Self-Assembly of Urea-Connected Pyrene-Glutamate Conjugate: Linker and Fluoride Ions Modulated Circularly Polarized...

Here, we report the synergistic modulation of circularly polarized luminescence (CPL) achieved through the integration of a flexible linker and a fluoride-responsive urea unit. Two pyrene-conjugated chiral building blocks, PUG and its flexible-linked analogue PMUG, were designed and synthesized, incorporating glutamate as the chiral unit, urea bonds as the ion-responsive site, and pyrene as the luminophore. In their molecular state, neither circular dichroism nor CPL signals were detectable. Upon assembly, both PUG^Agg and PMUG^Agg adopted lamellar stacking arrangements and exhibited excimer emission. Remarkably, the introduction of the methylene linker led to opposite CPL handedness between PUG^Agg and PMUG^Agg. Upon the addition of fluoride ions during assembly, the morphology of PUG/F^-Agg transformed from fibers to ribbons, accompanied by an inversion and reduction of the luminescence dissymmetry factor (g_lum) from -5.9 × 10^-3 to 0.8 × 10^-3. In contrast, PMUG/F^-Agg assemblies evolved from sheets to multistranded fibers upon fluoride treatment, resulting in a significant enhancement of g_lum from 2.6 × 10^-3 to 9.0 × 10^-3. Mechanistic investigations revealed that while the flexible linker finely modulates molecular packing conformations, fluoride ions competitively disrupt intermolecular hydrogen bonds and reprogram the assembly driving forces. This synergistic regulation strategy offers a novel platform for the development of multiresponsive chiroptical materials.