Isocyanide and Cyanide Entities Form Isostructural Halogen Bond-Based Supramolecular Networks Featuring Five-Center Tetrafurcated Halogen···C/N Bonding

• Published in: Crystal growth & design 2022-10, Vol.22 (10), p.6079-6087
• Main Authors: Mikherdov, Alexander S., Popov, Roman A., Smirnov, Andrey S., Eliseeva, Anastasiya A., Novikov, Alexander S., Boyarskiy, Vadim P., Gomila, Rosa M., Frontera, Antonio, Kukushkin, Vadim Yu, Bokach, Nadezhda A.
• Format: Article
• Language: English
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/acs.cgd.2c00686

A typical halogen bond (HaB) donor, 1,4-dibromo-2,3,5,6-tetrafluorobenzene (FBB), was cocrystallized with the isocyanide CNMes and the cyanide NCMes to give two isostructural cocrystals, (CNMes)·FBB and (NCMes)·FBB. Their solid-state architecture exhibits a close similarity between the isocyanide and cyanide groups in their HaB-accepting role. This similarity and particular bonding features of the HaBs were additionally verified by theoretical calculations (molecular electrostatic potential analysis, electron density/electrostatic potential profiles, atoms-in-molecules charge analysis, and calculations of pK a values and binding energies). Remarkably, both cocrystals form unusual heterohexamers where one Br atom of FBB simultaneously forms four contacts with two C (or N) and two Br atoms of neighboring molecules. On the basis of the geometric parameters and the theoretical data, these contacts can be defined as five-center tetrafurcated μ4-Br···(C, Br, C, Br) and μ4-Br···(N, Br, N, Br) HaBs; this is the first observation of the tetrafurcated HaB involving four disunited HaB acceptors.