Synthesis And Properties Of Novel Schiff Base Derivatives Of Salicylaldehydes And Coumarin And Their Europium Complexes

Rare earth elements have excellent photoelectromagnetic physical properties,can form a stable structure with other organic ligands,a wide variety of new materials with excellent performance,the performance of ligands and corresponding rare earth complexes and related application research have good development prospects.In addition,various Schiff base derivatives have strong coordination ability with metal ions and simple synthesis steps.Their rare earth organic complexes are widely used in chemical catalysts,biomedicine,chemical coatings,anti-counterfeiting materials,fluorescent labels and other related fields.In this paper,five novel salicylaldehyde pyridine Schiff base compounds and three coumarin Schiff base compound fluorescent ligands were designed and synthesized,and the physical and chemical properties of the target complex were explored.Its main work is as follows:（1）Using 2-hydroxybenzaldehyde and 5-methoxy-2-aminopyridine as the initial raw materials,the target ligand L^1-5is prepared through the Schiff base reaction between the aldehyde group and the amino group.Then the ligand is coordinated with europium ion,and the related structure of the complex is accurately proved by the use of characterization methods such as molar conductivity,infrared spectroscopy and thermogravimetric analysis,and the electrical properties of the complex are explored by cyclic voltammetry and reference method.The chemical properties and fluorescence quantum yields were obtained by calculating the HOMO and LUMO energy levels of the complexes to obtain the effects of different substituents in the ligands on the europium complexes,and the strength of the complexes to emit fluorescence was explored.（2）Using resorcinol and ethyl 3-oxobutanoate as the initial raw materials to obtain the intermediate product 4-methylumbelliferone,after a classic duff reaction,7-hydroxy-4-methyl-8-aldehyde is obtained Coumarin,and 2-aminopyridine with each para substituent to obtain 7-hydroxy-4-methyl-8-（（pyridine-2-pyrimidine）methyl）coumarin derivative L^6-8.Then ligands were coordinated with europium ions,and the related structures of the complexes were accurately proved through the use of characterization methods such as molar conductivity,infrared spectroscopy and thermogravimetric analysis.The three complexes all emit red fluorescence of europium ions,and the complexes contain the electron-donating group OCH₃with the best fluorescence performance,the NO₂^-containing complexes are relatively poor,and the substituents on the complex fluorescence and HOMO and LUMO energy levels are also Exploring,the effect is OCH₃>H>NO₂.Containing OCH₃has the best fluorescence performance.The effect of different ions on the fluorescence intensity of the complex is explored.The results show that the complex has a specific recognition function for F^-,and the response sensitivity of the complex is 1.0×10^-5to 2.2×10^-5.The europium complexes synthesized in this subject have good fluorescence properties and good thermal stability,and have good application prospects in the field of luminescent materials and biological detection.