Chiral Reticular Self-assembly Strategy To Construct Efficient And Tunable Circularly Polarized Luminescent Materials

Circularly polarized luminescence(CPL)refers to the differential emission of left and right circularly polarized light from chiral systems while excited by unpolarized light.CPL is of great significance in understanding the excited-state chirality and developing advanced chiroptical materials.Since its potentially photonic applications in true 3D display,circularly polarized light emitting devices(CP-LEDs),high-density information storage and encryption,advanced biological probes and optoelectronic devices,the fabrications of CPL materials have been obtained great interests in the field of photonic materials.In this thesis,we proposed the chiral reticular strategies to design and fabricate CPL materials with reversible regulation,overall improvement and continuous tuning of CPL colors.Our achievements were as follows:In the first part,we successfully constructed optically pure metal-organic frameworks through a chiral reticular self-assembly strategy by combining an achiral aggregation-induced luminophore(AIEgen)and chiral donors(D/L-Cam,camphoric acid)via a metal ion bridge(Cd(II)).It is found that the framework enabled emission(FEE)from isolated AIEgens.Meanwhile,the chiral donors induced the achiral AIEgen to stack into helical manner through space chirality transfer(TSCT)in the framework.Consequently,the whole MOF exhibited strong CPL activity.Remarkably,under ultrasonication and grinding,the local and global structural changes of the framework were achieved along with respectively blue-and red-shift CPL for the first time.Such dual mechano-switchable CPL is totally reversible.This work provided not only offered a feasible and versatile strategy for color-regulated solid-state CPL materials,but also obtained new knowledge on AIE rotors.See Chapter 2 for the detail.In the second part,we proposed a new strategy to improve the overall CPL performance by designing self-confined helical macrocycles.We linked luminescent pyrene with chiral trans-1,2-cyclohexanediamine(c HDAm)via dynamic covalent bonds to obtain triangles T1 and T2.At molecular states,T1 and T2 exhibited strong CPL activity and high luminescence quantum yield(QY,up to 80%)due to the effective self-confinement.In aggregates,T1 and T2 also displayed high QY and amplified CPL activities due to the steric self-isolation effect of helical macrocycle.Both the molecules and aggregates showed environment tolerant colors in different solvents.That is,self-confined helical macrocycle was a feasible strategy for comprehensive CPL performance improvement.Remarkably,the zigzag-shaped pyrene unit endowed T1 with planar chirality(conformation),which results in completely opposite helical fibers and CPL in solvents with different polarity.By contrast,the linear T2 has no planar chirality with the entirely chirality was controlled by the point chirality of c HDAm(configuration).This work witnessed that the self-confined helical macrocycles would be promising in the design of robust chiroptical materials both in molecular states and aggregates and provided an insightful understanding of supramolecular chirality and self-assembly of chiral macrocyclic molecules.See Chapter 3 for the detail.In the third part,we designed an abnormal AIE cage,which was synthesized from C3-symmetric molecule(TPA)as prism surfaces and chiral c HDAm derivertive as edges.In such highly twisted prism,the helical angle is 60 ° and the phenyl rings were unconfined either in the molecular state or the aggregates.Therefore,the cage showed abnormal AIE properties with no luminescence in both molecular and aggregation states.We supposed that the cage would be lighted up if the additional steric hindrance was introduced.To this purpose,an aromatic boron(TFPB)was selected in view of the Lewis acid-base coordination of boron and nitrogen atoms.It worked and the aggregates of the cage/TFPB composite showed strong CPL with the color further continuously regulated through the changing of the ratios of cage/TFPB.This work provided new knowledges on AIE phenominum and the design of tunable CPL materials.See Chapter 4 for the detail.In summary,the thesis introduced the strategies of chiral reticular self-assembly from MOF to small organic frameworks,then focused on the challenges in the fabrication of CPL materials.The works provided a new platform for rational designs,mechanistic insights and performance regulations on CPL materials.