One Molecular Probe with Opposite Enantioselective Fluorescence Enhancement at Two Distinct Emissions

It is discovered that one enantiomer of a chiral substrate can greatly enhance the fluorescence of one molecular probe at one emitting signal (λ₁ = 517 nm), while the opposite enantiomer of the substrate greatly enhances the fluorescence of the same probe at a distinctively different emission (λ₂ = 575 nm). This probe is made of a 1,1'-binaphthyl-based chiral dialdehyde that in combination with Zn²⁺ under slightly acidic conditions shows a chemoselective and enantioselective fluorescent response to histidine. The opposite enantioselective fluorescent responses of the probe at two emissions allow it to be used to determine both the concentration and the enantiomeric composition of the substrate using a single probe. The mechanistic study has revealed two very different reaction pathways when the two enantiomers of the substrate are treated with the probe. These reaction pathways generate two different products, one dimeric and another polymeric, with very different emissions.