Sensing Properties Of Salicylaldehyde Schiff Base And Its Derivatives

Salicylaldehyde Schiff base is an organic compound formed by the condensation of salicylaldehyde and its derivatives with primary amines.Due to its simple synthesis method,it is easy to form crystals and has excellent fluorescence performance with aggregation-induced enhancement?AIE?,which is interested by researchers.From the molecular structure point of view,the C=N double bond in the salicylaldehyde Schiff base molecule is in the ortho position with the phenolic hydroxyl group on the benzene ring,and can coordinate with most of the metal ions to form a metal complex with special function.It widely used in optical materials,catalysis,drug design,chemical sensors and biological probes,especially as fluorescent chemical sensors.On the one hand,the salicylaldehyde Schiff base itself exhibits no significant fluorescence or very weak fluorescence due to the fluorescence decay caused by the cis-trans isomerization of the excited state C=N in its molecule.Only after coordination with certain metal ions,isomerization is effectively prevented,thereby promoting fluorescence enhancement.This particular property provides an excellent platform for the development of metal cation fluorescence sensors.For example,through molecular design,salicylaldehyde Schiff base ligands can effectively realize effective identification of metal ions such as[Zn²⁺],[Cu²⁺],[Al³⁺],and[Pt²⁺].On the other hand,salicylaldehyde arylamine compounds belong to sensitive color-changing functional materials.Such materials are caused by superposition of two orbitals within the sub-molecules to cause rapid proton transfer within the molecules,which is an important basis for achieving charge transfer,transfer,and molecular switching.It has photochromic,thermochromic,piezochromic and non-linear optical properties and may be used in information storage,optical switching,and information display.Salicylaldehyde Schiff bases have received much attention due to their photoinduced and thermochromic properties based on proton transfer in excited molecules.Its unique photo-induced and thermally induced isomerization properties make it an ideal information storage material.Based on the above research fields,it can be seen that there is still a need for further research on the systemic photophysical sensing performance analysis of salicylaldehyde Schiff bases and derivatives.By introducing different substituents on the phenyl ring of salicylaldehyde?tert-butyl,halogen,etc.?and then condensing with aniline derivatives,a series of salicylaldehyde-based Schiff base compounds are produced.In this paper,the fluorescence detection probes for trinitrophenol?TNP?and sarin simulant diethyl chlorophosphate?DCP?are systematically summarized at home and abroad from the design,synthesis,characterization and performance testing of probes.Systematic research.The main research results are as follows:1.A small molecule DMA was designed as a fluorescent probe for the detection of aqueous TNP:simple benzene rings as the basic skeleton,diformyl as the acceptor group,and dimethoxybenzene donor units.The fluorescent material has typical intramolecular charge transfer characteristics,and has good AIE luminescence properties,exhibits good luminescence performance in a mixed solvent of THF/H2O,and easily self-assembles into a microcrystalline structure in the liquid phase,increasing.The luminescence intensity of DMA in solution is conducive to the improvement of the sensing performance.Aldehyde functional group can be hydrogenated with TNP-OH,so as to achieve the purpose of detection of aqueous TNP;at the same time,DMA has a suitable energy level,matching the energy level of TNP can ensure the occurrence of PET mechanism between the two compounds,further reduce the fluorescence intensity of the material.The stable hydrogen bonding and the synergy of the PET mechanism make the DMA fluorescent probe highly sensitive and highly selective for the detection of aquous TNP with a detection limit as low as 1.2×10^-7M.2.DBPFA and DBPFA-I based on salicylaldehyde Schiff base were designed for liquid phase detection of DCP.We strive to design and synthesize highly fluorescent salicylaldehyde Schiff bases in solution via structural modifications and find that they can be used for DCP detection.In our work,we reported a highly fluorescent DBPFA-I solution with a nucleophilic phenol anion structure.It can react with DCP with a detection limit of 1.94 nM,which is a very promising fluorescence sensor for rapid and simple DCP detection.However,the effect of HCl on the probe cannot be effectively avoided at present.This thesis systematically studied the application of salicylaldehyde Schiff base compounds in chemical sensing,and synthesized a series of organic light-emitting materials with excellent luminescent properties through modification of functional groups.On the other hand,in order to strengthen the application of these compounds,we applied it to the detection of TNP and DCP,and achieved good results.