Self-assembly of thermotropic liquid-crystalline folic acid derivatives: hydrogen-bonded complexes forming layers and columns

Folic acid derivatives having 2-(3,4-dialkoxyphenyl) ethyl moieties have been found to exhibit thermotropic liquid-crystalline behavior. Smectic and discotic phases are observed for these compounds over wide temperature ranges. X-Ray diffraction and infrared measurements show that the formation of the smectic and discotic phases is due to the ribbon-and disk-like structures of the pterin rings of folic acid, respectively. The smectic phase is changed to a hexagonal columnar phase by the addition of alkali metal salts. This behavior is attributed to the change of the hydrogen-bonded structures from ribbon to disk induced by the ion-dipolar interactions.