pi-Complexation and C-H hydrogen bonding in the formation of colored cocrystals

The present study evaluates the potential combination of charge-transfer electron-donor-acceptor pi-pi complexation and C-H hydrogen bonding to form colored cocrystals. The crystal structures of the red 1:1 cocrystals formed from the isomeric pyridines 4- and 3-{2-[4-(dimethylamino)phenyl]ethynyl}pyridine with 1-[2-(3,5-dinitrophenyl)ethynyl]-2,3,5,6-tetrafluorobenzene, both C14H4F4N2O4 center dot C15H14N2, are reported. Intermolecular interaction energy calculations confirm that pi-stacking interactions dominate the intermolecular interactions within each crystal structure. The close contacts revealed by Hirshfeld surface calculations are predominantly C-H interactions with N, O, and F atoms.