Design,Synthesis And Fluorescence Properties Of Small Molecule Fluorescence Probe Based On 1,3,5-Triazine

The tridentate terpyridine-like compounds,such as 2,6-bis(pyrazolyl)pyridines,have been reported as ion probes for their extensive coordination abilities to the various metal ions and the special photophysical properties of their metal complexes.However,the difficulty and complication in synthesis and structural modification seriously restricted their application and development.In the past decade,a novel terpyridine-like platform,2,4-bis(pyrazol-1-yl)-1,3,5-triazine,has drawn much attention due to its convenient synthesis method.The 1,3,5-triazine is a fascinating?-electron-deficient aromatic molecule,and possesses the largest nucleophilic susceptibility among various nitrogen-containing heteroaromatic six-membered ring compounds.Meanwhile,1,3,5-triazine derivatives exhibit distinctive optical and electrical properties such as high fluorescence quantum yield,two-photon absorption and good electrochemical properties.Recently,some chemosensors based on 1,3,5-triazine have been developed for the detection of various analysts.In this thesis,we designed and synthesized a series of novel 1,3,5-triazine derivatives.All the compounds,as the classical donor-acceptor(D-A)type intramolecular charge transfer(ICT)systems,exhibited fantastic photophysical properties,such as large stoke shift and high quantum yield.Their properties of ion detection have been investigated in solution and living cell imaging.The concrete research content is as follows:Compounds 1-5 are synthesized by using 1,3,5-trichlorotriazine as starting materials,pyrazole,3,5-dimethyl parazole and benzotriazole as reactant.All compounds are characterized by 1H NMR,13C NMR and ESI-MS.The structures of 3 and 5 have been determined by X-ray crystallography.The photo-physical properties of 1-5 are studied in various solvents of different polarity.Due to solvato-kinetic effects,the fluorescence quantum yields of 1-5 are found decreased when the polarity of the solvent increases.It is notable that the fluorescence quantum yields of 3-5 are markedly lower than 1 and 2.Since the benzotriazole is a good electron acceptor,the introduction of benzotriazole causes the reducing of energy gap.According to the energy gap law,the non-radiative decay rate is increased due to the relatively low energy of the singlet excited state in these compounds.The specific binding of compounds 1-5 with different metal are investigated by UV-vis and fluorescence spectra.Compound 1 and 2 exhibit no specific selectivity towards metal ions;4 and 5 can be used as the potential fluorescent probe against Fe3+and Ag+.3 is utilized to the specific sensing of Fe3+ ions in a luminescence turn-off mode without the interference from other metal ions.Job plot analysis and ESI-MS reveal a 1:1 binding stoichiometry between 3 and Fe3+ with high binding constant(1.65 × 103 M-1)and low detection limit(6.3 ?M).The fluorescence "ON-OFF-ON"circle can be repeated by the alternative addition of Fe3+ and EDTA.By confocal microscopy,3 is cell permeable and suitable for monitoring intracellular Fe3+ in living cells.Hydroxyl and diethylamino-substituted 1,3,5-triazine derivatives 6-9 are synthesized successfully and characterized by 1H NMR,13C NMR and ESI-MS.The structure of 9 have been determined by X-ray crystallography.The photophysical properties of 8 and 9 at different pH conditions are studied.8 shows no pH response and not suitable as pH fluorescent probe.For 9,the fluorescence intensity at the maximum emission wavelength is continuously increased as pH increases,which demonstrates its potential application in pH monitoring.