Self-Assembled Dansyl-Based Chiroptical L/D-Valine and L/D-Phenylalanine Conjugate for Hg(II) Detection and Catalytic Conversion of Carbon Dioxide.

Abstract

Rational design and synthesis of a new class of self-assembled, dansyl-functionalized chiral conjugates derived from L/D-valine and L/D-phenylalanine are independently utilized for applications in selective Hg(II) sensing and catalytic CO₂ conversion. The enantiomeric systems (1-L/D and 2-L/D) obtained via sulfonamide coupling with dansyl chloride were fully characterized by advanced spectroscopic methods and single-crystal X-ray diffraction. Circular dichroism confirms efficient transfer of chirality from the amino acid backbone to the supramolecular assemblies. At the same time, atomic force microscopy reveals distinct stereochemical control: L-forms generate nanospherical structures, while D-forms produce nanoconical morphologies. The conjugates exhibit strong dansyl-based fluorescence with highly selective turn-off responses toward Hg(II), following Stern-Volmer behavior with micromolar detection limits; Job's plot and morphology variations support metal-induced reorganization. Independently, they function as hydrogen bond donor organocatalysts for solvent-free CO₂ cycloaddition to epoxides, affording up to 93% conversion under mild conditions within 6 h in the presence of n-Bu₄NBr. The phenylalanine-derived system exhibits better selective sensing and catalytic efficiency, highlighting a bioinspired platform integrating chiral self-assembly, heavy-metal recognition, and sustainable CO₂ utilization.