Investigation On The Design And Synthesis Of RIV-type AIEgens And The Performance Of Copper-iodine Cluster-based MOFs Constructed By RIV-type AIEgens

Aggregation-induced emission(AIE)is a photophysical phenomenon that molecules in the aggregated state exhibit stronger emission than that in the single molecule state.This phenomenon overcomes the disadvantage of fluorescence quenching caused by the aggregation of traditional fluorescent molecules.Millions of AIE luminogens(AIEgens)have been designed and synthesized by researchers in the past twenty years,which are widely used in various fields such as biological imaging,fluorescent sensor and display lighting materials.Restriction of intramolecular motion(RIM)mechanism is one of the most important AIE mechanisms for designing AIEgens,which can be categorized into restriction of intramolecular rotation(RIR)mechanism and restriction of intramolecular vibration(RIV)mechanism.Thus far,most of the reported AIEgens are designed based on the RIR mechanism(RIR-type AIEgens),AIE systems based on the RIV mechanism(RIV-type AIEgens)are still extremely rare due to their complex structure,complicated synthetic procedures,difficult derivatization and associated high costs,which seriously restrict their practical application.Therefore,it is a challege to develop new RIV-type AIEgens with low cost and excellent fluorescence properties.In this work,we mainly focus on the development of new RIV-type AIEgens with macrocyclic structure and exploring their applications in the construction of multifunctional copper-iodide cluster-based metal-organic frameworks(MOFs).The main work is summarized as follows:1.A new kind of RIV-type AIEgens with macrocyclic structure of oxacalix[2]arene[2]pyrazine(OAP)are designed,which can be synthesized in a facile manner by a one-step catalyst-free reaction using commercially available materials.Meanwhile,the yields of the synthesis reactions are greater than 50%,indicating low cost of OAP AIEgens.The mechanism shows that OAP have butterfly-like structures,the pyrazine units resemble two vibrating wings.RIV mechanism is the source of their AIE properties because the intramolecular vibrations can be limited in aggregated state.Furthermore,OAP molecules have electron donor-acceptor(D-A)structures,which can undergo intramolecular charge transfer(ICT)process in their excited state,making them exhibit diverse luminescence properties in different environments.More importantly,the pyrazine groups in OAP exhibit potential coordination abilities with metal ions,making OAP be suitable for use as bridging ligands.Hence,OAP have broad application prospects in the field of coordination chemistry.2.On the basis of the above work,multifuctional OAP molecules are prepared by introducing specific functional groups.Different groups including triphenylamine,triphenylphosphine and fluorescein are introduced into the OAP skeleton.Firstly,by introducing triphenylamine groups,a blue-emitting molecule of oxacalix[2]arene[2]pyrazine(OPa P)is obtained.OPa P exhibits blue emission,which suggested that the fluorescence emission of OAP can be regulated from invisible to visible region.Secondly,oxcalix[2]triphenylphosphine[2]pyrazine(OPp P)is synthesized,which has two triphenylphosphine moieties.Compared with other OAP molecules,OPp P has more potential coordination sites.Thirdly,after the combination of fluorescein and OAP,oxacalix[2]fluorescein[2]pyrazine(OFP)is obtained.OFP exhibits obvious photo-induced emission change upon UV light irradiation.Under UV light irradiation,fluorescein can be rapidly released from the molecular skeleton of OFP,forming fluorescein sodium with strong green fluorescence.In this part,functional groups are introduced into the OAP skeleton,endowing OAP with tunable wavelength emission,multiple coordination sites,and photoresponse properties,expanding their application potential.3.OAP own pyrazine coordination groups,which are ideal ligands for the construction of MOFs.Using OAP as bridging ligands,a series of luminescent copperiodide cluster-based MOFs(1-10)are prepared.Multifunctional applications are realized by using these luminescent MOFs.Ultrafast luminescence switching induced by guest molecules is realized in the OAP-based MOF of 1.Mechanism study reveals that the intramolecular vibrations of OAP ligands can be restricted by the incorporated guest molecules in the pores of 1,leading to emission enhancement.The luminescence change in 1 by the adsorption/desorption of guest molecules is reversible,indicating good fatigue resistance.Owing to the intense yellow emission and high stability,the OAP-based MOF of 3 is successfully used for the construction of white light-emitting diode light(LED).Meanwhile,the growth rate of 3 is quite rapid,endowing it with potential applications for encrypted information storage.In addition,the OAP-based MOF of 4 exhibits an excellent mechanochromic phenomenon.Experiments show that alterations in cuphilic interactions are the key to discoloration.The work in this chapter provides theoretical basis and practical reference for the application of RIV-type AIEgens in copper-iodide cluster-based MOFs.This research enriches the limited kinds of RIV-type AIEgens,offers additional selections of bridging ligands for the construction of luminescence MOFs,and provides a visual model for understanding the effect of RIV process on the luminescence properties of MOFs.