Investigation of supramolecular architectures of bent-shaped pyridine derivatives: from a three-ring crystalline compound towards five-ring mesogens

Abstract

In search of novel photoactive liquid crystals, we have synthesized a series of five-ring pyridine-based bent-core compounds bearing different substituents at the peripheral phenyl rings (CH₃O, Cl and NO₂). Their mesomorphic behaviour has been investigated by polarizing optical microscopy, differential scanning calorimetry and X-ray scattering, and then compared with the unsubstituted parent compound. The introduction of the methoxy groups at the peripheral phenyl rings of the bent core results in a non-mesomorphic compound, whereas the chloro- and nitro-substituted compounds form enantiotropic B1-like phases. Significant changes in the textures and transition temperatures of the mesophase have been observed under UV light. The present investigation of the mesomorphic properties of the synthesized compounds, coupled with the analysis of the molecular packing of the related three-ring compounds, will help design self-organized molecules suitable for UV indicators.