A new cyclodextrin–polythiophene conjugate (CDPT) has been prepared by attaching permethyl-α-cyclodextrins to polythiophene (PT) through a hexamethylene tether. Circular dichroism spectral examination of CDPT revealed that only a weak positive Cotton effect (Δε=0.1 M⁻¹ cm⁻¹) was induced at the main band of the PT in dimethyl sulfoxide and similarly weak bisignate signals in pure and aqueous methanol solutions, which indicates that the α-cyclodextrins appended to PT with a long tether are ineffective in inducing a homochiral structure in the PT backbone. Nevertheless, enantiomeric amino acids and dipeptides added to an aqueous methanolic solution of CDPT caused chirality-dependent hypochromic changes in the UV/Vis spectra, which enabled us to sense these species and quantitatively determine the enantioselectivity by observing the difference in absorbance upon interaction with pairs of enantiomers. Enantiomeric d,d/l,l-dipeptide pairs rather than D/L-amino acid pairs were better differentiated in general, the highest dd/ll selectivity of 13.7 being observed for Phe-Phe.

An enantiomeric binaphthyl unit was tethered to adjacent thiophenes with oxyethylene linkers to give a chiral polythiophene with binaphthocrown ether cavities. Upon inclusion of a chiral cationic guest in the cavity of the chiral crown ether–polythiophene conjugate, the bithiophene unit was twisted to shorten the effective conjugation length of polythiophene backbone, enabling us to sense the guest binding by reading out the amplified optical signal gains arising from the backbone structure change. This strategy allowed us to discriminate the guest chirality without using chiroptical signals or a circular dichroism spectrometer to achieve the highest enantioselectivity of 7.3 for valine methyl ester with a 40-fold enhanced sensitivity compared with the corresponding monomeric sensor.