Study On Synthesis And Properties Of Molecular Shuttle Based On Urea And Phosphine Oxide

Molecular machine is a hot research topic in supramolecular chemistry which has attracted more and more attention for the past decades. There are both opportunities and challenges in this field. Molecular shuttle, a kind of rotaxane, which can be switched by external stimuli represents the archetype of molecular machine. It is the most simple and ideal model system to study the controllable properties of molecular machine. Molecular shuttle is made up of a cycle component and a dumbbell-shaped component. On both ends of the dumbbell-shaped component are there the stoppers, which are big enough to prevent the cycle component from sliding down. More than one recognition sites can be found on the dumbbell-shaped component. There are some kinds of weak interactions between the cycle component and the recognition site on the dumbbell-shaped component. Under external stimuli, relative movement happens between the cycle component and the dumbbell-shaped component, including sliding and rotating. There are two important research directions for rotaxane type molecular machine including the discovery of new recognition sites on the dumbbell-shaped component and the development of new cycles.According to the above research frame, the research content of this dissertation mainly includes the following aspects:In chapter 1, the important position of molecular machine in supramolecular chemistry is summarized, and molecular machines that are widely studied (pseudorotaxane type of molecular machine, rotaxane type of molecular machine, catenane type of molecular machine) are illustrated. Then we introduced the driving factors that switch the molecular machines "functioning" including pH regulation, ion regulation, electrochemical regulation, configuration regulation, optical regulation and solvent change regulation. Finally, the potential applications of molecular machine are introduced in small molecule gel, supramolecular catalysis, pesticide detoxification, drug delivery, and simulation peptide synthesis.In chapter 2, a switchable three-station rotaxane based molecular shuttle with phosphine oxide, dibenzylammonium, and urea functional groups was developed, where the macrocycle can be easily switched between three different binding sites along the rotaxane thread by the addition of acid/base or anions resulting in three stable states. Phosphine oxide is shown to be a potential recognition unit for rotaxane based molecular shuttles and plays an important role as one of three "stations", allowing the design of a new class of molecular shuttles.In chapter 3, we designed a molecular shuttle based on phosphine oxide, dibenzylammonium, and urea functional groups. Here we change the joint order of these three recognition sites compared to the molecular shuttle in chapter 2, and the urea recognition site is moved to the middle, forming a new molecular shuttle. pH regulation and ion regulation are used to achieve the movement of the macrocycle through one side to another.1H NMR and 2D ROESY NMR give a powerful evidence for the movement of the macrocycle.In chapter 4, we designed and synthesized a macrocycle containing ferrocene group, and the macrocycle was used for the synthesis of molecular shuttle. The designed molecular shuttle contains two recognition sites and one of the stoppers is anthracene group which possesses unique fluorescent properties. pH regulation and anion regulation are used to drive the movement of the macrocycle. In the process of the regulation, the photoinduced electron transfer (PET) process between ferrocene group and anthracene group was affected, so different fluorescence responses can be detected.In summary, this dissertation has synthesized molecular shuttles based on urea and phosphine oxide. And the switchable properties of these molecular shuttles were studied. We synthesized a kind of molecular shuttle with fluorescent response, and then studied its response properties, which is significant for further research.