The Energy Frameworks of Aufbau Synthon Modules in 4-Cyanopyridine Co-crystals.
Supramolecular arrangement of 4-cyanopyridine (4CNpy) in the native crystal and its co-crystals with the halogen bond (XB) donors is considered in terms of long-range synthon Aufbau modules (LSAM) and energy frameworks. Dissociations of 2D zig-zag chains of parent 4CNpy into 1D dimers observed in its co-crystals are in good agreement with the aufbau model. Its co-formers, XB donors 1,4-I2(CF2)4, C2I2, 1,3- and 1,4-I2C6F4 (m- and p-DITFB) provide equal energy of I---N XBs, but perfluorinated iodo-alkane 1,4-I2 (CF2)4 and diiodoacetylene C2I2 could not achieve the same strength of homomolecular aggregation as π-π stacking in columnar p-DITFB modules. As a result, DITFBs forms I---N XBs with both Npy and NCN nitrogen atoms of 4CNpy, while 1,4-I2(CF2)4 and C2I2 - only with Npy atom. This is not a particular case of 4CNpy co-crystals, but in general, DITFB appears more effective XB donor co-former than 1,4-I2(CF2)n, C2I2 and other iodo- XB donors, which has similar potential on iodine atom but lacking homomolecular aggregation. In supramolecular reactions of (η6-Ar)RuX2(4CNPy) (Ar = p-cymene, X=Cl, I) bearing Npy-coordinated 4CNpy, with p-DITFB, the latter gives definite preference to the XBs with the halogen atoms, but not to the CN group of 4CNpy ligand.
- This article is part of the themed collection: 1st International Conference on Noncovalent Interactions