| Cyclodextrin (CD), as a typical of the second generation of supramolecular host, is of great significance to the development of supramolecular chemistry. During the study, we found that the huge molecular volume, special structure, and good crystallinity, make CD very suitable to build a molecule-ion aggregation and study the molecule-ion interactions.In this dissertation, powder X-ray diffraction (PXRD) was used to discuss the host-guest interaction in cyclodextrin (CD) chemistry, especially the influence of molecule-ion interaction on the PXRD spectra of adducts. A series of molecule-ion adducts of β-cyclodextrin (β-CD) were prepared and characterized using many modern analyses methods to look in the molecule-ion interaction and the decomposition behaviors. The results help us have a better understanding of the form, influence factors and its potential application of the molecular-ion interaction, and have important theoretical and practical significance in the development of supramolecular chemistry.(1) Several groups of adducts formed by β-CD and inorganic salts were prepared, and PXRD spectra of them were obtained and analyzed on the basis of the molecule-ion interactions between CDs and inorganic ions. Several influence factors of the PXRD spectra of CD complexes were summarized.(2) A molecule-ion adduct of β-CD and SA was prepared. The adduct was characterized using Fourier transform infrared spectroscopy, PXRD, differential thermogravimetric analysis, gas chromatography coupled to time-of-flight mass spectrometry, and electrospray ionization mass spectroscopy. We found that a weak molecule-ion interaction was responsible for the difference in spectral properties in solid state and in aqueous solution as well as for the difference in thermal decomposition behavior between β-CD, SA and the adduct. The novelty and complexity of this interesting molecule-ion interaction was revealed by a redox reaction based on the data of gas chromatograph coupled to time-of-flight mass spectrometer and by the formation of the1:1(molar ratio) supramolecular ion complex, Na+-β-CD, based on its electrospray ionization mass spectrum.(3) The thermal pyrolysis behaviour of a complex of β-CD and potassium ferrioxalate (PF) was analyzed using gas chromatography coupled to time-of-flight mass spectrometry. Two rare inorganic ions:CO22+and O4+, neither of which was found in the cases of free β-CD and PF, were synchronously observed during the decomposition of the complex. Our observations led to proposed formation mechanisms of the ions, in which the structural transformation of a metastable intermediate ion (C2H4O3+) was employed to qualitatively explain our data. Besides, the formation, structure and magnetic property of the complex were evaluated carefully. First, XPS analysis indicates a decrease of electron densities of Fe (Ⅲ) ions in the presence of β-CD. We think that this is due to an effect of the noncovalent complexation between PF and βCD. This gives an indication on the effect of second sphere coordination of β-CD on the electronic structure of the Fe (Ⅲ) in the first coordination sphere. Second, structural changes in stacking modes and morphologies provide further support for the noncovalent complexation. For example, surface feature of the complex gives us an impression that both β-CD and PF are evenly dispersed with each other. Also, the complex presents a uniform sponge-like porous nanostructure with diameters of less than50nm. This seems to be an important reason for those changes that occurred in the thermal analysis. Finally, the result of magnetic experiments implies that the coordination compound PF upon complexation with β-CD will experience a gradual decrease in magnetization with the increase of magnetic fields. These observations have significant implications for a better understanding the importance of construction and deconstruction of a second sphere coordination in modifying the physical properties of a σ-coordination compound.(4) In the present work,β-CD was employed to form molecule-ion adducts with a series of inorganic salts, such as lithium chloride, sodium chloride, sodium nitrate, sodium phosphate and so on, in order to investigate whether there is a relation between the change of thermal behavior of β-CD and the presence and properties of inorganic salts. Our results indicated that all the adducted β-CDs decomposed earlier than free β-CD both under nitrogen atmosphere and in vacuum. In particular, significant changes in maximum decomposition temperature (Tm) and maximum decomposition rate (Vm) of β-CD upon adduct had a close connection with the nature of inorganic salts. For example, the effects of chlorides and sodium salts of oxyacids on Tm of β-CD decreased in the orders:CaCl2> LiCl> KCl> NaCl and Na3PO4> Na2CO3> NaNO3, respectively. Interestingly, the orders were in good accord with the effects of β-CD on the molar conductivities of the salt solutions. Furthermore, mass spectral data indicated that the thermal release behavior of the adducted products was quite different not only from one another but also from free β-CD based on comparisons of relative abundances of decomposed fragments at the same heating times. In conclusion, the difference in thermal responses of β-CD to a series of inorganic salts was explained by different contributions from different molecule-ion interactions between β-CD and ions in the salts to the formation processes of the adducts, since the change in surface morphology and crystal structure of β-CD after adduct was found to be associated with the presence and properties of the salts. We believe that the results obtained from this study provide a new understanding of how the nature of inorganic salts relates to the thermal degradation of a carbohydrate of the importance of construction and deconstruction of a second sphere coordination in modifying the physical properties of a σ-coordination compound.(5) The present work is devoted to an attempt to understand the effect of an inorganic salt such as ferric trichloride (FeCl3) on the carbonization and degradation of carbohydrates such as β-CD, amylose, and cellulose. Our data revealed two important observations. First, the presence of FeCl3led to the occurrence of a low carbonization temperature of373K. This is a rare phenomenon, in which carbonization improvement is present even if a small amount of FeCl3was added. Experimental results had provided evidence for the fact that a redox process was started during the low-temperature carbonization of β-CD, causing the reduction of FeCl3to ferrous chloride (FeCl3) by carbon materials formed in the carbonization process in air. Second, a molecule-ion interaction emerged between FeCl3and the carbohydrates in aqueous solution, resulting in a more effective degradation of the carbohydrates. Moreover, our results demonstrated that FeCl3played the role of a catalyst during the degradation of the carbohydrates in solution. We believe that the current work not only has a significant potential application in disposal of waste carbohydrates but also could be helpful in many fields such as environmental protection, biomass energy development, and inorganic composite nanomaterials. |
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