The Design, Synthesis And Sensing Properties Of Fluorescent Probes Based On Terbium Complexes And The Derivatives Of Iminocoumarin

Supramolecular chemistry, as an interdisciplinary running through many fields such as physics, biology and chemistry, has promoted the development of materials science, information science and life science. The applications of molecular recognition in life science, food science, materials science, environmental science, public security intelligence and industrial and agricultural production have become an important area. Fluorescent probe plays a vital role in molecular recognition due to their high selectivity, sensitivity, and relatively simple handling. Therefore, the design and synthesis of efficient fluorescent probes is still in high demand.The dissertation focused on the recongnition of cations (H+, Cu2+and Hg2+), anions (phosphates), and small molecules (Hey, Cys and GSH) using rare earth complexes, iminocoumarin derivatives as fluorescent probes. The main works are as follows:1. Tb(Ⅲ) and Eu(Ⅲ) complexes have been synthesized as the potential pH probes using a tripodal 5-Br substituted-salicylic ligand (H3L1). The resulting L1·Tb complex exhibited high sensitivity in the physiological pH range with significant "off-on-off" fluorescence changes in aqueous solution. Furthermore, this unique rare-earth complex has been successfully used to monitor pH variations within HeLa cells. The pH response could be attributed to the decomposition process of L1·Tb.2. A Tb(Ⅲ) complex using a tripodal 4-CH3 substituted-salicylic ligand (H3L2) has been synthesized for the highly selective fluorescent recognition of phosphates in aqueous solution. It showed significant "on-off’fluorescence changes upon the addition of phosphates, which was attributed to the inhibition of the "antenna" effect between the ligand and Tb(Ⅲ) after incorporation of phosphates.In addition, Tb(Ⅲ) complex can be used for the construction of molecular logic gate as a combination of a NOT-NAND and AND by using the fluorescence changes.3. A bifunctional probe L3 based on the iminocoumarin scaffold for differential response of Cu2+ and Hg2+ in fluorescence mode and UV-vis absorption mode was demonstrated. In addition, probe L3 can be used for the construction of a molecular logic gate with NOR and INHIBIT logic functions by using the fluorescence changes. The response for Cu2+was attributed to the CHEQ (chelation-enhanced quenching) effect produced by the paramagnetic nature of Cu2. The fluorescence quenching for Hg2+was attributed to the spin orbit coupling effects from Hg2+.4. Two probes (L4-L5) for detection of biothiols with iminocoumarin scaffold containing 2,4-dinitrobenzene sulfonyl group are designed and synthesized. Further studies revealed that L5 can detect Hcy, Cys and GSH over other amino acids in PBS buffer solution, which was ascribed to the biothiol-promoted specific N-S cleavage of L5 and the hydrolysis of iminocoumarin. As a result, a coumarin derivative, which bears strong fluorescence character, is obtained.