Chiroptical Properties of Glucose-Substituted Poly(p-phenylene-ethynylene)s in Solution and Aggregate State

The aggregation behavior of two D-glucose-substituted phenyleneethynylenes, an alternate copolymer (AP) and a homooligomer (HO), has been investigated by means of UV-vis absorption, circular dichroism (CD) and fluorescence spectroscopy. CD reveals superior capability to detect the early stages of aggregation and to provide information about aggregate geometries. The multiband CD spectrum of the AP and of analogous chiral PPEs is rationalized on the basis of the exciton coupling between vibronic transitions localized on proximate portions of the chromophoric chains.