Bent-core hexacatenar liquid crystals with diphenylmethane or benzophenone core and salicylaldimine arms: Self-assembly and dual-modality fluorescence probe

This study investigates two novel bent-core salicylaldimine hexacatenar liquid crystals, SDM and SBP, focusing on their self-assembly modes and multifunctionality, which are modulated through the structural differentiation of their central cores. The diphenylmethane core in SDM enables the formation of a rectangular columnar phase (Col_rec/p2mm) through tilted stacking of dimer formed by two molecules, while SBP with a benzophenone core, forms a highly symmetric square columnar phase (Col_squ/p4mm) with a broader liquid crystal phase range and enhanced thermal stability due to the strong polarity and dipole-dipole interactions between molecules. Moreover, SDM and SBP can form organogels in N, N-dimethylformamide (DMF) and n-hexane, respectively. Photophysical investigations reveal that both compounds exhibit characteristics of excited state intramolecular proton transfer (ESIPT), significant Stokes shifts, and aggregation-induced emission (AIE) effects. Furthermore, SDM can serve as a dual-channel fluorescent probe that enables and simultaneous recognition of Cu²⁺ and Zn²⁺ to achieve an “on-off” dual-modality response, overcoming the limitations of traditional Schiff base-based single-ion probes.