Studies On The Luminescent Chemosensors Based On Small Organic Molecules And Rare-earth Complexes

Metal ions and anions play an important role in environment and organisms. Many ions are closely related with human living and health and play a key role. However, over-use of some ions will damage the environment and living beings. Therefore, how to rapidly sense and detect metal ions and anions in both environment and organisms, furthermore, improve the detection sensitivity is a challenging but important problem, which has important theoretical and practical significance. In numerous studies, fluorescent chemosensors deserves special attention because it is highly selective, highly sensitive, convenient and rapid. A lot of new novel fluorescent chemosensors have been designed and successfully applied to detecte and recognize guest small molecules, including metal ions, anions and biological molecules. Recently, it is a hot topic of coordination chemistry to design and synthesize high selectivity and high sensitivity fluorescent chemosensors through coordination between sensors and metal ions. For further investigation of the recognization of organic small molecules fluorescent chemosensors to guest metal ions via coordination and the development of rare-earth complexes fluorescent chemosensors, we designed and synthesized three organic small molecules and one dual mode (fluorescent and colorimetric) fluorescent chemosensors based on our previous work. We studied their recognition to metal ions including Zn2+, Al3+and Cu2+through coordination, and furthermore achieved recognization of S2-by replacement reaction. Recognition mechanisms have been studied intensively. Otherwise, a novel amide type ligand was designed. Cage-like homodinuclear Eu, Gd, Tb and heterodinuclear EuTb complexes were obtainted by self-assembly of ligand and rear-earth ions. The study demonstrated that energy transfer processed from Tb (III) to Eu (III) in heterodinuclear rare-earth complex. Specific caged structure of complexes and energy transfer makes them potentially useful in the recognization of guest small molecules by fluorescent. Research results achieved supplies new methods for design organic small molecules and rare-earth complexes fluorescent chemosensors for design and apply of fluorescent chemosensors have theoretical significance and certain applied value.The thesis is divided into five parts:Chapter Ⅰ:A simple brief review about progress of organic small molecules and rare-earth complexes fluorescent chemosensors. Chapter Ⅱ:Designed and synthesized a detecting Zn2+chemosensor L1based on di-2-picolyIamine as metal ions receptor. Recognition mechanism studied demonstrated it was based on chelation enhanced fluorescence (CHEF) and prevents photoinduced electron transfer (PET) mechanism to achieve Zn2+induced fluorescence enhencement. Competition experiment suggested that Cd2+disturbed it recognized Zn2+. By improving on structure of chemosensor, designed and synthesized the other chemosensor L2based on acylhydrazone as Zn2+receptor. The chemosensor can recognize Zn2+and the detection process are not affected by Cd2+. Recognition mechanisms are CHEF effect and PET mechanism.Chapter Ⅲ:So far, most of metal ions fluorescent sensors are detect transition metal ions. Main group metal ions sensors are relative less. A good chemosensor L3detect Al3+based on acylhydrazone as receptor was designed and synthesized. The sensor has high selectivity for Al3+based on CHEF mechanism.Chapter Ⅳ:Cu2+has a pronounced quenching effect on fluorophores by mechanisms inherent to the paramagnetic species. We have designed and synthesized a chemosensor L4for Cu2+based on acylhydrazone as receptor. Emission intensity decreased upon addition of Cu2+. There is CuS precipitate formed upon addition S2-due to solubility product of CuS is very small (3.6×10-36). The fluorescent intensity retrieved when S2-was added into media through replacement reaction. A "on-off-on" type polyion fluorescent chemosensor was gained. The color change of the system from colorless to yellow and then to colorless was accompanied during the whole course, which would be detected easily by the naked eye. It was a polyion recognition dual mode (fluorescent and colorimetric) chemosensor.Chapter Ⅴ:To investigate the possibility of rare-earth complexes having specific structures applied to detect guest molecule. A novel amide type briged ligand was desgnized and syntheszied. L5and rare-earth ions self-assembled into a series of [2+2] caged structures of homodinuclear rare-earth complexes [Ln2(μ/2-L5)2(NO3)6(EtOH)2][Ln=Eu、Tb、Gd] and heterodinuclear rare-earth complex [EuTb(μ2-L5)2(NO3)6(EtOH)2]. Photophysical properties demonstrated that energy transfer from Tb (Ⅲ) to Eu (Ⅲ) in heterodinuclear rare-earth complex. It is hope applied to recognize small molecule ratiometric chemosensor based on complexes specific caged structures and energy transfer property.