Spontaneous Chirality Induction and Enantiomer Separation in Liquid Crystals Composed of Achiral Rod-Shaped 4-Arylbenzoate Esters

Abstract

The discovery of spontaneously induced chirality and enantiomeric separation in liquid crystal and soft crystal systems composed of achiral rod-shaped 4-arylbenzoate esters is described. Negligibly small circular dichroism (CD) signals are produced in the smectic A (SmA) phases of these substances, and the signals were found to increase with increasing smectic order. Since the advent of chirality occurs in freely suspended films, it is not a consequence of surface effects. Both positive and negative CD signals are observed with equal probability at different positions in these films. Vibrational CD spectroscopy and theoretical calculations are used to analyze the conformational changes that are associated with the induced chirality of the rod-shaped molecules. The results show that the phenomenon is caused by the twisting of biphenyl bond associated with the ester moiety in 4-arylbenzoate esters.