Novel Supramolecular Heterosynthons [C–I···NN] and [C–I···π(CC)]

• Published in: Crystal growth & design 2024-10, Vol.24 (20), p.8319-8333
• Main Authors: Torubaev, Yury. V., Skabitsky, Ivan V.
• Format: Article
• Language: English
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/acs.cgd.4c00794

Heteromolecular C–I···π­(CC) and C–I···(LEP)­NN (LEP lone electron pair) have been observed for the first time in cocrystals of diphenylacetylene (tolan, Ph2C2) and azobenzene (Ph2N2) with halogen bond donor, diiodoacetylene (C2I2). Computational analysis (density functional theory (DFT), molecular electrostatic potential (MEP), quantum theory of atoms in molecules (QTAIM)) indicates that C–I···π­(CC) and C–I···(LEP)­NN interactions are stronger than I···π­(Ph), which is also possible between iodo-XB donors and Ph2C2 or Ph2N2. However, cocrystallization of Ph2C2 and Ph2N2 with isomeric series of o-, m-, p-diiodotetrafluorobenzenes (1,2-, 1,3-, 1,4-DITFB) and pentafluoroiodobenzene (C6F5I) afforded the cocrystals stabilized predominantly by the relatively weaker I···π­(Ph) interactions, while 1,3-DITFB featured both I···π­(CC) and I···π­(Ph) halogen bonds. Analysis of the interplay of intermolecular interactions and energetic, molecular symmetry, and packing factors in cocrystals revealed a complex structural landscape and suggested the lowering of molecular symmetry to achieve the desired [C–I···π­(CC)] and [C–I···(LEP)­NN] for diiodotetrafluorobenzene coformers. Besides these promising structural motifs, we discuss here the formation of chiral cocrystal structures from achiral coformers and high-Z′ structure Ph2N2 1,2-DITFB (2:3).