Molecular Insights into Supramolecular Self-Assembly of Chiral BODIPYs toward Enhanced Chiral Optical Activity

Abstract

Chiroptically active molecular materials exhibiting enhanced excitonic couplings are refreshing for organic–inorganic hybrids, molecular nanophotonics, and many other fields. Here, we synthesized multiple chiral derivatives of boron dipyrromethene (BODIPY) substituted with 1,1′-binaphthyl-2,2′-diol (BINOL). Different aromatic groups in terms of number and position were designed on the BODIPY skeleton to finely tune their supramolecular self-assembling behaviors. It was found that the chiral derivative with an anthracene group at position 8 of the BODIPY skeleton formed a helical nanofiber showing markedly sharp spectra of both absorption and circular dichroism. Intermolecular excitonic couplings lead to a significantly improved dissymmetry factor of circular dichroism and circularly polarized luminescence. Different π–π stacking interactions between the molecular components were revealed through systematic molecular designing and theoretical studies, providing insights into the self-assembling mechanism of these building blocks. These results shed light on new molecular materials development for a variety of chiral excitonic/plasmonic and optoelectronic applications.