Synthesis,Structure And Room Temperature Phosphorescence Study Of Azacyclic Carboxylic Acid Molecules And Related Coordination Polymers

Room temperature phosphorescence(RTP)has a wide range of applications in bioimaging,chemical sensing and security encryption.Most of the traditional phosphorescent materials are natural inorganic compounds.Such inorganic materials are not easy to synthesize and have poor structural tunability.The study found that azacyclic carboxylic acids have structural features such as aromatic groups and heteroatoms(N,O),which can promote the intersystem crossing(ISC)process,thereby increasing the probability of generating triplet excitons.The formation of coordination polymers(CPs)by linking these organic phosphors with metal ions through coordination bonds can effectively suppress the nonradiative decay of chromophores,and then enhance their RTP properties.In addition,the highly tunable structural features of the complex polymers facilitate the exploration of the relationship between crystal structures and RTP properties,opening the way for the development of organic molecular-based materials with persistent room temperature phosphorescence(p-RTP)properties.The first chapter summarized the research status of RTP,and put forward the research content of this paper for the crystal structures and luminescence principle of CPs.The second chapter was based on 5-(1H-imidazol-1-yl)nicotinic acid(Himpc)to obtain the co-crystal Himpc·HNO3(1)and two metal-organic hybrids[Cd(impc)2(H2O)2]n(2)and[Zn(impc)2(H2O)4]·2H2O(3).The RTP lifetime of 3 was as long as 405 ms and exhibited a rare time-resolved color change afterglow effect.The crystal structure analyses showed that H-aggregation can stabilize triplet excitons and promote RTP emission by enhancing π…π coupling.The third chapter revolved around the synthesis of 5-(1H-benzo[d]imidazol-1-yl)nicotinic acid(Hbinc)to obtain a singlecomponent molecular crystal of Hbinc(4)and three complex polymers {[Cd(binc)2]n(5),[ZnCl(binc)]n(6)and[Co(binc)2]n(7)}.The experimental data showed that the RTP lifetimes of 4～6 gradually became shorter,but they were all longer than those of pure Hbinc powder.It was found that inhibiting the non-radiative transition of Hbinc molecule through crystallization can effectively enhance RTP,and the D-A structure with a suitable twisted conformation can reduce ΔEST and promote the ISC process.The fourth chapter revolved around the synthesis of 1-(4-carboxyphenyl)-1H-1,2,4triazole-3-carboxylic acid(H2tbc)to obtain a pure organic molecular crystal(8)and two complexes[Cd(tbc)(H2O)2]n(9)and[Sr(Htbc)2(H2O)3]n(10).The photophysical properties test results showed that 10 exhibited multiple emission peaks and had a maximum RTP lifetime of 552 ms at 500 nm(264 ms at 548 nm;211 ms at 585 nm).It can be obtained by analysis that the RTP performance of organic ligands may change with different metal ions.Therefore,we can modulate the luminescence properties of organic phosphors by selecting suitable coordinating ions.Chapter 5 designed and synthesized two nitrogen heterocyclic carboxylic acids,namely lithium 5-((1Hbenzo[d][1,2,3]triazol-1-yl)methoxy)isophthalate(Li2btmp)and lithium 5-((2(pyridin-2-yl)-1H-benzo[d]imidazol-1-yl)methyl)isophthalate(Li2pbmp),respectively.We used these two newly synthesized ligands to synthesize two novel complexes[M2(btmp)2(H2O)3]n[M=Zn(11),Mn(12)]and[M(pbmp)]n[M=Cd(13),Mn(14)],respectively,and the crystal structures of these four complexes were studied in detail,in order to develop more efficient and more valuable RTP materials provided the premise.In this paper,based on azocarboxylic acids and related complexes,the factors affecting their room temperature phosphoresis properties were studied in detail from the perspective of crystal structures,and interesting time-resolved color changing long afterglow materials were developed,which has important practical significance.