Reversible Stereoselective Folding/Unfolding Fueled by the Interplay of Photoisomerism and Hydrogen Bonding.

A linear molecular architecture equipped with complementary three-fold hydrogen-bonding units embedded with a photoswitchable trans-tetrafluoroazobenzene moiety was synthesized. The transto cis photoisomerism of the azobenzene unit induced drastic changes in the molecular architecture as a result of intramolecular hydrogen bonding as evidenced by NMR spectroscopy and size exclusion chromatography. A minute stereogenic element in the linear trans state enabled stereoselective folding into the cis state, thus producing a globular architecture with enhanced chiroptical property.