Cyanostilbene-based hexacatenar luminescent liquid crystals: synthesis, self-assembly and emission behavior

A series of novel hexacatenar liquid crystals incorporating two cyanostilbene units was synthesized via Suzuki coupling and Knoevenagel reactions. Structural characterization using polarized optical microscopy, differential scanning calorimetry, and small-angle X-ray scattering confirmed their ability to self-assemble into a rectangular columnar mesophase. The self-assembly of these compounds was demonstrated through molecular dynamics simulations. These compounds exhibited aggregation-induced emission behavior alongside weak solvatochromism, attributed to their twisted molecular conformations and poorly separated frontier orbitals. Notably, the hexacatenars displayed thermochromic properties, manifesting as a hypsochromic shift and fluorescence quenching upon heating, which correlated with phase transitions and enhanced molecular planarization. Density functional theory calculations substantiated the proposed mechanism governing the emission behavior. Collectively, this work establishes a rational molecular design strategy for the development of hexacatenar luminescent liquid crystals with considerable application potential.