Design And Synthesis Of Novel Organic Small Molecule Fluorescent Probes And Their Application In The Detection Of Phosgene

Phosgene(COCl₂)is a highly toxic gas,which is not easy to be noticed because it has no color and tastes very similar to newly mown hay.Phosgene was also used as a chemical weapon in World War I and World War II,causing a large number of deaths.At present,phosgene is widely used as a raw material for the industrial production of many pesticides,medicines,polymer materials and organic synthesis intermediates.In addition,unlike other chemical warfare agents,the production and sales of phosgene are not strictly controlled by law.Once it leaks during use or is used by terrorists to make chemical weapons for terrorist activities,it will seriously affect public health and safety.Therefore,under the more and more widespread application of phosgene and the disadvantages of traditional phosgene detection methods,combined with the superiority of organic small molecule fluorescent probes,a variety of fluorescent probes for detecting phosgene have been born.In this paper,we mainly carried out the following work:(1)Chapter 2:Based on the 7-nitro-2,1,3-benzoxoxadiazole(NBD)fluorophore,we designed and synthesized three turn-on organic small molecule phosgene fluorescent probes NBD-TACN,NBD-EDA and NBD-PZ.The probe NBD-TACN uses1,4,7-triazacyclononane as the recognition group,which can provide multiple N atoms and lone pairs of electrons,and phosgene combined the 4 and 7 position-NH groups in triazacyclononane structure to produces internal cyclization and blocks its PET effect on the NBD fluorophore.The reaction between NBD-TACN and phosgene produces a strong green fluorescence at 525 nm.NBD-EDA and NBD-PZ are based the common ethylenediamine and piperazine groups to recognition groups,which can also block the PET effect on the NBD fluorophore after being combined with phosgene,and produce extremely strong green fluorescence at 530 nm and 540 nm,respectively.In solution,the three probes all have the advantages of fast response(completed within 20 s),high selectivity and high sensitivity(the detection limits are1.2 n M,20.1 n M and 27.4 n M,respectively)for phosgene sensing.Of course,in terms of selectivity and sensitivity,NBD-TACN is superior to NBD-EDA and NBD-PZ.Therefore,we also successfully developed a portable test strip for real-time detection of phosgene in the gas phase based on the NBD-TACN.(2)Chapter 3:Based on the bis-benzimidazole fluorophore,we designed and synthesized a turn-on organic small molecule phosgene fluorescent probe BBMMN,which can quickly combine with phosgene to produce a six-membered cyclic carbamylation product BBMMN-Phos,produces extremely strong blue fluorescence emission at 428 nm and the relative quantum yield increases by 8.2 times.The response of BBMMN to phosgene is fast(completed within 30 s),high selectivity and high sensitivity(the detection limit in solution is as low as 3.3 n M).In addition,the portable test strip based on this probe can easily perform visual and fluorescent detection of gaseous phosgene.(3)Chapter 4:Based on the benzimidazole fluorophore,we first proposed a facile bifunctional organic small molecule fluorescent probe BMA for the detection of phosgene and nitrite.BMA had fast response(1 min),high selectivity and sensitivity(the limit of detection was 1.27 n M)to phosgene in CH₃CN solution(containing 10%DMSO),which manifested as a ratiometric fluorescent mode from 416 nm to 480 nm.The response of BMA to nitrite in HCl solution(p H=1,containing 10%CH₃CN)was also highly selective and sensitive(the limit of detection was 60.63 n M),which shown as a turn-off fluorescent mode at 485 nm.In addition,two portable chemosensors(BMA-loaded TLC plates and test strips)had also been successfully manufactured for the detection of phosgene in the gas phase and nitrite in solution,which displayed good responses.Most importantly,BMA had also been successfully used for detection of nitrite in food samples,and a good recovery(88.5%-107.2%)was obtained by adding standard sodium nitrite.(4)Chapter 5:Based on the imidazo[1,5-?]pyridine fluorophore,we designed and synthesized a turn-on organic small molecule fluorescent probe PMPY-NH₂,which can be transformed into a ketone structure through the ESIPT mechanism to rapidly,high selectively and sensitively(detection limit is 2.68 n M)combine with phosgene.The conjugation plane of the probe is increased due to the formylation reaction between the amino group and the benzimidazole ring,which is manifested by the generation of bright sky blue fluorescence at 455 nm and the absolute quantum yield increases by nearly 5 times.In addition,we have also developed a portable test strips based on PMPY-NH₂for the detection of gaseous phosgene in the environment.The test strip can respond to gaseous phosgene as low as 1 ppm,which has extremely high sensitivity.So,PMPY-NH₂can be widely used in actual testing in the future.