Synthesis Of Salicylaldehyde Schiff Base Fluorescent Probes And Research On Its Recognition Of Aluminum Ions

In recent years,due to the discharge of industrial waste,the content of aluminum ions in nature has increased year by year,and the potential toxicity and harm of aluminum ions have also been valued by people.Therefore,the detection of aluminum ions has become a hot research topic.The salicylaldehyde Schiff bases have p-?-? conjugation system,at the same time the-C=N-and-OH structural units are easy to combine with metal ions to produce fluorescence effect.Therefore,it can be used as a fluorescent probe for thedetection of metal ion.In this paper,three kinds of "turn on" type bis-salicylaldehyde Schiff base fluorescent probes were designed and synthesized.The results show ed that these fluorescent probes could be used for rapid,efficient and specific detection of aluminum ions.The main research work of this paper is as follows:1.Starting from 4,4'-hydroquinone,5,5'-bissalicylaldehyde?2-2?was prepared by Duff reaction.After the condensation of 2-2 and 6-amino-m-cresol,the fluorescence probe?2-3? was obtained in 72.3% yield.The probe could realize the selective recognition of aluminum ions in methanol solution and avoid the interference of Ca²⁺,Hg²⁺ and other metal ions.When the concentration of aluminum ion was in the range of 25-55 ?m,the fluorescence intensity had a good linear correlation with the concentration,and the detection limit was 5.4×10-9 mol/L,which could realize the trace detection of aluminum ion.Mass spectrometry data analysis showed that the complex ratio of probe molecules to Al3+ was 2:1.The feeding experiment of mini parrot fish showed that the probe had certain biocompatibility and application prospects in the field of biological detection.2.Bissalicylaldehyde?3-2? was synthesized by formylation of 4,4'-dihydroxydiphenylmethane with hexamethylenetetramine in acid condition.The molecule 3-2 was condensed with 3-chloro-2-hydrazinylpyridine.The fluorescence probe?3-3?of bissalicylaldehyde Schiff base was obtained in 77.4% yield.In DMF solution,the probe could combine with Al3+ to produce strong fluorescence effect.The detection limit of the probe was 9.4×10-7 mol/L,which indicated that the probe had high sensitivity for the identification of aluminum ions andcould realize the trace detection of aluminum ions.Through the analysis of mass spectrometry data,the complex ratio of probe to Al3+ was speculated to be 2: 1.A rapid detection test paper was prepared with the fluorescent probe.The experimental results showed that the test paper had the characteristi cs of convenience,quickness,and strong operability,indicating that the probe had good application value.3.Bissalicylaldehyde?4-2? was synthesized by formylation of bisphenol A.the molecule 4-2 was condensed with 2-picolinylformazide,and the fluorescence probe?4-3? of bissalicylaldehyde Schiff base was obtained in 68.4% yield.The probe could recognize aluminum ions selectively in DMF solution,but Cu²⁺,Ni²⁺ and other metal ions have some interference on the probe's recognition of aluminum ions.The detection limit was 6.2×10-8 mol/L,which met the trace detection standard.The mass spectrometry data showed that the ratio of the probe to Al3+ was 2:1.At the same time,the fluorescent probe was made into a rapid detection paper for Al3+,and the experimental results showed that the paper had good Al3+ recognition effect.In this paper,all intermediates and products were characterized by NMR,IR and HRMS.