular interactions on crystal morphology is analyzed. The study demonstrates that the π–π interaction plays an important role in regulating the crystal structure and morphology, the work provides a deeper understanding of π–π interactions in nonplanar binary halogen-bonded cocrystals.