Remote optical chirality transfer via helical polyaromatic capsules upon encapsulation

Abstract

Helical molecular assemblies have been widely created so far, taking inspiration from helical bioconstructs (e.g., DNAs and proteins). However, the host utilities of such synthetic helices remain largely underdeveloped, particularly as chiroptical nanotools. Here, we report the preparation of new polyaromatic capsules with right- or left-handed quadruple helicity, regulated by chiral saccharide-based side chains attached at the outer surface. The capsule quantitatively encapsulates achiral fluorescent dyes in the cavity. The resultant host-guest complexes display excellent circularly polarized luminescence properties (up to | g lum | = 1.6 × 10 −2 ) derived from the bound dyes, through efficient optical chirality transfer from the outer biochiral groups to the inner achiral dyes via the quadruple helical shell, which represents an unprecedented chiroptical strategy. This nanotool can be applied to spherical fullerene to induce its chirality with high efficiency in solution (up to | g abs | = 1.0 × 10 −2 ) and in the solid state. • Preparation of new capsules, bearing saccharide chains, with regulated helicity • Observation of chirality transfer from the chains to fluorescent dyes in the cavity • Demonstration of host-to-guest remote chirality transfer toward fullerene dye Helicity is one of the most important biological motifs. Whereas artificial helical assemblies have been widely prepared, the utilization of the inner spaces within the frameworks remains largely underdeveloped so far. Here, we introduce new polyaromatic capsules with right- or left-handed quadruple helicity, regulated by chiral saccharide-based side chains. The capsule encapsulates achiral fluorescent and fullerene dyes in the well-defined cavity. The resultant host-guest complexes display excellent circularly polarized luminescence (CPL) and strong induced circular dichroism (CD) properties, respectively. The observed remote optical chirality transfer from the outer biochiral groups to the inner dyes via the helices represents an unprecedented chiroptical strategy, which will lead to the new development of superior helical tools for chiral biosensing and asymmetric synthesis. Taking inspiration from helical bioconstructs, new polyaromatic capsules with right- or left-handed quadruple helicity were prepared by simply attaching chiral saccharide-based side chains to the exterior. Upon encapsulation of fluorescent and fullerene dyes, remote chirality transfer from the biochiral groups to the bound achiral dyes was demonstrated with excellent efficiency. The present helical capsules will act as novel chiroptical nanotools for the development of superior chiral biosensing and asymmetric synthesis.

Topics & Concepts