Synthesis Of Bis-Schiff Bases And Their Recognition Property For Metal Ions

Fluorescent probes can quickly and accurately detected trace metal ions and selectively recognized many kinds of metal ions.Moreover,they have the advantages of rapid detection,high sensitivity.In recent years,the important issue of fluorescence detection of metal ions in the chemical,biological and environmental science occupied an unshakable position.In this paper,more than forty kinds of bis-Schiff base compounds were designed and synthesized,and the bis-Schiff base compounds were synthesized and their ion recognition property was studied one by one.Six kinds of bis-Schiff base fluorescent probes with good recognition performance were screened by spectral titration,UV titration,mass spectrometry,Job's,nuclear magnetic titration and other methods to explore the coordination ratio of the probe molecules to metal ions and their coordination modes,and further speculate their selective recognition mechanisms.The actual application of these fluorescent probes to real water samples was also investgated in this paper.The main content is illustrated as follows:1.Using 1,6-di(3'-hydroxy-4'-formylphenoxy)hexane,1,4-di(3'-hydroxy-4'-formylphenoxy)butane and 5,5'-methylene salicylaldehyde reacted with a series of aliphatic amines,hydrazides and some heterocyclic amine to generate a series of bis-Schiff base compounds.The synthesized products were characterized by the methods of 1H NMR,FT-IR etc..2.Three bis-Schiff base-type fluorescent probes with good selective recognition abilities to Zn2+ were found in the experiments: 1,4-di(3'-hydroxy-4'-formylphenoxy)butane based Schiff base(probe 1),1,6-di(3'-hydroxy-4'-formylphenoxy)hexane based Schiff base(probe 2),and 1,4-di(3'-hydroxy-4'-formylphenoxy)butane based Schiff base(probe 3).With the addition of Zn2+,the fluorescence intensity of these systems were greatly enhanced.Probes 1 and 2 in DMF/H2O(9/1,v/v)solution,probe 3 in DMF/H2O(19/1,v/v)solution,have obvious recognition effects for Zn2+.Job's Law,Molar ratio method,UV-vis spectrum titration,1H NMR titration and LC-MS spectrometry showed that probes 1,2 and 3 formed complexes of 1:1 ratio with Zn2+,and both probes 1 and 2 were reversible fluorescent probes.In addition,application studies show that probe 3 can be applied to the determination of Zn2+ in a certain concentration range of the real water samples.We further speculated the recognition mechanisms of these three probes to Zn2+ in detail.3.Three bis-Schiff base-type fluorescent probes with good selective recognition abilities to Al3+ also were found in the experiments:1,4-di(3'-hydroxy-4'-formylphenoxy)butane based Schiff base(probe 4,5 and 6).The results of fluorescence spectra titration,Job's,molar ratio,1H NMR titration and LC-MS spectrometry showed that the probes 4,5,6 and Al3+ formed the complexes with the ratio of 1:1,probes 4,5 and 6 are reversible fluorescent probes.We also hypothesized the recognition mechanisms of these three probes to Al3+.