Two-Dimensional Organic Brick-Wall Layers as Hosts for the Inclusion and Study of Aromatics Ensembles: Acid−Pyridine and Acid−Carbonyl Synthons for Multicomponent Materials

The compound trimesic acid (H₃TMA) with 2,6-bis(4-pyridylmethylene)cyclohexanone (1) was shown to form two-/three-/four-component cocrystals or salts depending on the reaction conditions. Crystals of salt were obtained when crystallized H₃TMA and 1 from MeOH alone, whereas the crystals of neutral components were obtained when crystallized from MeOH and phenol mixture. Both the structures (salt and cocrystal) exhibited huge cavities which are occupied by the self-interpenetration of the networks. This self-interpenetration of the networks found to be eschewed in favor of guest inclusion when the crystallization reactions are conducted in the presence of suitable aromatic guest molecules such as biphenyl, naphthalene, anthracene, phenanthrene, pyrene, triphenylene, and 1,4-hydroquinone. The crystal structures of cocrystals contain hydrogen-bonded layers with huge cavities, the self-interpenetrated layers have a honeycomb geometry with the cavity dimensions of 23 × 42 Ų and the guest included layers have a brick wall geometry with cavity sizes of 8 × 23 Ų. The guest occupied volume of these materials varies from 12 to 38% of crystal volume. In the four-component systems, the adducts of guest molecules were found between pyrene-phenol, pyrene-1,4-hydroquinone, and phenanthrene-o-cresol. In three-component systems, the packing of guest biphenyls is similar to that of the biphenyl crystal structure itself.