Synthesis And Ion Recongnition Of Fluorescence Probes Based On 2,5-diphenyl-1,3,4-oxadiazole Derivatives

Molecular recognition as an important branched research area in supramolecular chemistry, plays crucial roles in environmental and biological sciences. During recent years, 2,5-diphenyl-1,3,4-oxadiazole derivatized have attracted more and more attention because of they display excited state intramolecular proton transfer(ESIPT) property. They are widely used in fluorescent probe because of their good fluorescence properties. In thesis, some relay recognition chemosensors and reactive recognition probes were designed and synthesized, and ion recognition behaviors are studied according to2,5-diayrl-1,3,4-oxadiazole. The details are as follows:1. A new two dipicolyl amine(DPA) dangled 2,5-diphenyl-1,3,4-oxadiazole derivatized sensor L1 has been designed and synthesized. Sensor L1 displays excited state intramolecular proton transfer(ESIPT) property in buffered water solution(HEPES 10 mM, pH = 7.4) L1 behaves highly selective and ratiometric fluorescence responses to Zn2+ L1 through 1:2 binding ratio. The in situ generated L1-2Zn2+ complex can serve as a relay recognition sensor toward PPi and S2- via further complexation and Zn2+ sequestering processes respectively. Thus,multi-analyte and relay recognition of L1 through modulating ESIPT have been achieved.2. 2,5-diphenyl-1,3,4-oxadiazole derivative-based fluorescent sensor L2 and L3 were designed and synthesized. In HEPES buffered(10 mM,pH =7.4) water solution, L2 exhibits high selectivity towards Zn2+ with a red-shifted emission. L2 binds Zn2+ through a 1:2 binding stoishiometry. The in situ formed L2-2Zn2+complex can act as a relay recognition probe to pyrophosphate(PPi), PPi can further bind the zinc ion in the complex and results in emission blue shift. Through successive interaction of L2 with Zn2+ and PPi, the excited state intermolecular proton transfer(ESIPT) property was perturbed, thus a ratiometric emission outputrelay recognition was achieved. A new 2,5-diphenyl-1,3,4-oxadiazole-based L3 was synthesized and applied as a highly selective and sensitive fluorescent probe for relay recognition Cu2+ and S2- in water(Tris 10 mM, pH = 7.0) solution. L3 exhibits an excellent selectivity to Cu2+ over other examined metal ions with a prominent fluorescence “turn-off” at 392 nm. L3 and Cu2+ form a 1:2 binding ratio complex with detection limit of 3.38 μM. The on-site formed L3-2Cu2+ complex exhibits excellent selectivity to S2- with fluorescence “off-on” response via Cu2+displacement approach.3. A new 2,5-diaryl-1,3,4-oxadiazole derived ratiometric fluorescent probe OXDNP for hydrogen sulfide recognition has been developed. Probe OXDNP displays highly selective and sensitive detection to HS- over other anions and thiol-containing amino acids in DMSO solution with fast response and large Stokes shift characteristics. Through HS- induced thiolysis of the dinitrophenyl ether, the excited state intramolecular proton transfer(ESIPT) featured precursor was released, which led to dual fluorescence emission “turn on” and ratiometric emission behavior of the sensing system. Probe L4 displays highly selective and sensitive detection to GSH over other amino acids in DMSO solution. Through GSH induced hydrolysis acrylate, the excited state intramolecular proton transfer(ESIPT) featured precursor was released, which led to dual fluorescence emission red shift and ratiometric emission behavior of the sensing system.