期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 124, 期 9, 页码 1951-1957出版社
AMER CHEMICAL SOC
DOI: 10.1021/ja012190z
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Three new molybdenyl iodates, KMoO3(IO3) (1), RbMoO3(IO3) (2), and CsMoO3(IO3) (3), have been prepared through the hydrothermal reactions Of MoO3 with AlO4 (A = K, Rb, or Cs) at 180 degreesC. These compounds are isolated as nearly colorless, air-stable crystals. Single-crystal X-ray diffraction experiments reveal that 1 possesses a corrugated layered structure constructed from molybdenum oxide chains that are bridged by iodate anions. The puckering of the layers is caused by the alignment of bent molybdenyl (MoO22+) groups along one side of the molybdenum oxide chains. The K+ cations separate these layers from one another and serve to balance charge. In contrast, compounds 2 and 3, which are isostructural, form three-dimensional structures with small cavities filled with Rb+ or Cs+ cations. The differences between the structures of 1 and those of 2 and 3 are due to rotation of the molybdenyl units as translation occurs down the molybdenum oxide chains in order to accommodate the increased size of the Rb+ and Cs+ cations. This rotation allows for the iodate anions to bridge the molybdenum oxide chains in an additional dimension, creating a three-dimensional network structure. Furthermore, while I crystallizes in a centrosymmetric space group, 2 and 3 crystallize in polar space groups. Second-harmonic generation measurements on 2 and 3 show large responses of 400 x alpha-quartz. Differential scanning calorimetry measurements demonstrate that 2 and 3 are thermally stable to 494 and 486 degreesC, respectively. UV-vis diffuse reflectance spectra of these compounds show a high degree of transparency from 1 to 3 eV and a band gap of 3.1 eV.
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