Formation, Host-guest Interaction And Sensing Applications Of Ruthenium Tetracarboxylic Acid And Aminocyclodextrin Ion Associations

The aromatic chromophore, perylene-3,4,9,10-tetracarboxylic acid bisimide ?PBI? has received a great deal of attention during the last few decades owing to their exceptional optical and electronic properties, such as high fluorescence quantum yields, good photochemical, electrochemical stability, and unique oxidation-reduction that are favorable for application in different areas of organic photoelectronics, fluorescence chemical/biochemical sensors and single-molecule spectroscopy. However, the inherent poor solubility of PBI derivatives in commonly found solvents, especially in water, they tend to form non-fluorescent ?-? stacks, which greatly limits biological applications. Thus preparing water soluble and highly fluorescent PBI derivatives is not only one of the important technical problems to be solved, but also a great'challenge to the scientist working in the field. To increase the aqueous solubility, the side-group functionalization of PBI derivatives, mainly through the covalent attachment of substituents at the diimide positions or the "bay region" has become a popular strategy.The strategy, however, as mentioned for enhancing their solubility, is often inevitably realized via complicated organic synthesis, and thereby, it would be of interest if noncovalent interactions such as hydrogen bonding, ?-? stacking, van der Waals interaction, host-guest interaction, electrostatic interaction, dipole-dipole interaction, coordination interaction and so on could be utilized to improve the water solubility of the derivatives, and realize their functions in aqueous phase.Cyclodextrins ?CDs? is a family of cyclic oligosaccharides that are composed of six to eight a-D-glucopyranoside units in a ring linked by a-1,4-glycosidic bonds. The CDs possess a hydrophilic exterior surface and hydrophobic interior cavity on the truncated cone. It is the cavity that makes CDs become a group of organic hosts for the inclusion of some organic molecules in aqueous phase. In addition, the hydroxyl groups presenting at different positions can be selectively converted into other desired functional structures, and the derivatives as obtained may be further used for constructing diverse supramolecular architectures.The attractive advantages of CDs and those of PBI have inspired us to make a hypothesis that is combination of CDs and PBI via a noncovalent method would lead to weakening of the strong ?-? interaction between PBI units, resulting in increase in the water solubility of the chromophore which is the basis for being used in aqueous phase. On the basis of the proposal and the previous work of our group, a water-soluble complex of PBI and CDs was constructed by using perylene tetracarboxylic acid ?PTCA? and 6-deoxy-6-amino-?-CD ??-CDNH2? as the reactants under the aid of electrostatic interaction between carboxyl and amino in aqueous phase. Unlike other PTCAbisimide derivatives, preparation of the ionic complex of PTCA/??-CDNH₂?₄ is simple and avoids complicated synthetic burden. Interestingly, PTCA/??-CDNH₂?₄ was found to undergo a remarkable structural change in the presence of water that result in a yellow-to-green color transition. Furthermore, introduction of the bulky hydrophilic ?-CD endows the ionic complex rich host-guest chemistry. Thus it not only realized sensitive and selective detection of toxic phenolic compounds, especially phenol, in water but also employed as dispersed phase obtaining the stable gel emulsion through the host-guest interaction between PTCA/??-CDNH₂?₄ and 2DFc. Besides, we hope to produce a fluorescent complex containing ferrocenyl group at the oil-water interface by the driving force of the host-guest interaction. The research work mainly consists of the following two sections.In the first section, on the basis of proton transfer in aqueous phase, we prepared a water-soluble and highly fluorescent ionic complex of PTCA and ?-CDNH2 and studied its fluorescence behavior. It was found that the fluorescence emission of the complex is sensitive and selective to the presence of trace amount of toxic phenolic compounds, in particular phenol, which is crucial for water quality control. The detection limit ?DL? of the method to the analyte is-0.03 ?M, a lowest value reported in literatures for similar techniques. Interestingly, the detection at an unprecedented subnanogram ?DL,-0.12 ng/cm2? level can also be conducted in a visualized manner, which may provide a simple and low-cost protocol for on-site and real-time detection of the analyte. Furthermore, introduction of methanol into the aqueous solution of the complex resulted in aggregation as indicated by solution color change, which proved by transmission electron microscopy and dynamic light scattering studies. UV-vis, and fluorescence studies furtherly uncovered the H-packing nature of the structure of the aggregate. And then we find the complex is humidity sensitive in dry state, and its color changes from bright yellow to bright green when exposed to wet vapor. X-ray diffraction suggests that swelling of the aggregate, which must be a result of water-promoted increase in the interplanar spacing.In the second section, considering the host-guest interaction between the building block of cyclodextrin in PTCA/??-CDNH₂?₄ and the ferrocenyl group. A new ferrocene derivative 2DFc, containing two cholesteryl units, putting diethylenetriamine unit as a linker, was specially designed and prepared. Studying on the gelation behaviors of 2DFc shows that the ferrocene derivative forms stable gels only in cyclohexane. Besides,2DFc, the aqueous solution of PTCA/??-CDNH₂?₄ and cyclohexane which were employed as stabilizer, the continuous phase and the dispersed phase, respectively. It can obtain stable gel emulsion when the volume ratio of cyclohexane to water reaches 3:7 or 2:8. Compared with the control experiment, it is concluded that the host-guest interaction between 2DFc and PTCA/??-CDNH₂?₄ in the oil-water interface is one of the driving forces for the formation of the two kinds of gel emulsion systems. And we hope to obtain a fluorescent complex containing ferrocenyl group at the oil-water interface through the host-guest interaction.