2,3,5,6-Tetramethyl-1,4-diisocyanobenzene (1), 1,4-diisocyanobenzene (2), and 1,4-dicyanobenzene (3) were co-crystallized with 1,3,5-triiodotrifluorobenzene (1,3,5-FIB) to give three cocrystals, 1·1,3,5-FIB, 2·2(1,3,5-FIB), and 3·2(1,3,5-FIB), which were studied by XRD. Common feature of the three structures is the presence of I···Cisocyanide or I···Nnitrile HaBs occurred between an iodine -hole and the isocyanide C- (or the nitrile N-) atom. The diisocyanide and dinitrile cocrystals, 2·2(1,3,5-FIB) and 3·2(1,3,5-FIB), are isostructural thus providing a basis for accurate comparison of the two types of noncovalent linkages of CN/NC groups in the composition of structurally similar entities and in one crystal environment. The bonding situation was studied by a set of theoretical methods. Diisocyanides are more nucleophilic than the dinitrile and they exhibit stronger binding to 1,3,5-FIB. In all structures, the HaBs are mostly determined by the electrostatic interactions, but the dispersion and induction components also provide a noticeable contribution and make the HaBs attractive. Charge transfer has a small contribution (<5%) to the HaB and it is higher for the diisocyanide than for the dinitrile systems. At the same time, diisocyanide and dinitrile structures exhibit typical electron-donor and -acceptor properties in relation to the HaB donor.
Chemistry and Materials Science, Physical Chemistry
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