Helical tube triggered two-stage emission behavior for tetraphenylethene-functionalised hemicyanine dye: Better dispersion stronger fluorescence

Helix Induction and Inversion of Polymeric Foldamer Regulated by the Single Enantiomers

In general, a single enantiomer can induce a foldamer into a preferred-handed helix, while another condition is required for the helical inversion. In this work, it is found that the helix induction and subsequent inversion of the poly(m-phenylene diethynylene)-based foldamer bearing aza-18-crown-6 pendants (Poly-1) can be realized by increasing the concentration of sterically hindered L-amino acid perchlorate salts. When the amount of chiral enantiomers is small, one enantiomer tends to complex with two non-adjacent aza-18-crown-6 rings via three N⁺ -H···O hydrogen bonds in a sandwich mode. Notably, the transition dipole moment is perpendicular to aza-18-crown-6 ring, so that the induced helical chirality in Poly-1 main chain is opposite to the chirality of enantiomers. When the amount of chiral enantiomers is large enough, each aza-18-crown-6 is occupied by one enantiomer, which causes the transition dipole moment in a parallel direction to aza-18-crown-6 ring. In this case, the increased steric hindrance can facilitate the inversion of screw sense of Poly-1 main chain, which is directed by chiral center of enantiomers. As a result, a helix inversion has been achieved successfully. This work not only provides a novel strategy for regulating the two-stage folded helical conformations by the single enantiomers, but opens a window to develop chiral recognition materials. This article is protected by copyright. All rights reserved.

Thermotropic chirality enhancement of nanoparticles constructed from foldamer/bis(amino acid) complexes

Herein, chiral nanoparticles are constructed by mixing an artificial foldamer bearing aza-18-crown-6 pendants with l-homocystine perchlorate salt, showing a thermotropic chirality enhancement due to the binding mode changes in the heating process.