Molecule-ion interaction and its effect on electrostatic interaction in the system of copper chloride and ß-cyclodextrin.

The present work was devoted to an experimental investigation of the molecule-ion interaction between copper chloride (CuCl(2)) and ß-cyclodextrin (CD) and its effect on the electrostatic interaction between Cu(2+) and Cl(-) ions. Our results gave an explicit description of the mutual effect between the interactions. First, the molecular arrangement and surface feature of ß-CD experienced a fundamental structural change after interaction with Cu(2+) and Cl(-) ions, which was ascribed to a good separation of Cu(2+) from Cl(-) ions in ß-CD matrix. Second, arguments based on electronic structural analysis provided a direct indication of the change in charge density distributions of Cu(2+) and Cl(-) ions in the presence of ß-CD. Third, the actual occurrence of a second signal in the course of water release at a higher temperature suggested that the Cu(2+) ions were trapped in the form of hydrates in the crystal interstice of ß-CD molecules. Fourth, comparison of the mass spectra indicated that the thermal decomposition of ß-CD in the presence of CuCl(2) produced a series of interesting molecular ions: C(3)H(2)OH(+), C(4)H(3)OH(+), C(5)H(4)OH(+), and C(7)H(6)OH(+). We consider that this study is helpful in providing a new approach to the evaluation of the extent of the mutual effect between an inorganic salt and an organic molecule.

Molecule-ion interaction and its effect on coordination interaction.

The present work revealed the presence of the molecule-ion interaction between ethylenediaminetetraacetic acid disodium salt (Na(2)H(2)EDTA) and ß-cyclodextrin (CD) on the basis of observable changes in crystal patterns and thermal behaviors before and after interaction. Results from electric conductivity measurements confirmed this presence and showed that the extent of the molecule-ion interaction was associated with the concentration of ß-CD. More importantly, the molecule-ion interaction led to a decreased coordination interaction of Na(2)H(2)EDTA and copper chloride, and this decrease exhibited a concentration dependence of ß-CD. Similar phenomena were also observed in the case of several analogs of Na(2)H(2)EDTA by UV-vis spectroscopy. A possible explanation was proposed on the basis of the hypothesis that there was a competitive relationship between the molecule-ion interaction and the coordination interaction. Further, nuclear magnetic resonance measurements provided important information on the difference in interaction modes of ß-CD with H(2)EDTA(2-) and [Cu(EDTA)](2-). We are of the opinion that the results would provide a significant bridge between coordination chemistry and supramolecular chemistry and help us further understand factors related to different interactions in multicomponent systems.

Important effects of lithium carbonate on stoichiometry and property of the inclusion complexes of polypropylene glycol and ß-cyclodextrin.

The present work reveals a significant influence of lithium carbonate (Li(2)CO(3)) on stoichiometry, yield, spectral property, and thermal behavior of the inclusion complex formed by polypropylene glycol (PPG) and ß-cyclodextrin (CD). First, the presence of Li(2)CO(3) in aqueous solution leads to the formation of an inclusion complex PPG-(ß-CD)(6), which is completely different from that precipitated from pure water. This finding is supported by the result of a similar experiment in the case of lithium chloride, demonstrating that the self-assembling behavior of PPG, a flexible oligomer, and ß-CD, a rigid oligomer, in solution can be mediated by additions of the lithium salts. Second, powder X-ray diffraction patterns indicate that the lithium salts in solution play a considerable role in fabricating three-dimensional structures of the complex. Third, the difference in stoichiometry and microstructure of the complexes precipitated from different media is reflected by the difference of their thermal properties. Finally, the results of viscosity, surface tension, and conductivity measurements provide positive support on the effect of the lithium salts on the physical property of PPG solution. Taken together, these observations provide a novel framework for understanding functions of inorganic salts in designing and constructing supramolecules.

Noncovalent interaction of polyethylene glycol with copper complex of ethylenediaminetetraacetic acid and its application in constructing inorganic nanomaterials.

