Studies Of Catenanes And Photo-responsive Host-guest System Based On Cryptands

As one kind of the basic interlocked structures, catenanes have acquired more and more attentions not only because of their topologic interesting but also due to their potential applications in molecular electronics and nanotechnology. Various kinds of catenanes have been successfully constructed by template-directed protocols.We synthesized a series of novel catenanes based on different kinds of cryptands, benefited from the good template effect between the cryptands and the paraquat derivatives. In these structures, bisparaquat cyclophane rings are mechanically interlocked with three-dimensional cryptand "molecular cage", which is different from ordinary catenanes composed of mechanically interlocked two-dimensional rings. Besides characterizing these catenanes by different method, we studied their movement characteristic in solution, and for the first time we explored the self-assembly behavior of catenanes in solid state using single crystal data. It's found that the novel catenanes have many differences compared with the traditional donor/acceptor catenanes:1) The yields of these catenanes were impressive considering the steric effect from three-dimensional cryptands in the ring-close step, which should benifited from the high association constants between the cryptands and paraquat derivatives; 2) Compared with the traditional donor/acceptor catenanes based on crown ethers, the structure of these catenanes were more compact, and the interactions between the host and guest components were stronger. Besides theπ-donor/π-acceptor stacking and C-H…πinteractions, there were more hydrogen bonds interaction abundantly offered by the three-dimensional structure of the cryptands. And the hydrogen bonds interaction should play a more significant role in the formation and stabilization of the catenanes; 3) It's found that the energy barrier, which the interlocked components'movements should overcome, increased a lot as a result of the stronger interactions between the host and guest components, which will restrict the flexible of these catenanes; 4) From the studies of their crystal structures, some interesting supramolecular structures were found, such as catnanes "captured" H2O molecules in their cavity, catenane dimer and supramolecular main-chain-ploycatenane structures; 5) The tiny change in catenane structures would make a huge difference in their self-assembly processes. And it's found incorporated aromatic rings and carbonyl group would increase their self-assembly approaches to form high-level structures.The second part of my work involved constructing a new photo-responsive host-guest system. A new cryptand was efficient synthesized, which can be well controlled between cis and trans isomers by irradiating different wavelength light or being heated. It's found tha this cryptand exhibit an ON-OFF binding ability with 2,7-dimethyldiazapyrenium salt derivative (DAP):this cryptand bound the diazapyrenium salt derivative at cis isomer only, which have been well demonstrated by various methods. The operation mechanism should be: the cis-trans transform of azobenzene unit in the cryptand changed the cavity of the host, which would result in the change of association ability between the host and the guest. The fluorescence properties of DAP molecule endued this system with detectable output fluorescence signals, which would make the monitoring of the photo-responsive system's operation more convenient. The new effective photo-responsive host-guest system will benefit us to make much more interesting complicated photo-responsive supramolecular systems. We also reported a photocontrolled bistable pseudorotaxane based on this system.