Stable planar chirality of arylated pillar[6]arene and its thermal response

Abstract

Macrocyclic molecules with chirality have been studied because of their wide applications in the field of chiral recognition, chiroptical materials, and asymmetric catalysis. Planar chirality of pillar[n]arenes also contributes to many applications. Without bulky substituents, racemization occurs between pillar[n]arene enantiomers. Pillar[5]arenes with stable planar chirality have been formed by introducing bulky substituents into the pillar[5]arene rims. However, pillar[6]arene enantiomers that show stable planar chirality by introducing bulky conjugated moieties have not been reported. Herein, we report stable planar chirality of pillar[6]arene by introducing biphenyl groups into one benzene unit of pillar[6]arene. The enantiomers show thermo-responsive circular dichroism signals without racemization.