Preparation And Performance Study Of Azobenzene-based Chiral Gels Modulated By Circularly Polarized Light

Modulating self-assembling process and its nano-architecture by external stimulus have promoted broad and interesting applications in nanotechnology,electronics,tissue engineering and biomedical fields.Among these stimuli,light is considered to be remotely and accurately controlled,quickly switched and easily focused,thus has attracted great interest in the construction of photo–responsive molecules and devices.Circularly polarized light?CPL?,streams of photons with either right-or left-handed spin,which can transfer integer photonic spin to molecules,has been regarded as the possible source of chiral information in living organisms.CPL-driven absolute asymmetric?AAS?,mirror symmetry breaking?MSB?,as well as nanoparticles with chiral structures or helical arrangements are three main stream for the application of CPL.While the effect of CPL handedness on small molecule self-assembly is still with less exploration.Azobenzene,as the typical photo-responsive chromophore,because of its unique isomerization properties,has been widely used in the construction of photo-responsive molecules.In general,trans-azobenzene based gelators have strong self-assembly capacities owing to their favourable planer and symmetric structures.UV-light irradiation-induced trans-to-cis transition normally will break such molecular symmetry and lead to the collapse of self-assembled structures.Interestingly,in this study,we find that the introduction of CPL with specific handedness breaks this traditional idea.For an azobenzene-based chiral gel with C_2v-symmetric structure,right-CPL promotes the collapse of gel;by contrast,left-CPL triggers the formation of a new self-assembled structure.Based on this unconventional phenomenon,a series experiments were performed to detect CPL-modulated supramolecular self-assembly for azobenzene-based chiral gel,such as UV-Vis absorption spectral,circular dichroism spectra,XRD measurements,SEM and AFM observation.Moreover,through a control experiment,the quantum chemical calculation?Gassiness?,an additional self-assembly morphologies for its corresponding enantiomer,as well as the review of related mechanism,we put forward a possible mechanism for CPL modulated self-assembly.It was the delicate balance between the isomerization of azobenzene and the chiral preference of the dipeptide that played an important role in the dissociation or supramolecular self-assembly of the azobenzene-based gelator.This unusual finding might arise great interest in the potential of CPL sources in controlling the supramolecular self-assembly of chiral molecules or polymers as well as for exploring their role in the fabrication of function materials.Moreover,our work will inspire scientists to rethink some vital chemical and biological processes from the unique perspective of“dynamic molecular chirality”.