Synthesis And Characterization Of Thiophene-containing Diarylethenes As Fe³⁺ And Tryptophan Sensors

In recent years,heavy metals have had a great impact on chemical,physiological and environmental detection.Among heavy metals and transition metals,iron accounts for more than 5%of the crust and is the fourth largest element,playing an important role in many biochemical processes.Iron is an indispensable element for human beings.It is involved in metabolism,DNA synthesis and repair,etc.,which makes people interested in detection methods for quantitative analysis of iron ion.The most significant amino acid in the human body,tetrapophan,is integral to biological processes such as plant growth,animal development,and protein synthesis.Meanwhile,tryptophan is also one of the main factors that determine biodiversity and protein activity.Therefore,it is of great importance to monitor iron and tryptophan in a variety of environments through efficient,simple and cost-effective techniques.Diarylethene derivatives have the advantages of high thermal stability,fast response time,good fatigue resistance,reversible open and closed loop conversion,and good fluorescence conversion performance.Therefore,base on the Schiff base condensation reaction,three diarylethene fluorescent chemosensors were developed and synthesized,and their detection properties for Fe³⁺and tryptophan were studied.The results are as follows:（1）The synthesis and characterization of compounds（DY1o）modified by hydrazine thiocarformamide are described.The optical properties of DY1o were studied by absorption and fluorescence spectra in DMSO:H₂O=1:1.It is found that DY1o has good photoswitching performance,and it shows good specific recognition to Fe³⁺.When iron ion is present,the test solution changes from colorless to yellow and is fluorescently quenched,and the anti-interference performance is excellent.By titration test,DY1o and Fe³⁺were further determined to be complexed in a ratio of 1:1,and the detection limit was as low as 10.45×10^-7mol/L,and it has been applied to the actual water sample detection and paper test.（2）A compound（DY2o）modified by 2,2’-bithiophene was designed and synthesized.The optical properties of DY2o were studied by absorption and fluorescence spectra.It is found that DY2o has good photoswitching performance under the condition of pure water,and shows obvious selective response to fluorescence quenching of Fe³⁺,and excellent anti-interference performance,which is attributed to the coordination between DY2o and Fe³⁺.By titration test,the complexation ratio of DY2o to Fe³⁺was confirmed to be 1:1 and the detection limit was as low as 44.5×10^-8mol/L.The mechanism of DY2o to recognize Fe³⁺was studied by nuclear magnetic titration and ESI-MS,and was used in paper test.（3）Compound DY3o modified by hydrazylpyrimidine was designed and synthesized,and its optical properties were studied.In the DMSO environment,DY3o showed specific recognition of tryptophan,and the probe solution showed a change from no fluorescence to blue fluorescence in the presence of tryptophan.The complexation ratio of DY3o to tryptophan was 1:1 and the detection limit was as low as 17.4×10^-8mol/L.The mechanism of DY3o on tryptophan was simulated by nuclear magnetic titration and ESI-MS,and was tested on paper.