Synthesis And Performance Study Of Fluorescent Probes Based On Binol-diform

Metal ions are not only essential elements of the ecological environment and the human body,but also very valuable strategic resource.The qualitative and quantitative detection of metal ions is of great significance.In recent years,using fluorescent probes to detect metal ions has become a research hotspot,because of high sensitivity,good selectivity,rapid response and easy operation.However,most of the existing fluorescent probes are planar conjugate structures,and few molecules with spatial stereoscopic cross structures have been studied.Meanwhile,orthohydroxyimine has a good coordination ability with metal ions due to its C=N-and-OH structuralunits.Therefore,1,1’-binaphthalene with stereospecific structure was selected as the precursor in this paper.Schiff base compounds were designed and synthesized as fluorescent probes by introducing the structural unit of ohydroxyimine.The main work of this paper is to synthesize three kinds of Schiff bases after the synthesis of 2,2’-dihydroxy-1,1’-linked-3,3’-di-naphthaldehyde using 2-naphthol as starting material,meanwhile design comparative experiment in which 2-hydroxy-1-naphthylaldehyde was used to synthesize Schiff base compound to investigate the fluorescence intensity of a Schiff base metal complex with a stereospecific structure and the possibility of being as metals ion fluorescent probes.The main research work of this paper is as follows:Starting from 2-naphthol,Binol-diform was synthesized through coupling,protecting group,formylation and hydrolysis,respectively.After condensation with o-aminophenol and 2-amino-5-nitrophenol,two new Schiff base fluorescent probes 7a and 7b were synthesized.The two kinds of fluorescent probes were complexed with Zn2+,Cu2+,Ni2+,Pr3+,La3+ and Ce3+,respectively.The structure and fluorescence properties of the synthesized ligands and complexes were studied.Results showed that the prepared two kinds of fluorescent probes showed good recognition performance for Ce3+,of which the fluorescence intensity of 7a and Ce3+ complex was 5 times as the ligand,while 7b and Ce3+ complexwas about 3.5 times,the rest of the ions showed no significant change compared to the ligand.However,in the comparative experiment,fluorescence intensity of the complexes formed by 4a and 4b with metal ions showed no significant change,of which 4a and 4b were formed by the condensation of 2-hydroxy-1-naphthaldehyde with o-aminophenol and2-amino-5-nitrophenol,respectively.Binol-diform and 2-hydroxy-1-naphthaldehyde were condensed with three kinds of amino acids respectively to generate 6 amino acid Schiffbases 9a-c and 11a-c,then these Schiff bases reacted with Zn2+,Cu2+,Ni2+,Pr3+,La3+ and Ce3+ to form the corresponding metal complexes.Structural characterization and fluorescence property study of these synthetic fluorescent probes and complexes were adopted.Results showed that the complex of 9a-c ligand and Ce3+ had strong fluorescence intensity,which was 4 times as the ligand.However,the fluorescence intensity of the complex formed by the metal complexes with 11a-c did not change significantly.The interference experiments of Zn2+,Cu2+,Ni2+,Pr3+ and La3+ on the detection of cerium ions using 7a and 9b ligands as fluorescent probes were studied.Results showed that only Cu2+ weakened the fluorescence intensity of 9b and Ce3+ complexes slightly,while other ions had little effect.