The Self-assembly And Regulation Of Supramolecular Chirality Based On The Amphiphilic Glutamide Azobenzene

Supramolecular gels have shown great application prospects in many fields such as intelligent response materials,biomedicine,chiral recognition and reaction catalysis.Supramolecular chirality refers to the asymmetric packing of the building blocks by the weak interaction of non-covalent bonds and exhibit chiral signals（CD signals）under certain conditions.The supramolecular chirality is easy to regulate by external stimuli（such as light,solvents,p H,temperature,ultrasound,redox,etc.）.In recent years,due to the advantages of non-contact,non-invasive,clean and controllable wavelength of light,the regulation of supramolecular chirality by light has aroused the interest of scientific researchers.In this paper,using the photoisomeric characteristics of azobenzene,the amphiphilic azobenzene with chirality center glutamic acid is designed and synthesized.Firstly,we study its gelation ability and photoresponse characteristics in different solvents,secondly we study the regulation of light on the assembly and light,solvent on supramolecular chirality regulation and corresponding functionalization research,the specific research content is as follows:1)A supramolecular gel based on azobenzene glutamine amphiphilic（GAZS）was prepared,and its structure was characterized by NMR and mass spectrometry.GAZS shows different CD signals in different solvents,regulating solvent polarity can regulate supramolecular chirality,and GAZS can also specifically identify methanol solvents in alcohol solvents.GAZS becomes a swelled gel after UV irradiation in methanol,and the CD signal disappears,and the gel recovers and displays the CD signal after heating.The microscopic morphology was studied,and it was found that when the nanostructure of the assembly was formed from a monolayer structure,the helix or chirality of the nano/microstructure was consistent with the helicity displayed by the CD signal.The selective enantiomeric release performance of gels was tested by high performance liquid chromatography.This part of the experiment not only provides ideas for the regulation of supramolecular chirality by external environment regulation,but also provides a new way for selective enantiomer release.2)The azobenzene-glutamine amphiphilic gelator C₄Azo Glu was prepared,which can form hydrogels in water and host-guest complexes withα-Cy D in water.Testing the circular dichroic signal of C₄Azo Glu in the single-molecule state and the aggregated state,it was found that chiral molecular self-assembly can produce supramolecular chirality,which is determined by molecular chirality.In the single-molecule state in aqueous solution,the chirality of the C₄Azo Glu?α-Cy D complex is determined byα-Cy D,while in the hydrogel state,the supramolecular chirality is determined by the molecular chirality of the gelator.Since the cavity ofα-Cy D promotes isomerization of azobenzene,the C₄Azo Glu?α-Cy D assembly irradiated by ultraviolet light has a weaker signal than the original C₄Azo Glu?α-Cy D hydrogel,and the supramolecular chiral optical switch can be realized by trans-cis isomerization under UV irradiation and heat.Through the host-guest strategy,C₄Azo Glu?α-Cy D hydrogel can not only achieve CD signal change under ultraviolet irradiation.Moreover,the morphological transformation of nanofibers to nanosheets and the phase transition of gels to sols can be realized.This part of the experiment can provide some insights for the regulation of supramolecular chirality and nanostructure,and has potential application value in intelligent chiral devices.3)Several azobenzene-based amphiphilic molecules with different alkyl chain lengths were designed and synthesized.Amphiphilic molecules self-assemble in water and display CD signals.Alkyl chain length plays a significant role in self-assembly and corresponding chiral optical properties.While long alkyl chains can promote gelation capacity and enhance supramolecular chirality,the hydrophobic interaction of alkyl chains conversely increases theπ-πaccumulation of azobenzene,limiting isomerization of the azobenzene moiety.Alkyl chain lengths of amphiphilic molecules,as well as external stimuli,can have some effect on self-assembling nanostructures.This work elucidates the relationship between substituent alkyl chain groups and self-assembled CD signals,providing insights into the design of functional smart chiral materials.