Functionalized Rotaxane Molecular Shuttles Based On Crown Ether Derivatives

With the development of supramolecular chemistry, the field of molecular machines based on supramolecular self-assembly has attracted much attention during the past few decades. Molecular shuttle based on rotaxane, as a type of molecular machines, composed of a circular component and a dumbbell-shaped component, which penetrates the internal cavity of the circular component. Two stoppers on the ends of the dumbbell-shaped component can prevent the dissociation of the circular one. Under external specific stimuli, the circular component can move back and forth along the thread of the dumbbell-shaped component without separation. Molecular shuttle, which is one of ideal systems for the study of intermolecular weak interactions and their conversions provides a new model system for the research of important physical and chemical processes between the components, for example, energy transfer and electron transfer etc.The emergence of crown ether, an important kind of host compounds, is the milestone in the field of supramolecular chemistry. Now, the fields of molecular machines based on crown ether and its derivatives and highly complicated molecular self-assembly have made great progress.The main contents and results of this dissertation are generalized as follows:In chapter1, the recent progress of molecular machine is summarized. The definition and three species (rotaxane, pseudorotaxane, and catenane) of molecular machine were intrduced and illustrated by examples. Driving forces of switchable molecular machine, like chemical energy, electrochemical energy, light energy, and others, were reviewed illustrationally. The identifications of movement of molecular machine, like NMR spectra, ultraviolet-visible absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and induced circular dichroism spectra were generalized. In addition, the potential application of molecular machine in such areas as molecular nanovalve, organic catalyst, organic gel, supramolecular polymer and treatment of poisoning were also elaborated.In chapter2, a multi-state [2]rotaxane molecular shuttle R1based on a dithienylethene-functionalized crown ether and the dumbbell-shaped reference compound D1were designed and synthesized successfully. The structure and spectral properties of the target rotaxane compound R1were investigated using NMR spectra, UV-vis spectra and fluorescence spectra. It can be concluded that the shuttling movement of the macrocycle between two recognition sites in R1can be achieved under external acid-base stimuli. Furthermore, the interactions between photochromic unit and the4-morpholin-naphthalimide fluorophore are able to be adjusted by external chemical and photochemical stimuli.In chapter3, a novel ferrocene functionalized crown ether C2, a bistable [2]rotaxane molecular shuttle R2, in which the ferrocene functionalized crown ether is the macrocycle and the dumbbell-shaped reference compound D2were designed and prepared successfully. The structure and spectral properties of the target rotaxane compound R2were investigated using NMR spectra, UV-vis spectra and fluorescence spectra. These experiments have showed that the shuttling movement of the macrocycle between two recognition sites in R2and the PET (photoinduced electron transfer) process occurring between ferrocene units and the4-morpholin-naphthalimidc fluorescent stopper, can be adjusted not only by acid-base stimuli but also addition-removal of the fluoride anion. Most importantly, the movement of the macrocycle result in remarkable, highcontrast fluorescent intensity changes which can be identified by naked eyes.In chapter4, a novel ferrocene-functionalized [2]rotaxane R3with two fluorophores as stoppers were designed and synthesized successfully. The structure and spectral properties of the target rotaxane compound R3were investigated using NMR spectra, UV-vis spectra and fluorescence spectra. It has been shown that, by introducing two ferrocene units into the macrocycle component of R3, the fluorescence of two fluorescent stoppers, namely, the anthracene fluorophore and the4-morpholin-naphthalimide fluorophore, can be changed in an alternate mode by an adjustable, distance-dependent PET (photoinduced electron transfer) process that occurs between the ferrocene electron donors and each of the two fluorophores.In chapter5, a novel star-shaped zinc porphyrin cored [5]rotaxane R4with four rotaxane arms was designed and synthesized successfully. The structure of the target rotaxane compound R4and shuttling movement of four macrocycles were investigated using NMR spectra thoroughly. The introduction of the zinc porphyrin core enabled the [5]rotaxane to have a fixed shape and symmetrical structure, and the simultaneous shuttling motion of four macrocycles can be driven by external acid-base stimuli. This kind of topological structure exhibits important potential in the design and construction of highly symmetrical and large sophisticated assemblies.In chapter6, two novel [2]rotaxane R5and R6which were stoppered by a cholesterol group and long carbon chains respectively were designed and synthesized successfully. Their structure were confirmed using NMR spectra. Now, the related work is in progress.In chapter7, conclusion.