Modulating Energy Transfer and Light‐Emitting Colors by Chiral Dye Exchange and Achiral‐to‐Chiral Dye Conversion

Abstract

AbstractNew chiral and achiral dyes were synthesized by using clean, highly efficient Diels–Alder ‘click’ reactions. We prepared pure endo‐ and exo‐ stereoisomers and blue‐light‐emitting single crystal of an exo‐isomer. 1H NMR spectroscopy and single‐crystal X‐ray diffraction reveal the precise spatial configurations of endo‐ and exo‐dye stereoisomers. Single‐crystal X‐ray diffraction results reveal the dynamic nature of Diels–Alder covalent bonds. By reversible formation and cleavage of dynamic covalent bonds, an achiral dye was converted to a chiral dye, where achiral dansyl dye moiety was replaced by chiral moiety. Before achiral‐to‐chiral dye conversion, the dye system displayed dansyl acceptor green light‐emitting color due to intramolecular fluorescence resonance energy transfer, where the blue emission of pyrene donor fluorophore was not observed. After achiral‐to‐chiral dye conversion, light‐emitting colors of dye system change from green to blue, where the pyrene‐to‐dansyl fluorophore energy transfer was suppressed, and pyrene fluorophore blue emission was restored. Chiral transfer occurs in a chiral dye solid from non‐chromophore alky chirality to pyrene chromophore. Thus, the chiral dye solid displayed chiral optical behaviors, i. e., circular dichroism and circularly polarized luminescence.