In this study, we try to answer a fundamental question: what is the consequence of the noncovalent interaction between a polymer and a coordination compound? Here, polyethylene glycol (PEG-4000, PEG-b) and copper complex of ethylenediaminetetraacetic acid (H(2)CuY) were employed to solve this problem. A novel adduct (CEP) between H(2)CuY and PEG-b was prepared. Our results indicated several interesting findings. First, the introduction of H(2)CuY had no effect on the stacking structure of PEG-b but led to a large change in surface structure of the polymer. Second, there was a significant difference (117 K) in the maximum degradation temperature between the PEG and the CEP, suggesting that the noncovalent interaction can drastically improve the thermal stability of the PEG. Third, sintering experiments showed that H(2)CuY and CEP produced completely different decomposition products. The former formed Cu crystals in nitrogen and CuO in air, but the latter generated Cu and CuCl crystals with good crystallinity, respectively. Finally, three independent measurements: viscosity, conductivity and nuclear magnetic resonance in solution, provided useful information and insights from both sides of the noncovalent interaction. Probable interaction mechanisms and interaction sites were proposed. We consider that the current research could create the foundation for a new understanding of how the noncovalent adduct interaction between a metallic complex and a polymer relates to the change in physical and chemical properties of the adducted components.

Formation, characterization, and thermal degradation behavior of a novel tricomponent aggregate of beta-cyclodextrin, ferrocene, and polypropylene glycol.

A tricomponent aggregate PPG-Fc-beta-CD formed by polypropylene glycol (PPG), ferrocene (Fc), and beta-cyclodextrin (beta-CD) was obtained and characterized by a series of physical methods, such as (1)H nuclear magnetic resonance, flame atomic absorption spectrometry, high performance liquid chromatography, UV-vis absorption spectroscopy, thermogravimetry, and gas chromatography coupled to time-of-flight mass spectrometry. First, the tricomponent aggregate exhibited a component ratio of 1:28:32 (PPG/Fc/beta-CD) in the solid state, and showed a completely different order in thermal stability when compared with beta-CD: under a nitrogen atmosphere, beta-CD > PPG-Fc-beta-CD, and in a vacuum, PPG-Fc-beta-CD > beta-CD. Second, the appearance of two peculiar points p and q at the end of TG curve of the aggregate gave a strong impression that the degradation rate further increased after the sharp decomposition of the aggregate reached point p and the amount present in the residual fraction at point q about 780.0 K was lower than 1%, both of which were rather different from those reported previously. This finding implied that the molecular assembly resulting from the binding interaction among Fc, PPG, and beta-CD induced more efficiently the degradation of each of them. Third, an interesting phenomenon was found that the order of thermal release of the three assembled components in PPG-Fc-beta-CD was Fc > beta-CD > PPG. Results of this study provide some insight into an initial attempt to construct a supramolecule among a polymer, a coordination compound, and an organic compound.

Meaningful differences in spectral performance, thermal behavior, and heterogeneous catalysis between ammonium molybdate tetrahydrate and its adduct of beta-cyclodextrin.

A novel molecule-ion adduct of ammonium molybdate tetrahydrate (AMT) with beta-cyclodextrin (CD) was prepared in this work. Significant differences in spectral properties between AMT and the adduct AMT-beta-CD were observed by a series of experimental probes, such as powder X-ray diffraction, Fourier transformation infrared spectroscopy, and Raman spectroscopy. Field emission scanning electron microscopy showed that, although the crystal growth of AMT-beta-CD was dominated by the molecular stacking of AMT, the size and morphology of the adduct were rather different from those seen in free AMT. The difference in stacking forms was attributed to the contribution of the molecule-ion interaction between AMT and beta-CD. A drastic improvement in thermal stability of AMT and beta-CD after adduct formation was observed by thermogravimetry analysis, which was confirmed by controlled sintering measurements. This revealed that the adduct interaction between them played an important role in mediating the thermal decomposition process of the adducted components. Furthermore, our results indicated that AMT and its adduct had a different performance in the catalytic desulfurization of thiophene and its derivatives. The fact that the catalytic efficiency of AMT was decreased after adduct formation implied there was a complexation between AMT and beta-CD. Besides, several unusual molecular ions--NH(3)(+), NH(2)(+), and NH(+)--were simultaneously found with gas chromatography coupled to time-of-flight mass spectrometry of free AMT.