Chiral versus Achiral Assemblies in Multi-Stimuli Responsive Supramolecular Polymerization of Tetra-Substituted Azobenzene Dye.

Incorporating photoswitchable moieties into the molecular design of supramolecular architectures provides unique opportunities for controlling their morphology and functionality via optical stimuli. Harnessing geometrical and electrical changes in response to multiple external stimuli on the molecular level to modulate properties remains a fundamental challenge. Herein, the reversible formation of the aggregates of l-tyrosine E-azobenzene-tetracarboxamide (E-ABT) is shown to be finely controlled by light, solvent, or chemical additives. The resulting products differ not only in their overall morphology and supramolecular interactions, but also in their intrinsic chirality, that is, depending on the conditions applied, self-assembly yields chiral columns or π-stacked "achiral" oligomers. This report shows the potential of rational monomer design to achieve controlled self-assembly by stimuli of choice and paves the way toward the use of multi-responsive, sterically hindered azo-benzene aggregates in materials chemistry and nanotechnology.