Construction And Properties Of Emissive Metallo- Supramolecular System Based On Tetraphenylethylene

During past few years,the metallo-supramolecular luminescent materials have attracted considerable attention due to their wide applications including chemical/biosensors,bioimaging and optical devices,etc.Therefore,the development of novel luminescent metallo-supramolecular systems has been one of the major driving forces for supramolecular chemists.Encouraged by the power and versatility of coordination-driven self-assembly,various metallo-supramolecular light-emitting architectures were constructed efficiently.Hitherto,tetraphenylethylene(TPE)as an well-known chromophore has been broadly anchored to metal receptors to endow emissive architectures aggregation-induced emission(AIE)property.Most these AIEtype metallo-organic supramolecules display intense emission under aggregate state.However,no emission or a weak emission can be observed in solution.With the aim to build luminescent system in both dilute solutions and aggregation state,we presented the introduction of the restriction of intramolecular motions(RIMs)through coordination and immobilization within rigid frameworks.This dissertation includes the following main contents as shown below:Chapter one,summarizes the development of coordination-driven self-assembly,supramolecular metallo-organic luminescent materials,especially TPE-related lightemitting metallo-organic system as well as introduction of RIMs through different strategies.The projects of this dissertation are proposed at the end of this chapter.Chapter two,focuses on the design and synthesis of AIE active supramolecular macrocycles with free dangling phenyl rings in the TPE core.Owing to the soft skeleton of TPE unit and different binding sites in the TPE-TPY ligands,dimer,tetramer,hexamer were assembled via coordination-driven self-assembly.All these three macrocycles exhibited typical AIE phenomena.The emission intensity and quantum yields were increased with gradually increasing water fraction.Futhermore,transmission electron microscopy(TEM)was utilized to investigate the aggregate behavior of these macrocycles during AIE process.Interestingly,as detected by TEM,the well-defined dimer and hexamer formed nanotube bundles via hierarchical selfassembly in the mixture of acetonitrile and water.Chapter three,three generations of TPE-TPY ligands were designed and synthesized to construct luminescent rosettes.The intramolecular motions of TPE in ligands were partially restricted even in dilute solution,thus leading to fluoresce in both dilute solution and molecular aggregation states.In addition,TPE-TPY ligands were assembled with Cd(II)to introduce additional RIMs and immobilize TPE fluorophores into rosette-like metallo-supramolecules.More importantly,the fluorescent behavior of TPE-TPY ligands is preserved in these rosettes,which exhibit tunable visible-light emissive properties with respect to different generations.Particularly,the second generation of rosette emit pure white light.As expected,the quantum yields of rosettes in solution displayed remarkable increment with increasing binding sites.To gain deep insights into the emissive behavior of these rosettes,TEM,AFM and DLS experiments were employed to investigate the size and aggregate behaviors.Chapter four,a highly RIMs system based on four-armed TPE-pyridinium salts was designed and synthesized.The highly RIMs effect of TPE leads to emission not only in dilute solution but also aggregation states.Furthermore,we anchored the bulky TPY substituents to four-armed pyridinium salts to introduce more RIMs and selfassembly.Interestingly,the TPE-TPY pyridinium ligand was assembled with Zn(II)to construct supramolecular triangular prism with tunable emissive properties.Compared with model compound,the luminescent intensity of supramolecular triangular prism was increased by 2-fold.More importantly,circular dichroism(CD)experiments revealed that the chirality of TPE-pyridinium salts and supramolecular triangular prism could be induced by chiral anion.Chapter five,a feasible strategy was established to expand the scope of metallosupramolecular polymer with helical architecture as well as strong emission property.The construction of metallo-helicoid was combining covalent polymerization and coordination-driven self-assembly stepwisely.To our interest,the coordination triggered the assembly of linearly organic polymer backbone preferentially adopting a right-or a left-handed conformation with double rims.Furthermore,a single or double-stranded DNA molecule(ssDNA or dsDNA)was encapsulated within the channel of the metallo-helicoid through multiple electrostatic interactions.The encapsulation of DNA molecule leads to the enhancement of luminescent intensity of metallo-helicoid due to the RIMs mechanism.Moreover,the chirality of metallohelicoid was induced by dsDNA as detected by CD.