Design And Phosphorescence Properties Of Push-pull Small Molecules Based On Imidazole And Benzoic Acid

Organic phosphorescent materials with persistent room temperature phosphorescent(RTP)properties have attracted much attention due to their potential applications in emergency lighting,anti-counterfeiting and sensors.In recent years,more breakthroughs have been made in the field of room temperature phosphorescent materials.Here,based on the theory of crystal engineering and coordination chemistry,ultra-long room temperature phosphorescent materials with high efficiency and stability were designed and their intrinsic luminescence mechanism was explored to provide important theoretical support for structural design and optimization.By coupling carbazole with m-phthalic acid through the SUZUKI reaction,the organic molecule Cz IP was obtained.The supramolecular assembly of Cz IP with different metal ions was carried out via the coordination-induced crystallization strategy.Five coordination polymers(1-5)with excellent room temperature phosphorescence properties were synthesized.Through crystal engineering,the stacking pattern of Cz IP molecules can be effectively regulated,not only by monomer,dimer,but also by excimer and other arrangements.These compounds showed not only high fluorescence emission properties,but also emission characteristics of excimers were effectively regulated.Importantly,there compounds exhibit ultra-long-life room temperature phosphorescence(RTP).Compound 1 showed a long-life afterglow of 0.93 s at 545 nm at room temperature.In addition,compound 2 showed white light properties with CIE coordinates close to(0.33,0.33)through both fluorescence and phosphorescence emission.To our knowledge,This is the first luminescent coordination polymer with single-phase white light emission and time-dependent afterglow.It is worth mentioning that compounds 1-3 all have time-dependent afterglow properties.The synthesis of these materials has great potential for anti-counterfeiting applications.The experimental results show that the stacking mode of molecules plays an important role in the optical properties of materials,and the C-H···π interaction,intermolecular and intramolecular charge transfer interactions are beneficial to the emission of ultra-long RTP.Using imidazole as donor and benzoic acid as acceptor,we have designed a series of push-pull organic small molecules based on C-N coupling.Through the donor-Acceptor(D-A)system inside the molecule,it is beneficial to strengthen the Charge Transfer(CT),effectively reduce the energy gap difference between singlet and triplet states,promoting the intermolecular Intersystem crossing(ISC),and obtain the long-life room temperature phosphorescence.Through the study on the properties of small molecule luminescence materials,we found that the organic molecule show the dual emission characteristic of fluorescence and phosphorescence,and have a longer decay life,then,we will be the supramolecular self-assembly,won four crystal materials with good luminous performance were synthesized crystalline materials(6-9),and its performance have been simply analyzed.Therefore,we can make use of the differences in fluorescence and phosphorescence properties,as well as the properties of ultra-long-life room temperature phosphorescence emission,which further demonstrates its broad application in anti-counterfeiting,information encryption and other aspects,and also provides us with a important approach for the preparation of ultra-long pure organic room temperature phosphorescence molecules.