Synthesis And Ion Recognition Properties Of Platinum Complexes Based On Salicylaldehyde Derivative

Anions and cations are widely present in the environment and human body and are closely related to human health.Among anions,fluorine is one of the trace elements in the human body.A moderate intake of fluorine helps protect dental health and prevent osteoporosis,but a large intake may lead to dental fluorosis,fluorosis,nerve damage and kidney stones and other diseases.Zinc ions play an important role in maintaining normal metabolism and physiological functions,but too much or too little zinc ions in the body may have an impact on human health.For example,zinc deficiency may lead to developmental delays and neurological disorders,while too much zinc may interfere with immune function,slow down the wound healing process and hinder growth and development.Therefore,it is necessary to test for fluoride and zinc ions.Although there are many techniques and instruments available for fluoride ion and zinc ion detection,colorimetric and fluorescent chemical sensors have received much attention because of their simplicity of operation,low cost,high sensitivity,rapid response,and naked-eye recognition.In this dissertation,chemical sensors that can be used for the selective recognition of fluoride ions and zinc ions were synthesized based on Pt（Ⅱ）complexes using salicylaldehyde and its derivatives as recognition units.The main work is summarized as follows:1.Chapter 1 briefly outlines the status of research on luminescent probes,fluorine and zinc ion probes,the status of research on ion probes based on Pt（Ⅱ）complexes,and salicylaldehyde in chemical sensing,on the basis of which the design ideas of this thesis are presented.2.The higher Lewis acidity of the-OH unit enables the detection of fluoride ions by hydrogen bonding with F^-and deprotonation.In Chapter 2,two Pt（Ⅱ）complexes with aggregation-induced emission（AIE）properties functionalized with salicylaldehyde derivative ligands,Pt-ppy and Pt-2Fppy,were synthesized,and the structures of the complexes were characterized by NMR,mass spectrometry and single crystal.Their AIE properties were confirmed based on the studies of luminescence behaviors in THF-H₂O mixed solution and poly（methyl methacrylate）（PMMA）doped films,and the AIE mechanisms of the restrained intramolecular rotation and restrained molecular configuration deformation was studied by theoretical calculation.The selectivity of the probes for anions was investigated by UV-Vis absorption spectroscopy and fluorescence emission spectroscopy.The results showed that only fluoride ions could make the probe solutions immediately show obvious orange-yellow luminescence"on",and the detection limits of the probes for F^-were as low as 10^-7 M,and the chemical reaction ratio of the probes with F^-were 1:2.¹H NMR titration experiment and theoretical calculations show that the interactions between the probes and fluorine ions are achieved by deprotonation of-OH unit.3.F^-can destroy the intramolecular hydrogen bond of salicylaldehyde Schiff base and block its excited-state intramolecular proton transfer（ESIPT）process.In addition,the salicylaldehyde Schiff base has an N and O environment suitable for metal cation coordination,and an ESIPT process can occur between OH units and adjacent imines bond C=N bonds.If the ESIPT process within the probe molecule is blocked or coordinated with metal ions,the photophysical property of the chemical sensor based on salicylaldehyde Schiff base will change.Therefore,Pt-ppy-ABP was prepared on the basis of Pt-ppy in Chapter 3,and the structure of the complex was determined by NMR,mass spectrometry and single crystal.Pt-ppy-ABP can be used for the detection of fluorine and zinc ions.In the selective recognitions of anions,fluoride ions make the DMSO probe solutions change from weak yellow luminescence to bright red luminescence and correspondingly from colorless to pink under natural light.In the selective recognitions of cations,which are carried out in mixed solvent,zinc ions interact with probe leading to the luminescence of the probe’s DMSO-H₂O solutions changes to bright green,and the probe after interaction with zinc ions can be recovered by dihydrogen phosphate,enabling the repeated using of the probe.The detection limits of both fluoride and zinc ions were as low as 10^-7 M.The ¹H NMR titrations and theoretical calculations showed that the mechanism of interaction between the probe and the fluorine ion was that the ESIPT process was blocked by the deprotonation of the-OH unit caused by F^-and the coordination of Zn²⁺with the-OH unit,resulting in the change of the luminescence color and the solution color after the interaction between the probe and the ion to achieve the corresponding detection.