Synthesis And Ion Recognition Research Of Receptors Based On Benzimidazole(Benzothiazole) And Oxadiazole

As 2-(2′-aminophenyl)benzimidazole, 2-(2′-aminophenyl)benzothiazole and 2,5-diphenyl-1,3,4-oxadiazole are important kinds of nitrogen containing heterocyclic compounds, they have been widely used in the fields of biological sciences and medical sciences. With the development of research, people find that these kinds of compounds have good fluorescence properties. These fluorophores behave fluorescence characteristic in organic solvent even in water environment. Therefore, in recent years, more and more attention has been devoted to these compounds with the application in metal ion recognition. We designed and synthesized a series of fluorescent sensors based on the ESIPT mechanism of 2-(2′-aminophenyl)benzimidazole, 2,5-diphenyl-1,3,4-oxadiazole, and 2-(2′-aminophenyl)benzothiazole derivative in this thesis and got some meaningful results. The details are as follows:1.Briefly introduced the concept of supramolecular and the development trend in recent years and new sensing mechanisms, simultaneouly, summarized the appli cations of compounds of benzimidazole, benzothiazole, oxadiazole in the ions recognition and progesses.2.A new 2-(2′-aminophenyl)benzimidazole derivatized fluorescent sensor(L) that behaves relay recognition of Cu2+ and S2- in water solution(p H 7.4) has been developed. Sensor L displays excited-state intramolecular proton transfer(ESIPT) featured two emission bands and performs highly selective and sensitive recognition to Cu2+ through two emissions simultaneous quenching. The on-site formed L-Cu2+ complex exhibits excellent selectivity to S2- with fluorescence ‘‘off–on’’ response via Cu2+ displacement approach, which exerts ESIPT recovery. Thus, through modulation the ESIPT state of sensor L, relay recognition of Cu2+ and S2- in water has been achieved.3. A novel fluorescent sensor OXD and OXTC derived from 2,5-diphenyl-1,3,4-oxadiazole derivative was designedand synthesized. In HEPES buffered(10 m M, p H 7.4) water solution, sensor OXD displays highly selective,sensitive and rapid response to Zn2+ with ratiometric fluorescence changes. Sensor OXD coordinates with Zn2+ ion through amide form with a 1:1 binding stoichiometry. The observed Zn2+ induced red-shifted andenhanced fluorescence emission of OXD is attributed to Zn2+binding promoted ESIPT process emission. Potential applications of OXD to detect Zn2+ ions in real water samples and living cell imaging were also demonstrated.Then the sensor OXTC can recognize the Zn2+ in Tris-HCl 10 m M, p H = 7.4 aqueous solution and distinguish the Cd2+ from Zn2+. Sensor OXTC displays highly selective and sensitive recognition to Zn2+ through the relevant spectral measurement and calcalation, in addition,the detection limit was 9.06×10-7M.4. A highly selective and sensitive fluorescent Zn2+ sensor N-(2-(benzo[d]thiazol-2-yl)phenyl)-2-((pyridin-2-ylmethyl)amino)acetamide that derived from 2-(2′-aminophenyl)benzothiazole has been developed. In aqueous solution(HEPES/CH3CN=4/6, v/v, HEPES 20 m M, p H=7.4), sensor APBTP displays highly selective recognition to Zn2+ over other metal ions with a distinct longer-wavelength emission enhancement. Sensor APBTP binds Zn2+ through its amide form with a 1:1 binding stoichiometry, which switched on the excited-state intramolecular proton transfer(ESIPT).5.A new rhodamine–benzothiazole conjugated colorimetric sensor RHBT that exhibits sequential recognition to Cu2+ and S2- in CH3CN/HEPES buffer(v/v = 1:1, HEPES 10 m M, p H = 7.0) solution has been developed. Sensor RHBT displays highly selective and sensitive recognition to Cu2+ with a ratiometric behavior, and the resultant RHBT-Cu2+ complex can act as a highly selective S2- sensor via Cu2+ displacement approach.The Cu2+ and S2- recognition processes are rapid and reversible, and the Cu2+ and S2- inputs can result in an INHIBIT logic gate.