Study On Design, Synthesis And Properties Of Colorimetric Anion Probes In Aqueous Media

Fluorescent and colorimetric chemosensors are widely used in selective detection of metal ions and anions.There are lots of advantages for fluorescence chemosensors such as high selectivity,sensitivity and simplicity.Colorimetric probes are especially attractive,as they allow 'naked-eye' detection of the analyte without resorting to any expensive instruments.In this thesis,a series of novel simple colorimetric anion probes,whose anion sites were hydrogen donor such as thiourea,urea,carbazole,amide and phenol,were designed and synthesized and their spectral properties and recognition mechanism were investigated.In addition,the probes P1,P8 and P9 are capable of detecting or recognizing anions of interest in aqueous solution by the naked-eye method.The results are summarized as follows:1.The probes(P1-4) based on urea or thiourea derivatives were designcd and synthesized.In aqueous solution(DMSO:H₂O(95:5,v/v)),P1 could bind anions with a visible color change from light purple to deep purple.P1 could qualitatively detect fluoride in toothpaste in virtue of UV-vis spectrum.In DMSO,P2,whose chromophore and anion binding sites were-NO₂ and a urea moiety,respectively,could also act as a colorimetric anion probe.Two different anion binding sites:a urea unit and a carbazole uinit were exploited by the probes P3 and P4.The anion binding ability of P3 was much stronger than that of P4,owing to that there was an electron withdrawing part(-NO₂) in P3.2.The colorimetric anion probes P8 and P9 based on hydrazone derivatives were designed and synthesized.In competitive medium such as DMSO:H₂O (95:5,v/v),the color of solution of P8 changed from yellow to red,which allowed to naked-eye detection,upon addition of basic anions.The results of the competition experiment indicated that the other anions tested hardly interfered the detection of AcO^-ion.P9 exhibited a fluorescent enhancement response to anion due to complexation rigidifying the probe, simultaneously accompanied with significant color changes. 3.The probe P12 with an azo unit as a chromophore and a thiourea moiety as anion binding sites was designed and synthesized.There were two isomers: an azo form and a hydrazone form for P12 and an azo form dominated in DMSO solution.Upon interaction with basic anions,the azo form of P12 would be promoted to the hydrazone form,simultaneously accompanied with great changes in UV-vis spectrum,fluorescence spectrum and color.4.The fluorescent probes P13 and P14 based on intramolecular charge transfer (ICT) and photo-induced electron transfer(PET),respectively,were designed and synthesized.In DMSO solution,P14 exhibited a dual-wavelength change response to anions based on ICT and acted as a ratiometric fluorescent anion probe.The PET probe P14 exhibited fluorescence quenching response towards to anions.Upon gradual addition of anions,the anion binding sites of P14 deprotoned stepwise along with 'naked-eye' color changes.In addition,the urea derivatives P5-7,the macrocyclic compound P15 etc. were synthesized.But they could not be used as colorimetric anion probes.