The energy frameworks of aufbau synthon modules in 4-cyanopyridine co-crystals

• Published in: CrystEngComm 2019, Vol.21 (46), p.757-768
• Main Authors: Torubaev, Y. V, Skabitsky, I. V
• Format: Article
• Language: English
• Subjects: Agglomeration; Alkanes; Crystallography; Crystals; Dimers; Donors (electronic); Iodine; Modules; Nitrogen atoms
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/c9ce01174a

The supramolecular arrangement of 4-cyanopyridine (4CNpy) in its native crystal form and its co-crystals with halogen bond (XB) donors is discussed in terms of long-range synthon aufbau modules (LSAMs) and energy frameworks. Dissociations of 2D zigzag 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-I 2 (CF 2 ) 4 , C 2 I 2 , 1,3- and 1,4-I 2 C 6 F 4 ( m - and p -DITFB), provide equal energy of I N XBs, but perfluorinated iodo-alkane 1,4-I 2 (CF 2 ) 4 and diiodoacetylene C 2 I 2 cannot achieve the same strength of homomolecular aggregation as π-π stacking in columnar DITFB modules. As a result, DITFBs form I N XBs with both N py and N CN nitrogen atoms of 4CNpy, while 1,4-I 2 (CF 2 ) 4 and C 2 I 2 only with the N py atom. This is not a particular case of 4CNpy co-crystals, but in general, DITFB appears to be a more effective XB donor co-former than C 2 I 2 , 1,4-I 2 (CF 2 ) n and other iodo-XB donors, which has similar potential to an iodine atom but lacks homomolecular aggregation. In supramolecular reactions of p -DITFB with (η 6 -Ar)RuX 2 (4CNpy) (Ar = p -cymene, X = Cl, I) bearing N py -coordinated 4CNpy, the former gives definite preference to the XBs with the halogen atoms, but not to the CN group of the 4CNpy ligand. The supramolecular arrangement of 4-cyanopyridine (4CNpy) in its native crystal form and its co-crystals with halogen bond (XB) donors is discussed in terms of energy frameworks of long-range synthon aufbau modules (LSAMs) energy frameworks.