Structure Modification And Performance Study Of Salicylaldehyde Schiff Base Type Fluorescence Probe

Metal ions are the key research contents in the field of environmental chemistry,life and medical science.The detection of metal ions in aqueous solution is a hot research topic in analytical chemistry.In recent years,metal ion fluorescent probes have drawn much attention because of their good selectivity,high sensitivity and rapid response.Salicylaldehyde Schiff bases have a C=N-,-OH structural unit,so they have prominent coordination ability with the metal,in addition,because such molecules have a larger conjugate system or D-?-A structural characteristics,they show excellent fluorescence properties,but due to the poor solubility of their metal complexes in the aqueous phase and the organic phase,application in the field of fluorescence detection is limited.The main work of this paper is to modify the structure of salicylaldehyde molecules,namely,introduce oleophilic groups to the salicylaldehyde molecules to increase the solubility of the metal complexes in organic solvents,meanwhile investigate the fluorescence properties of the metal complexes and the possibility as metal ion fluorescent probes.The main research work of this paper is as follows:Three kinds of salicylaldehyde derivatives,namely 5-methyl-3-?,?-di-methyl-?-phenyl salicylaldehyde?3a?,3,5-di-?,?-di-methyl-?-phenyl salicylaldehyde?3b?and 5-t-octyl-3-?,?-di-methyl-?-phenyl-salicylaldehyde?3c?were synthesized using alkylphenol as starting material via F-K alkylation and formylation reaction.The three kinds of salicylaldehyde derivatives were condensed with o-aminophenol to generate three new Schiff base fluorescent probes?4a,4b,4c?with planar conjugated structures.The three kinds of fluorescent probes were complexed with Zn²⁺,Cu²⁺,Mn²⁺,Ni²⁺ and Co²⁺,respectively.We conducted structural characterization and fluorescence property study of these synthetic ligands and complexes.Results showed that the three kinds of fluorescent probes had good recognition properties for Zn²⁺,of which the fluorescence intensity of 4b and Zn²⁺ complex was about 5 times as the ligand,4a and 4c were 2 times and 2.5 times,respectively.Compared with Zn²⁺,the fluorescence intensities of complexes synthesized by Cu²⁺,Mn²⁺,Ni²⁺,Co²⁺ and the three ligands were lower than those of the ligands.Nine novel L-amino acid salicylaldehyde Schiff bases?7a-i?with D-?-A structure were prepared by condensation reaction of 3a-c and three natural amino acids,respectively.The nine new Schiff bases were used to complex with Zn²⁺,Cu2 +,Mn²⁺,Ni²⁺ and Co2 + respectively.We conducted structural characterization and fluorescence property study of these synthetic ligands and complexes.Results showed that complexes of the nine ligands and Zn²⁺ had strong fluorescence emission,the fluorescence intensity of the complexes were more than 1.5 times than those of the ligands,of which 7f was about 10 times.Compared with Zn2 +,the fluorescence intensities of complexes synthesized by Cu²⁺,Mn²⁺,Ni²⁺,Co²⁺ and the nine ligands were lower than those of the ligands,which indicated that those nine ligands had excellent selectivity as Zn²⁺ fluorescent probe.We studied the effect of four metal ions,namely,Cu2 +,Mn2 +,Ni2 +,Co2 + on the detection of Zn²⁺when the ligand 7f was used as fluorescent probe.Results showed that Cu²⁺ exhibited a strong quenching effect on the fluorescence emission of complexes generated by 7f and Zn²⁺,while other ions and their mixtures had little effect.We studied the crystal structure of the complex generated by 7b and Cu2 +.The single crystals' X-ray diffraction of the complex showed that the crystals were orthorhombic and P21 space group.In this paper,three kinds of salicylaldehyde derivatives,12 salicylaldehyde Schiff base ligands and 60 kinds of metal complexes were synthesized,all of which were new compounds and have not been reported in the literature.