Control on Dimensions and Supramolecular Chirality of Self-Assemblies through Light and Metal Ions

Precise
control over helical chirality and dimensions of molecular
self-assemblies, a remaining challenge for both chemists and materials
scientists, is the key to manipulate the property and performance
of supramolecular materials. Herein, we report that a cholesterol-azopyridine
conjugate could self-assemble into organogels with photocontrollable
dimensional transition from 2D microbelts to 1D nanotubes and finally
to 0D nanoparticles. The E/Z-Photoisomerization
of the 4-azopyridine unit is the major driving force for the dimensional
transformation. Furthermore, the self-assembled structures were observed
to exhibit metal ion-mediated helicity inversion through the metal
coordination. These observations were collectively confirmed by several
techniques including scanning electron microscopy, atomic force microscopy,
circular dichroism, and X-ray crystallography. The rational design
of building blocks for the construction of dimension and chirality
controllable self-assembly systems may lead to versatile applications
in smart display, advanced optoelectronic device, and supramolecular
asymmetric catalysis.