Synthesis Of Spiropyran-based Fluorescent Sensor For The Identification Of Multiple Metal Ions

In the past few years,spiropyrans have shown excellent performance in many fields including drug controlled release,chemical sensing,biological probes due to its discoloration from open loop to closed loop.Furthermore,the mechanism of the complexing reaction between ions and spiropyrans has also been applied to environmental monitoring for quicker,easier and more sensitive organic fluorescent probe reagents.This thesis centres on the chemical modification of indoline moiety and salicylaldehyde by introducing proline,methoxy,benzamido,etc to improve the binding capacity between the merocyanine and metal ions.The aim of this research is to develop novel spiropyran fluorescent probes with strong anti-interference,high sensitivity and single-ion-detection.This thesis has main three tasks as below.In the first part,hydroxyethyl modified spiropyran compound was synthesizedby the reaction between 3-（2-hydroxyethyl）-1,1,2-trimethyl-1H-benzo-[e]indol-3-ium bromide and 2-hydroxy-5-nitrobenzaldehyde.Based on this novel spiropyrans of SP1 was obtained by the dehydration reaction.The SP1 solution can quickly and effectively identify Fe³⁺,Cr³⁺and Al³⁺by naked eye recognition.The results of UV absorption and fluorescence emission spectra show that the ultraviolet absorbance and fluorescence intensity of metal ions have obvious changes.It hasμM level detection limit and good linear dependence.In addition,after dropping a variety of interfering metal ions,the results showed that SP1has strong anti-interference ability.Secondly,besides the indoline moiety modification,the structure of salicylaldehyde is another key factor.Two novel spiropyrans of SP2 and SP3 were prepared by combing 3-（2-carboxyethyl）-1,1,2-trimethyl-1H-benzo[e]indol-3-ium bromide with azo or methoxy group modified salicylaldehyde compounds at the yield of 72%and 78%,respectively.Compared with three-ions detection ability of SP1,better selectivities of SP2 and SP3 for two-ions detection were confirmed.Both SP2 and SP3have good metal ion anti-interference abilities and the detection limits were about 10^-6 mol·L^-1.In the third part,the key factor of interaction between solvents and specific groups were investigated.Based on the spiropyran with carboxyethyl group,a novel spiropyran SP4 was synthesized by the reaction with aniline at high yield of 85%.It can achieve single metal ion(Cu²⁺)detection and be recycled for 3 times.In general,the above four spiropyran compounds realize the recognition of different metal ions,and the synthesis conditions are mild and easy to control.Among them,SP1 has the strongest anti-interference ability.SP2 and SP3 modify salicylaldehyde structure to realize bimetallic ion recognition.Finally,SP4 containing amide structure is successfully synthesized by the guess of binding group,and the high selective recognition of single copper ion is realized.