Studies On Fluorescent Sensors Based On Coumarins And Lanthanide Complexes

Molecular-based sensor is used widely in the fields of analytical science, bioscience and materials science, and it has become a very active research area currently. Especially fluorescent molecular sensor has attracted increasing attention because of its advantages including rapid response, high sensitivity, and excellent selectivity. So a large number of fluorescent sensors for detection of bioactive molecules/cations/anions and sensing of temperature and pressure.In this paper, fluorescent sensors including LBZC、LACH、LAZB·Tb、LAOC for detection of hydrogen peroxide, cysteine, hydrogen sulfide and sensing pressure had been developed. Moreover, several terbium complexes with salicylic acid derivatives as ligands were designed and synthesized; at the same time, a turn-on terbium-based luminescent probe for Hg2+was developed.The dissertation is divided into six parts:(1) Both design principle and recognition mechanism of rescent sensors ere introduced. Moreover, the developments of sensors based on coumarins and lanthanide complexes were reviewed emphatically.(2) To develop piezochromic materials, six coumarin-based fluorescent dyes were synthesized. Among them, LAOC was a piezochromic material, and showed 20nm red-shift after grinding. The relationship between molecular and structue property was described. Furthermore, the change of the molecular structure around grinding was inferred from relative experiments.(3) A coumarin-based two-photon hydrogen peroxide (H2O2) fluorescent probe LBZC was designed and synthesized by utilizing the unique chemical reactivity of benzil and hydrogen peroxide, together with the d-PeT mechanism to control the fluorescence. It exhibited high selectivity and high sensitivity toward H2O2, and was successfully applied to cell imaging of intracellular H2O2 levels with two-photon microscopy. Besides, a density functional theory (DFT) calculation was performed to demonstrate that the benzil was a fluorescence quencher.(4) A new coumarin-based two-photon cysteine (Cys) fluorescent probe LACH was designed and synthesized by utilizing the Micheal-addition reation, together with the ICT and ESIPT mechanism to control the fluorescence. It exhibited high selectivity toward Cys over glutathione (GSH) and homocysteine (Hey), especially over GSH, and it was successfully applied to tissue imaging of intracellular Cys levels with two-photon microscopy. Moreover, the probe was able to monitor the conjugate addition product LACH-Cys in fluorescent emission behavior, which was barely observed in previously reported Cys probes.(5) A terbium complex-based turn-on luminescent hydrogen sulfide (H2S) probe LAZB·Tb based on the reduction reaction of azide with H2S to amine was present. It showed high selectivity for H2S over competitive anions and small-molecule biothiols. Moreover, the long luminescence lifetime of the probe facilitated the implementation of time-delayed experiment, whereby the fluorescence with short lifetime from sample could be readily gated out.(6) To extend lanthanide complex with better luminescence property, seven salicylic acid-based ligands were synthesized. Through the course of the study, 5-acetyl substituted salicylic acid (5-ASA) was found to be a good antenna for Tb3+, and the quantum yield of relative terbium complex (1·Tb·5-ASA) could reach 21.03%. On the basis of this positive result, a turn-on luminescent Hg2+ probe 1·Tb·5-ESA was synthesized by utilizing the Kucherov reaction.