Functional Molecular Machines Based On Crown Ether Derivatives

Crown ethers and their derivatives act as very important host compounds in the fields of suparmolecular chemistry and molecular recognition. The reversible complexation between the dialkylammonium moiety and the dibenzo[24]crown-8 (DB24C8) macrocycle, as well as their acid-base switching properties in solution, have been widely studied and harnessed to construct molecular elevator, molecular muscles and molecular antenna. In this thesis, dibenzo[24]crown-8 was modified with several functional groups, such as photochromic groups and electron-rich groups, and their potential as components of molecular machines was investigated.The main contents and results are generalized as follows:In chapter 1, an overview of the research background of molecular machinery systems and their potential applications are presented.In chapter 2, a dibenzo-24-crown-8 with a photochromic dithienylethene (DTE) unit was synthesized and its photochromic properties were thoroughly studied. A thread-shaped molecule with a fluorescent naphthalimide (NA) designed as a guest compound for DTE-24C8 was prepared. The threading-dethreading properties between the crown ether derivative and the fluorescent thread compound under chemical stimuli, which can affect the energy transfer between the two moieties, were investigated.In chapter 3, a multicomponent molecule DTE-(24C8)2, in which two dibenzo-24-crown-8 units are separated by a photochromic dithienylethene bridge, was designed and synthesized. Its photochromic properties was studied using UV-Vis absorption spectroscopy. The compexation between DTE-(24C8)2 and a thread-shaped component containing two dialkylammonium moieties was also studied. Efforts towards a lockable [3]rotaxane with fluorescent outputs have been made in this chapter.In chapter 4, a photoactive molecule A-(24C8)2, which contains two dibenzo-24-crown-8 units bridged by an anthracene moiety, was prepared. The structure was characterized by 1H NMR,13C NMR and HR-ESI spectrometry. Its photo-dimerization upon 365 nm UV light irradiation, accompanied by a decrease in fluorescent intensity, was observed.Chapter 5 is the conclusion.