Room Temperature Phosphorescent And Environment Responsive Phosphorescent Materials Based On Aryl Ether Compounds

Due to the lifetime of triplet exciton and three spin multiple states,organic phosphorescence has broad prospects in sensors,biomedicine and organic optoelectronic materials.In order to obtain effective pure organic room temperature phosphorescence,we should not only improve the inter system transition efficiency,but also suppress the non-radiative transition and bimolecular quenching.With many years of research in the field of organic phosphorescence,we have known the basic photophysical process,which is conducive to the design of molecular systems.However,the application of sensitivity to phosphorescence remains to be developed.Until now,very few environment-responsive RTP materials are known,partially their intrinsic mechanism is unknown,and most of them are based on quenching mechanism,which has great limitations for molecular design and practical application.At the Ph.D.level,I devoted myself to the research of pure organic room temperature phosphorescence and its related applications,developed room temperature phosphorescence molecular system,and researched its functionality,from theory to practice,and explored the properties of organic molecules.The details are as follows.1.The construction of room temperature phosphorescence system of(electron donor)-sulfur-(electron acceptor).The phosphorescence emission can be obtained from the internal molecular design.Firstly,we reduce the energy gap between singlet and triplet by the charge transfer states in the electron donor and electron acceptor group,promoting intersystem crossing.Then we select sulfur atoms with heavy atomic effect to provide lone pairs to enhance the spin-orbit coupling cooperation.Finally,we choose sp3 connection to reduce the quenching of phosphorescence by intermolecular interaction.The absolute quantum yield of DSA molecule solid is up to 20%,and the molecule can effectively emit room temperature phosphorescence.By adjusting the donor and acceptor groups and theoretical calculations based on single crystal data,we conclude that the charge transfer state of the electron donor and electron acceptor is beneficial to triplet excitons.At the same time,the structure of sp3 forms a tetrahedral-like structure in the space to stabilize the luminescent molecules and reduce the ?-? quenching effect.Further fine-tuning the position of the electron acceptor group found that its luminescent properties have changed,which provides us with ideas and directions for the subsequent design of more excellent molecules.2.The construction of proton-activated "Off-On" room-temperature phosphorescent materials.Room-temperature phosphorescence(RTP)-based sensors have distinctive advantages over the fluorescence counterparts,such as larger Stokes shifts and longer lifetimes.Unfortunately,almost all RTP sensors are operated on quenching-based mechanisms given the sensitive nature of the emissive triplet state.Here we report a type of thioether RTP molecules that shows RTP "turn-on" when volatile acid vapors such as HCl are in contact.We integrate good proton acceptors such as pyridine and quinoline into our thioether system,and use the proton-activated charge transfer state in the molecule to generate green room-temperature phosphorescence.The detection limit of acid vapor is 8.3 mg/m3 and the quantum yield reaches 10%.To elucidate the underlying mechanism,model thioethers containing different donor/acceptor combinations are investigated via fluorescence spectroscopy and theoretical calculations aided by molecular coordinates obtained from single-crystal X-ray diffraction.It is revealed that a charge-transfer character in the phosphorescence state is crucial.The "turn-on"design concept may significantly broaden the sensing application scope for organic RTP molecules.3.Research on dual emission phosphorescence based on sp3 connection.Compared with fluorescent materials,room temperature phosphorescent materials have lifetime changes in the time dimension under environmental stimuli,which can be used as additional visual parameters.Therefore,the number of visual parameters can be increased from 2 to 3,which will greatly promote its practical application.Here,we show that by utilizing triphenylamine(TPA)as an electronic donor that connects to an acceptor via an sp3 linker,six TPA-based AIE-active RTP luminophores were obtained.Distinct dual phosphorescence bands emitting from largely localized donor and acceptor triplet emitting states could be recorded at lowered temperatures;at room temperature,only a merged RTP band is present.Theoretical investigations reveal that the two temperature-dependent phosphorescence bands both originate from local/global minima from the lowest triplet excited state(T1).In this way,we have introduced two time dimensions,and can further expand the visual parameters,which may provide important clues on the design and control of high-freedom molecular systems with complex excited-state dynamics.4.Design of environmentally responsive room temperature phosphorescent material with host-guest interaction.Most naphthalene ring molecules or larger conjugated molecules cannot emit RTP in the condensed state,and RTP can only be observed when dispersed in a rigid matrix,which greatly limits our applications.In this project,we use molecules with similar molecular structure to these macrocyclic compounds as the host,which can effectively disperse phosphorescent molecules in them,and obtain an amorphous RTP material with a phosphorescent quantum yield of more than 30%.We change the host and guest molecules to study the luminescence principle,and find that there is a strong electron coupling between the host and guest molecules,resulting in energy transfer.Using the influence of the host molecule on the guest,we designed the host molecule to contain a quenching group to obtain ammonia-activated RTP,which opened up an environmentally responsive room temperature phosphorescence system and application.