Construction And Properties Study Of Photoluminescent Supramolecular Assemblies

In the past 30 years,coordination-driven self-assembly has evolved to be a well-established methodology for constructing supramolecular assemblies.A series of supramolecular assemblies,such as two-dimensional supramolecular metallacycles with specific shapes and complicated structures and novel three-dimensional supramolecular metallacages,have been successfully constructed.These supramolecular assemblies have displayed extensive applications in host-guest chemistry,sensing,catalysis,smart polymeric materials and biomedicines.Recently,photoluminescent supramolecular assemblies have attracted great attention due to their applications in sensing,photocatalysis,light-emitting devices,and biomedicines.Generally,there are two methodologies for constructing photoluminescent supramolecular assemblies.One methodology is the direct introduction of luminophore as the core skeleton of the supramolecular assembly.The other methodology is constructing luminescent host-guest complex by encapsulating luminescent molecules inside the cavity of the supramolecular assembly.Although fruitful achievements have been gained in the development of photoluminescent supramolecular assemblies,many problems are still far from being fully resolved in this area.For example,the heavy atom effect from from the Pt(II)-based building block sometimes induces a significant increase in the amounts of intersystem crossing(ISC),which thus leads to an obvious fluorescence quenching.Therefore,compared with their precursor building blocks,the emission quantum yields of supramolecular assemblies are relatively low,which is usually unfavorable for their practical application.Secondly,there is a relatively lack of effective and simple strategy to tune the photoluminescence properties of supramolecular assemblies,such as emission wavelength,quantum yield,and luminescence lifetime.Therefore,it is still challenging to construct supramolecular assemblies with high quantum yield,tunable emission wavelength and luminescence lifetime.This thesis mainly focuses on regulating the photoluminescence properties of supramolecular assemblies,such as the emission wavelength,quantum yield,and luminescence lifetime,and expanding the application of photoluminescent supramolecular assemblies.The research content of this thesis is mainly divided into the following chapters:In chapter one,the research progress of photoluminescent supramolecular assemblies based on coordination-driven self-assembly and their applications are introduced.Then the projects are put forward at the end of chapter.In chapter two,nine 120°triarylamine-based dipyridyl donor ligands L1–L9 with different pendant functional groups(including-CF₃,-NO₂,-CH=C(CN)₂,-CHO,-H,-CH₃,-OCH₃,-NH₂,and-N(CH₃)₂)para to the tertiary amine core were designed and synthesized,from which a series of hexagonal organoplatinum metallacycles H1–H9 with different substituents were successfully prepared through coordination-driven self-assembly.Fluorescent metallacycles with high fluorescence quantum yields and tunable fluorescence wavelengths were obtained through simple regulation of their photoinduced electron transfer(PET)and intramolecular charge transfer(ICT)properties.Moreover,3D fluorescent films and fluorescent inks for inkjet printing were fabricated using these metallacycles.This work provides a strategy to solve the fluorescence quenching problem arising from the heavy-atom effect of Pt(II),and offers an alternative approach to tune the emission wavelengths of discrete SCCs in the same solvent.In chapter three,phenothiazine-based dipyridyl donor ligands LM1-LM3 and LP1-LP3 with different angles were successfully prepared,from which a series of organoplatinum metallacycles A1-A3,B1-B3 and C1-C3 with different sizes were successfully prepared through coordination-driven self-assembly.The photophysical properties of metallacycles A1-A3,B1-B3 and C1-C3 in the solution showed that their emission wavelength largely depended on the functional group para to the tertiary amine.The fluorescence color of metallacycles was tuned by switching the functional group para to the tertiary amine,which changed push–pull electronic properties of luminescent molecule.In addition,metallacycles B1-B3 displayed the higher emission intensity in solution(with the fluorescence quantum yield up to 61%).More importantly,the PET and ICT properties of metallacycles could be switched by by oxidation,which offered the self-assembled organoplatinum metallacycles with high fluorescence quantum yields and tunable fluorescence wavelengths.In addition,the ultra-long phosphorescence and white fluorescence of the metallacycles were observed through the dual stimulation of temperature and chemistry,which realized the tunable lifetime and emission wavelength.Multi-color luminescent films were successfully prepared.Different colors were observed at different temperatures and different delay times.These metallacycles were expected to be applied for multiple anti-counterfeiting,information encryption and storage,and optoelectronic devices.In chapter four,benzothiadiazole-based tetrapyridyl ligand A and B were successfully prepared,from which two fluorescent metallacages Cage A and Cage B were successfully prepared through coordination-driven self-assembly.Metallacages Cage A and Cage B can bind tetraphenylporphyrin(TPP),zinc tetraphenylporphyrin(Zn TPP)or platinum tetraphenylporphyrin(Pt TPP)at a ratio of 1:1in acetone or acetonitrile by solvophobic effect.Through the host-guest interaction,the emission wavelength of the supramolecular assembly can be tuned.Compared with the host Cage A,the guest TPP,the host Cage B and the complex TPP(?)Cage B,the host-guest complex TPP(?)Cage A exhibited higher singlet oxygen generation rate.For the catalytic oxidation of the thioether,the turn-over frequency(TOF)of TPP(?)Cage A was 6 times the sum of the TOF of the host Cage A and the guest TPP.In addition,the host-guest complex TPP(?)Cage A can catalyze the oxidation of aromatic sulfide or aliphatic sulfide into the corresponding sulfoxide quantitatively.This strategy of host-guest interaction synergistically improved the efficiency of catalytic conversion of singlet oxygen,which was expected to be applied to other catalytic systems.In chapter five,a truxene-faced Zn₄L₄ tetrahedron was obtained through the subcomponent self-assembly,which was capable of binding the smallest hydrocarbons in solution.By deliberately incorporating inward-facing ethyl groups on the truxene faces,the resulting partially-filled cage cavity was tailored to encapsulate methane,ethane,and ethene via van der Waals interactions at atmospheric pressure in acetonitrile,and also in the amorphous solid state.Interestingly,gas capture showed divergent selectivities in solution and the amorphous solid state.The selective binding may prove useful in designing new processes for the purification of methane and ethane as feedstocks for chemical synthesis.