PHOTOCHEMICAL BEHAVIOR OF A DISCOID, CINNAMOYL-SUBSTITUTED AZACROWN DERIVATIVE - ISOMERIZATION AND CROSS-LINKING IN THE ORDERED STATE

The photochemistry of a discoid, mesogenic hexa-cinnamoyl-substituted hexacyclen, which is mainly determined by the competition between E/Z-photoisomerization and (2 + 2)-photocycloaddition, is investigated in solution and in bulk. In a poor solvent, such as cyclohexane, columnar aggregates are supposed to be formed, due to the amphiphilic structure of the hexacyclen. Upon irradiation, these preformed aggregates undergo intracolumnar photocycloaddition between the photoreactive sites of the adjacent molecules. In the columnar mesophase, the liquid-crystalline order is disturbed by the E/Z-photoisomerization. It turns out that a highly fluid-like environment, which is present in aggregates formed in a poor solvent, is important to provide the required population of reactive sites in order to obtain a defined photocycloaddition reaction.