The molecular structures in solutions were predicted for a chiral copper(II) complex [Cu(R-mben)2]2+ [R-mben = N-(methylbenzyl)ethylenediamine] based on the circular dichroism (CD) spectra in an acetonitrile solution and a pyridine solution. Each CD spectrum was analyzed to obtain the spectral components, and the coordination geometry around the copper(II) ion was estimated to be square-pyramidal on the basis of the observed spectral components. The structures of twelve probable conformers were optimized by DFT computation, and the CD spectrum was predicted for each structure by the TD-DFT method. Then, comparing the observed CD data with the predicted CD data, the structures in solutions were estimated.
We have studied antioxidant reactions of vitamin E (α-tocopherol) with an aroxyl radical in several organic solvents (ethanol, diethyl ether, benzene, hexane, and heptane) by using a stopped-flow spectrophotometer. The reaction mechanism is electron-transfer followed by proton-transfer from vitamin E to the radical, and the rate constant (ks) decreases with increasing solvent-polarity. To clarify the reason for the solvent-polarity dependence, we calculated atomic charges of hydrogen atoms in the solvent molecules. A linear relationship between the ks values and the atomic charges was obtained except for the point of ethanol. The reason for the deviation in ethanol is that ethanol solvent has strong intermolecular hydrogen-bonding and is not easy to be reorganized. It was found that the reorganization energy of Marcus theory has an important influence on the ks value. As the solvent-polarity and the reorganization energy increase, the curvature of the potential curve increases and therefore the ks value decreases.
The crystal structure of the intermediate phase (3MgO·2CO2) of synthetic nesquehonite (MgO·3H2O) following heat treatment was solved by Monte Carlo simulation using powder X-ray diffraction data and was confirmed by Rietveld refinement. The phase is cubic with space group I4¯3m and cell constants of a = 8.516(13) Å. The unit cell consists of independent atoms such as magnesium, carbon, and two oxygen atoms. The magnesium atom is surrounded by six oxygen atoms in octahedral coordination, and four symmetrically identical MgO6 octahedra in a edge-sharing arrangement form an Mg4O17 block in the (100) planes of a unit cell. These Mg4O17 blocks share edges with other Mg4O17 blocks to form a framework structure. A CO3 triangle that exists on the three-fold axis connects three Mg4O17 blocks.