Design,synthesis And Fluorescence Sensing Properties Of Carboxylic Acid Ligand Transition Metal Complexes

With the problem of water pollution has been increasingly serious in recent years,it is an emergency to find an efficient and sensitive method to detect pollutants in water.At present,the main methods for detecting pollutants in water include high performance liquid chromatography,inductively coupled plasma,electrochemical method,fluorescence method and so on.Due to its rich and varied structure and adjustable pore size,coordination polymer materials have been widely applied in many fields,especially in fluorescence sensing.A series of coordination polymer materials are designed and synthesized in this paper as fluorescence sensors with low detection limits to detect organic matter,metal ions and pesticides in water.Specific research contents are as follows:1.In this paper,the use of transition metal ion Zn/Cd/Cu and carboxylic acid ligand:2,2’,3,4’,5-diphenyl ether pentacarboxylic acid（H₅depa）or 5-methoxyresorcinic acid（H₂zgt）,and select different nitrogen-containing ligand,through high temperature hydrothermal design synthesis of eight new complex materials:[Zn₂（Hdepa）（dye）₂]_n（CP1）,{[Cu₂（Hdepa）（2,2’-bipy）₂（H₂O）₂].2H₂O}_n（CP 2）,[Cd₂（depa）（H₂O）.C₅H₅N⁺]_n（CP 3）,[Cu（H₂depa）（1,3-bis）]_n（CP 4）,{[Cd（zgt）（2,2’-bipy）（H₂O）].H₂O}_n（CP 5）,[Zn（zgt）（1,10-phen）]_n（CP 6）,{[Zn（zgt）（2,2’-bipy）（H₂O）].H₂O}_n（CP 7）,{[Cd（zgt）（1,3-bis）（H₂O）].H₂O}_n（CP 8）.Among them,nitrogenligands including:2,2’-pyridine（2,2’-bipy）,4,4’-pyridine（4,4’-bipy）,1,10-Phenanthroline（1,10-phen）,1,3-double（4-pyridyl）propane（1,3-bis）,2,2’-2 pyridine amine（dye）.CPs 1-8 were characterized by X-ray single crystal diffraction,infrared,thermogravimetric,XRD,etc.,which provides the design and synthesis ideas for transition metal complexes based on pentacarboxylic acid and dicarboxylic acid ligands.2.Among the four complexes synthesized based on H₅depa,the two complexes CP1 and CP 2 with the best fluorescence properties were selected for fluorescence sensing experiments.CP 1 is sensitive to benzaldehyde（BZH）,tetracycline（TC）,2,4,6-trinitrophenol（TNP）,fluridine（Flu）,Fe³⁺,Cr₂O₇^2-,CP 2 can selectively detect p-nitrophenol（4-NP）and Fe³⁺,and finally explore the fluorescence sensing mechanism through fluorescence lifetime,XRD and UV-visible absorption test.So CP 1 and CP 2can be used as potential multifunctional sensors to detect contaminants in water.3.The d¹⁰ structure based on Zn and Cd is combined with the ligand to produce strong emissions.Four Zn and Cd complexes CPs 5-8 designed and synthesized by using H₂zgt showed that the solid fluorescence emission of CPs 5-8 were superior to that of the ligand H₂zgt and the nitrogen-containing ligand.Therefore,the fluorescence sensing experiment of pesticide and nitro explosive was tested.CP 5 and CP 7 respond to p-nitrobenzoic acid（PNBA）in explosives,but CP 6 and CP 8 respond to 2,4,6-trinitrobenzoic acid（TNP）in explosives.All CPs 5-8 were sensitive to the pesticide fluridine（Flu）.and the mechanism of fluorescence sensing was discussed.Finally,CP 5,which is the most sensitive to Flu detection,was selected for real sample detection.