Light-Induced Folding of Azobenzene Derivatives with Axial Chirality and Chirality Inversion

Understanding of photoisomerism effect on the chiral transportation occurred intra- and intermolecularly shall facilitates the fabrication of smart chiroptical materials for sensing, recognition, and display. Here we present the photoisomerization-enabled molecular folding and chirality transportation. Azobenzene core is conjugated with two chiral arms comprising of amino acid segments. The substituted position including ortho- and para-positioned substituents affects the formation of intramolecular interactions, leading to distinct adaptiveness toward the solvent media. The trans-cis isomerism of azobenzene allows for the reversible manipulation of chiroptical properties, accompanied by the appearance of axial chirality. The ortho-substituted azobenzene can form folded structures stabilized by intramolecular CH-π interactions in trans-form, while in the cis-form, the conformation is stabilized by the hydrogen bonds between the oxygen atom and the hydrogen attached to the nitrogen in the amide segment. Structural transformations induced by solvent and light irradiation were revealed through density-functional theory (DFT)-based computational studies and experimental results. This work unveils the photoisomerization effect on folding, and achieves reversible conformational changes and chirality inversion, showing potential for constructing advanced smart chiroptical materials.