Synthesis And Properties Of Novel Coumarin Fluorescent Small- Molecules And Their Corresponding Rare Earth Complexes

Coumarins have attracted much attention of researchers due to their excellent physiological activities and fluorescence performance,and it played an important role in many fields.In this article,based on our previous works,two series novel ligands with chromophore coumarin and their corresponding rare earth complexes were designed and synthesized,respectively.Their structures were confirmed by various analytical methods.And the luminescence and protein coupling properties of them were also investigated.The target compounds L were synthesized through Knoevenagel reaction by using N,N-diethylaminosalicy-laldehyde,hydrazine hydrate and para-substituted benzaldehyde as raw materials,and their corresponding europium complexes[Eu（NO₃）₃L^1-4]·2H₂O were also synthesized.The relationship between luminescence properties and concentration,solvent of the target compounds were investigated.The results found that they can emitting green fluorescence.At a concentration of 40μmol·L^-1,their luminescence intensity were the strongest,and position of their emission wavelength were affected by the polarity of solvent.Their luminescence intensity were also affected by the substituent group in ligands,the introduction of electron-absorbing groups can enhance their fluorescence intensity.According to the electron absorption ability of substituent groups.The effect of various substituent group in ligands on the fluorescence intensity and fluorescence quantum yield is ordered:nitro（-NO₂）>chlorine（-Cl）>methoxy（-OCH₃）>hydroxy（-OH）.Among them,The fluorescence intensity of 7-（diethylamino）-N’-（4-nitrobenz-ylidene）-2-oxo-2H-chromene-3-carbohydrazide（L³）was the strongest and its fluorescence quantum yield was also the highest.The properties analysis results showed that complexes[Eu（NO₃）₃L₃]·2H₂O possessed good thermal stability and well luminescence performance.They can emit the characteristic red light of europium ions,and have a well application prospect in the field of photoluminescent materials.Their luminescence intensity was affected by the substituent groups,and the effect was the same as that of the target compounds.Among them,the fluorescence intensity of complex[Eu（NO₃）₃L³]·2H₂O was the strongest,and its fluorescence quantum yield was also the highest.The target compounds P were synthesized through Knoevenagel reaction by4-hydroxysalicylaldehyde,diethyl malonate and substituted aniline,and their corresponding terbium complexes[Tb（NO₃）₃P^1-4]·2H₂O were also synthesized.The relationship between fluorescence properties and concentration of the target compounds were investigated.The results show that they can emit blue fluorescence in ethanol solution.At a concentration of 40μmol·L^-1,their luminescence intensity were the strongest.Their luminescence intensity were also affected by the substituent group in ligands,the introduction of electron-absorbing groups can enhance their fluorescence intensity.The effect of various substituent group in ligands on the fluorescence intensity and fluorescence quantum yield is ordered:methyl formate（-COOCH₃）>hydrogen（-H）>chlorine（-Cl）>methoxy（-OCH₃）.Among them,the fluorescence intensity of ethyl 7-（2-（（4-（methoxycarbonyl）phenyl）amino）-2-oxoeth-oxy）-2-o-xo-2H-chromene-3-carboxylate（P⁴）was the strongest,and its fluorescence quantum yield was also the highest.The target compounds ethyl 2-oxo-7-（2-oxo-2-（phenylamino）etho-xy）-2H-c-hromene-3-carboxylate（P¹）was selected for BSA binding.The UV analysis showed it was coupled with BSA successfully,and the coupling ratio was 17.After the coupling,the PBS solution of P¹-BSA can emit strong green fluorescence.The results indicated that ligand P can be used as fluorescent labeling,and have a well application prospect in fluorescent biomarkers.The properties analysis results showed that complexes[Tb（NO₃）₃P^1-4]·2H₂O possessed good thermal stability and well luminescence performance.They can emit the characteristic green light of terbium ions,and have a well application prospect in the field of photoluminescent materials.Their fluorescence intensity was affected by the substituent groups,and the effect was the same as that of the target compounds.Among them,the fluorescence intensity of complex[Tb（NO₃）₃P⁴]·2H₂O was the strongest,and its fluorescence quantum yield was also the highest.