Evaluating structure-property relationship in a new family of mechanically flexible co-crystals.

A structure-property analysis of ten compositionally and chemically similar co-crystals of -(pyridin-2-yl)alkylamides and carboxylic acids shows that three co-crystals of targets bearing a methyl chain were brittle, while the remaining co-crystals of targets bearing ethyl or propyl chains were flexible. Five of these displayed elastic deformation while two displayed plastic deformation. Compounds with different mechanical behaviour (brittle, plastic, and elastic deformation) in response to external mechanical stimuli could be organized into structurally similar groups based on the presence of specific intermolecular interactions and packing features in each crystal structure.

Intermolecular binding preferences of haloethynyl halogen-bond donors as a function of molecular electrostatic potentials in a family of -(pyridin-2-yl)amides.

In order to explore how σ-hole potentials, as evaluated by molecular electrostatic potential (MEP) calculations, affect the ability of halogen atoms to engage in structure-directing intermolecular interactions, we synthesized four series of ethynyl halogen-substituted amide containing pyridines (activated targets); (N-(pyridin-2-yl)benzamides (Bz-act-X), N-(pyridin-2-yl)picolinamides (2act-X), N-(pyridin-2-yl)nicotinamides (3act-X) and N-(pyridin-2-yl) isonicotinamides (4act-X), where X = Cl/Br/I. The molecules are deliberately equipped with three distinctly different halogen-bond acceptor sites, π, N(pyr), and O[double bond, length as m-dash]C, to determine binding site preferences of different halogen-bond donors. Crystallographic data for ten (out of a possible twelve) new compounds were thus analyzed and compared with data for the corresponding unactivated species.

Establishing Halogen-Bond Preferences in Molecules with Multiple Acceptor Sites.

The interplay between hydrogen bonds (HBs) and halogen bonds (XBs), has been addressed by co-crystallizing two halogen bond donors, 1,4-diiodotetrafluorbenzene(DITFB) and 1,3,5-trifluoro-2,4,6-triiodobenzene(TITFB) with four series of targets; N-(pyridin-2-yl)benzamide (Bz-X), N-(pyridin-2-yl)picolinamides (2Pyr-X), N-(pyridin-2-yl)nicotinamides (3Pyr-X), N-(pyridin-2-yl)isonicotinamides (4Pyr-X); X=H/Cl/Br/I. The structural outcomes were compared with interactions in the targets themselves. 13 co-crystals were analysed by single-crystal X-ray diffraction (SCXRD).

The Impact of Halogen Substituents on the Synthesis and Structure of Co-Crystals of Pyridine Amides.

Strategies for co-crystal synthesis tend to employ either hydrogen- or halogen-bonds between different molecules. However, when both interactions are present, the structural influence that they may exert on the resulting assembly is difficult to predict a priori. To shed some light on this supramolecular challenge, we attempted to co-crystallize ten aliphatic dicarboxylic acids (co-formers) with three groups of target molecules; -(pyridin-2-yl)picolinamides (2Pyr-), -(pyridin-2-yl)nicotinamides (3Pyr-), -(pyridin-2-yl)isonicotinamides (4Pyr-); X=Cl/ Br/ I.