Control On Supramolecular Chirality And Circularly Polarized Luminescence Of Supramolecular Gels By Achiral Luminophores

Circularly polarized luminescence（CPL）is defined as the difference between the emission of left（L）-and right（R）-handed circularly polarized light observed for a nonracemic chiral system after photoexcitation with nonpolarized light.Recently,CPL-active functional materials have been attracting growing attentions thanks to their promising applications in quantum storage,optical sensors,photoelectric devices and asymmetric photocatalysis.Searching for efficient approaches for obtaining CPL-active materials with adjustable chirality and high luminescence dissymmetry factor(g_lum)is important.Supramolecular assembly based on the rational design of chiral units and fluorophore molecules through non-covalent interaction provides a simple and powerful tool to construct CPL materials with high activities.Supramolecular chirality in nonemissive systems has been controlled by changing external achiral factors,which provides enlightenment to regulate the chirality of CPL through controllable self-assembly based on non-covalent interactions.In this thesis,we presented a simple and universal strategy for the preparation of chiroptical supramolecular gels with high g_lum values and controllable supramolecular chirality and CPL.Chiral phenylalanine derivatives and achiral coumarin derivatives are used as the building blocks to construct chiroptical supramolecular gels based on highly ordered supramolecular assembly processes.The potential applications of CPL-active supramolecular gels in circularly polarized light-emitting diodes and circularly polarized light detection are further explored.The contents of the thesis are as follows:1.A co-assembled supramolecular CPL system composed of chiral phenylalanine derivatives（LPF and DPF）and achiral naphthylamine isomers with amine groups at theαandβ-position（1NA and 2NA respectively）is employed.The co-assembled hydrogels displayed significant CPL performance and the strongest CPL intensity is obtained in LPF-1NA and LPF-2NA systems.Typically,the handedness of CPL of cohydrogels could be inverted by varying the achiral isomers.The different hydrogen bonds andπ–πstacking interactions are vital factors for the inversion of CPL.This work realized the inversion of CPL,which not only contributes to an understanding of the relationship between inherent molecular chirality and supramolecular chirality,but also presents an alternative method to construct tunable CPL-active materials.2.Nanotwisted fibers exhibiting strong full-color and white CPL with high g_lum values are obtained by co-assembing chiral phenylalanine derived gelators（LPF and DPF）and achiral commercial aromatic molecules（Pym,2An,1An,and RB）.The synergic effect ofπ–πstacking interactions and hydrogen bonding between the chiral gelators and achiral molecules resulted in ordered co-assemblies,enabling the chirality of the gelators to be highly efficiently transmitted to the achiral molecules,leading to the formation of supramolecular gels with high g_lum values.In particular,supramloecular nanoassemblies with white CPL can be achieved by tuning the ratio of colorful aromatic molecules in the gel.Furthermore,we studied the performance of these CPL-active nanoassemblies in circularly polarized light emitting devices.3.To transfer the supramolecular chirality to inorganic systems,chiral helical supramolecular hydrogels with controllable helical pitch and diameter were obtained by positively charged achiral carbon dots co-assembled with negatively charged chiral phenylalanine derivatives.The co-assembled hydrogels showed both circular dichroism（CD）and CPL signals in the absorption regions.The supramolecular hybrid hydrogels membrane with the highest g_lum value,which are able to efficiently differentiate between left and right circularly polarized light.4.Chiral additives（L-MH or D-MH）induced achiral coumarin derivatives（PyC）to procedure chiroptical supramolecular gels through hydrogen bondings between pyridine and hydroxyl groups.PyC and L-MH（D-MH）can coassemble into chiral nanostructures,and the handedness of these nanostructures was dictated by the chirality of the hydroxyl alcohol.The formed coassemblies show chiroptical activity,including CD and CPL via efficient chiral transformation.In addition,the resulting coassemblies remained chiroptical activity even after the removal of the chiral hydroxyl alcohol.Typically,the removed chiral hydroxyl alcohol can be reused for further coassembly to achieve continuous generation of supramolecular chirality.This study presents a chiral supramolecular auxiliary approach for manufacturing chiroptical nanostructures exhibiting chiral induction,transference,amplification,and memory process.