The Research Of Fluorescence Chemosensor And The Molecular Switch Based On The Benzo-Crown Ethers

The selective binding and the construction of molecular devices based on the crown ethers have become an interesting topic of supramolecular chemistry. Herein, we have designed and synthesized novel fluorescent chemosensor based on the benzo-crown ethers for metal ions, and obtained a series of supramolecular assembly based on the dibenzo[24]-crown-8 derivatives which can function as molecular switch. Their photophysical properties and assembly behaviors were further studied. The details are as follows:1. The history of supramolecular chemistry is briefly introduced. Then it emphasizes on the mechanism of fluorescent chemosensor and recent progresses in crown ethers. It also summarizes the new achievements of molecular machines.2. A novel fluorescent chemosensor modified with biarylpyridine unit for Mg²⁺ has been synthesized, and shows interesting fluorescent ON-OFF-ON processes through mediating its twisted intramolecular charge transfer state; A novel host composed of biarylpyridine and cyclodextrin moieties has been synthesized, which can form supramolecular inclusion complexes with acridine red dyes. And the reversible FRET property of the complex triggered by acid-base modulated intramolecular charge transfer process was investigated.3. A novel host molecule bearing a dibenzo[24]-crown-8 moiety and a dipicolinic acid group was synthesized, and its Tb³⁺ complex displayed a satisfactory luminescent emission. The tris[2]pseudorotaxane formed from the Tb³⁺ complex and ferrocene derivative reveals excellent reversible luminescent lanthanide behavior. Meanwhile, this supramolecular system can be used as the probe of Ca²⁺.4. Novel class of [2]catenane and pretzelane based on the dibenzo[24]-crown-8 modified with porphyrin were achieved, and the photophysical properties of the obtained [2]catenanes and pretzelane were investigatied.5. Several molecular double plug-socket species can be performed through modulating the disassembly and reassembly between bis(crown ether) host and secondary dialkylammonium guests. They can not only be regarded as switchable "molecular shields" to protect anthracene group from photooxidation, but also perform the functions of molecular keypad locks; A molecular elevator, based on a novel D-A type [3]rotaxane, was synthesized. The molecular elevator is capable of performing well defined mechanical movements under the actions of external inputs.