High hole mobility and light-harvesting in discotic nematic dendrimers prepared via "click' chemistry

We report a new family of liquid crystalline porphyrin-core dendrimers with coumarin units at the periphery of the dendrimer. These compounds have been prepared by copper-catalyzed azide-alkyne click cycloaddition (CuAAC). The mesomorphic properties have been investigated via polarized optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The peripheral coumarin units play a key role in the liquid crystal behavior, contributing to the appearance of discotic nematic mesophases with hole mobility values among the highest values reported for discotic liquid crystals (of the order of 1 cm(2) V-1 s(-1)). It has also been demonstrated that excitation of the coumarin moieties leads to energy transfer (antenna effect) to the luminescent porphyrin core. Therefore, this strategy, which involves click' chemistry, has been proven to be a powerful and elegant synthetic tool for the preparation of optoelectronic materials based on complex dendritic architectures.