Quinoline-based Fluorescent Chemosensors For Detecting Metal Ions

Metal ion fluorescent chemosensors can realize fast detection of specific metal ions, possessing advantages such as high selectivity, high sensitivity, and convenience. In environmental science and life science, it has become one of the most interesting research areas to design and synthesize high-selective and high-sensitive fluorescent chemosensors for metal ions.Recently, in biomedical research, two-photon microscope (TPM) has grown up into a widely used tool, since two-photon fluorescent sensors own lower phototoxicity and better spatial orientation comparing to single photon ones. Besides, it effectively increases the penetration ability of chemosensors, and reduces cell auto-fluorescence. In this thesis, a series of quionline based fluorescent sensors were designed and synthesized. The optical properties and recognition mechanism of the sensors had been studied.1. Based on intermolecular charge transfer (ICT) mechanism, a larger conjugated system was linked to the6position of the quinoline, methoxy was used as electron donation group, and thus ICT process was achieved. Meanwhile, this larger conjugated system enables molecule good two-photon optical properties.2. By introducing different receptors to the second position of modified quinoline, including Di-2-picolylamine (DPA), DPA derivatives and Schiff alkali group, selective recognition of Zn2+and Cd2+ion was realized respectively, and crystal structure of some coordination complex was obtained. Meanwhile, the optical properties of the sensor and their relationship with the structure have been studied. The results show that better coplanarity can lead to better optical properties.3. The FRET fluorescence theory is used to design fluorescence sensor RQ6, which contains both rhodamine and quinoline chromophore. The fluorescence spectrum manifests that the ligand can achieve good affinity to Fe3+ion. Biological imaging demonstrates that RQ6can use800nm two-photon laser as excitation source so as to make up the disadvantage of small Stock’s displacement in rhodamine system, which greatly increases the detection sensitivity. 4. Sensor’s reponse to pH and the cell toxicity have been tested to prove that the sensor has a good biological adaptation. pH sensitivity and cell toxicity of sensors was tested to prove they were quite proper to biological application. Simultaneously we studied the probes’bio-imaging capability and it turned out to be excellent, moreover, the three sensors can effectively distinguish different ions in cells, respectively.