Synthesis,Luminescence Behavior And Applications Of Nitrogen Heterocyclic Materials

Luminescent materials are widely used in fluorescent probes,biological imaging,photoelectric devices,intelligent response and so on.However,the traditional luminescent materials have a severe aggregation induced quench(ACQ)phenomenon at high concentration or aggregation state,which hinders the applications in solid states.This dissertation was devoted to the synthesis of different nitrogen heterocyclic luminescent materials.By regulating the molecular structure,especially the charge state of nitrogen heterocycles,the aggregation induced luminescence(AIE)behaviors were changed,These nitrogen heterocyclic luminescent materials were used in mechanical response,temperature sensing,organic light-emitting displays(OLEDs),recognition and detection of trace inorganic ions and etc.The excited-state intramolecular proton transfer(ESIPT)behavior and application based on nitrogen heterocyclic materials have also been studied in this paper.The main contents of this thesis are as follows:(1)The traditional AIE/AIEE materials only have weak Van der Waals force among molecules,and the stacking mode of the grinding powders is metastable,which can spontaneously return to a more stable polycrystalline state in short time.This uncontrollability is not conducive to their application in intelligent security.In this part,we synthesized four new imidazolium heterocyclic modified TPE organic salt compounds 3a,3b,4a and 4b.All of them have AIE properties,the crystal of compound 3a exhibited unique mechanical response property,and it is also sensitive to temperature.With the increase of temperature(24-78~oC),there are many phase transitions in the structure.This thermal response may be caused by the synergistic effect of nonradiative transition and structural transformation due to the molecular thermal motion.In addition,the compound 3a also has good water solubility and low toxicity.It can also be used for cell imaging,and the dyed cells still have large signal-to-noise ratio without washing process.Moreover,we used the four imidazolium salts as ligands to form Ag carbene complexes 5a,5b,6a and 6b.Among them,the complexes 6a and 6b exhibited high fluorescence quantum yields in dilute acetonitrile solution and solid state.(2)In order to overcome single channel fluorescence change of thermal responsive fluorescent materials,we successfully synthesized two new D-A type heterocyclic luminescent molecules PTZ-DRZ and ID-DRZ,which contain triazine core.Their structures and opto-electronic properties were investigated.The results show that PTZ-DRZ has multiple luminescence properties such as AIE,TADF and RTP.As a temperature response material,it is found that PTZ-DRZ can achieve multi-channel temperature response.This response mechanism was investigated via the molecular energy level.Moreover,PTZ-DRZ can also be used as luminescent material in OLEDs.(3)The existing fluorescent probes have many disadvantages for Pd detection,such as low selectivity,weak anti-interference ability and long response time.In order to detect the low concentrations of Pd effectively,we designed and synthesized a new ratio fluorescence sensors HPNI-1 for Pd detection,in which HPNI with AIEE property as fluorophore(imidazole heterocycles of HPNI can serve as H proton receptor,and thus achieve ESIPT processes under light excitation).Chloromethylpropyl ester as a recognition group was modified on hydroxyl groups of HPNI.HPNI-1 has high sensitivity to detect the Pd(detection limit is 1.34 n M)and ultra-high anti-interference ability(Pd:other metal ions=1:1000).The response time is fast(stable time=2 min).Moreover,we designed a specific imidazolium heterocyclic polymer ionic liquid(CP-AMIN),which can highly adsorb low concentration Pd(II)in aqueous solution.The maximum adsorption capacity is284.45 mg/g,and the maximum adsorption efficiency is 98.95%.The acidic thiourea solution can desorb Pd(II)from CP-AMIN.Having excellent recoverability,CP-AMIN have a broad application prospects in green separation.(4)Fluoride ions are of great importance to human health and environmental safety.It is urgent to achieve sensitive quantitative detection of fluoride ion.We designed and synthesized two new fluorescence sensors for F~-detection,HPNI-F and HPNIC-F.We selected HPNI and HPNIC as chromophores,and modified them with three isopropyl chlorosilanes on hydroxyl groups of the chromophores,thus blocking the ESIPT process on the imidazole heterocycles.After treatment with fluoride ion,the ESIPT process is resumed under UV excitation,resulting in the tautomerism of fluorophores and accompanied ratio fluorescence response.At the same time,the two probes have large Stokes shift,which provides new ideas for the design of fluorine ion probes in the future.