π-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 π-π 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 C 14 H 4 F 4 N 2 O 4 ·C 15 H 14 N 2 , are reported. Intermolecular interaction energy calculations confirm that π-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.