Highly ordered smectic phases from polar calix[4]arene derivatives

A novel series of highly luminescent end-functionalized tetra-oligophenylene substituted calix[4]-arenes have been synthesized by palladium-catalyzed Suzuki cross-coupling of arylboronic acid and tetraiodocalix[4]arene as a key step. It is important to find that liquid crystallinity can easy be induced by introducing the polarity or enhancing the polarizability of the three-dimensional phenylene-substituted calix[4]arene rigid segment. In contrast to the classical one-dimensional 4-cyano-4′- alkoxybiphenyl mesogens, which exhibit nematic and/or smectic A phases, cyano-phenyl-calix[4]arene and methyl-biphenyl-calix[4]arene derivatives exhibit highly ordered smectic supramolecular organization as evidenced by the polarized optical microscopy and X-ray diffraction studies. On the basis of the results of X-ray diffraction, an interdigitated antiparallel packing mode is proposed for the ordered smectic mesophase. The presence of the strong dipoles in the rigid calixarene segments not only facilitates and stabilizes the formation of the highly ordered lamellar smectic structure but also enhances the optical properties of calix[4]arene derivatives. Our findings provide a new guideline to design interesting three-dimensional luminescent mesogenic materials.