Chiroptical Switch Based on Photoisomerization of Bilirubin-Ⅲα Bound to Human Serum Albumin

摘要

Feringa and co-workers recently described the first chiroptical molecular switch. Their system was based on rapid reversible photochemical interconversion of two helical, intrinsically chiral, alkene diastereomers with opposite helicities. Different wavelengths of UV light were used to interconvert photostationary mixtures of the two chiral diastereomers, and the interconver-sions were detected by circular dichroism (CD) spectroscopy. We describe here another chiroptical switch, based on an analogous yet different principle, which is sensitive to visible light. In this system, light is used to interconvert two diastereomers of a bichromophoric complex in which the relative orientation and proximity of the two conjoined chromophores results in strong exciton coupling and large chiroptical effects. Interconversion between the two diastereomers is manifested by substantial changes in CD absorption.