Hydrogen-Bonding Assisted Supramolecular Self-Assembly of Double Discotic Supermolecues

Symmetric double discotic supermolecules based on porphine (Py) and triphenylene (Tp), Py(Tp)$_{4}$, have been successfully synthesized via PyBOP-catalyzed amidization reactions. The Tp moieties had either C$_{5}$- or C$_{12}$-arms, and the spacer linking between the central Py and peripheral Tp was either C$_{6}$ or C$_{10}$. Thermal properties of these supermolecules were studied by differential scanning calorimetry, and self-assembled crystalline and/or liquid crystalline textures were confirmed by polarized optical microscopy. For samples with C$_{5}$-arms in Tp, only a crystal-melt transition was observed. X-ray diffraction (XRD) on shear-oriented samples showed that Py was crystalline and Tp formed columnar liquid crystal. For samples with C$_{12}$-arms in Tp, sequential crystal-liquid crystal-isotropic melt transitions were observed. XRD results indicated that the crystalline unit cells were orthorhombic for all samples, and amide hydrogen-bonding was responsible for their supramolecular self-assembly.