Electron Localization of Polyoxomolybdates with ε-Keggin Structure Studied by Solid-State 95Mo NMR and DFT Calculation
Electron Localization of Polyoxomolybdates with ε-Keggin Structure Studied by Solid-State 95Mo NMR and DFT Calculation
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DOI：
10.1021/jp409969g
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发表时间：
2014-04-03
影响因子：
2.9
通讯作者：
Nishimura, Katsuyuki
中科院分区：
文献类型：
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作者：
Iijima, Takahiro;Yamase, Toshihiro;Nishimura, Katsuyuki
本文报道了用固体Mo-95核磁共振和密度泛函理论计算研究了具有epsilon-Keggin结构的多钼酸盐的电子局域化。所研究的多钼酸盐是[Me_3NH](6)[H_2Mo_(12)O_(28)(OH)(12){MoO_3}(4)]中心点2H(2)O(1)的碱性epsilon-Keggin晶体，晶体具有无序的[PMo12O36(OH)(4){La(H2O)(2.75)Cl-1.25}(4)]center点27H(2)O(2)的{epsilon-Mo-12}核。顺磁性Keggin晶体[H_2Mo_(12)O_30(OH)(10){Ni(H_2O)(3)}(4)]中心点14H(2)O(3)。在中强磁场(9.4和11.7T)和超强磁场(21.8T)下测量了这些样品的Mo-95静态核磁共振谱。通过光谱模拟和量子化学计算，估算了Mo-95的化学位移和四极相互作用的核磁共振参数。通过对1的分析发现，2虽然{epsilon-Mo-12}核是无序的，但其中的8个d(1)电子并不完全局域在4个Mo-Mo键上。此外，对于3，d(1)电子被定域以形成Mo-Mo键，而未成对的电子也几乎定域在顺磁性的Ni-II离子上。
We report electron localization of polyoxomolybdates with epsilon-Keggin structure investigated by solid-state Mo-95 NMR and DFT calculation. The polyoxomolybdates studied are the basic epsilon-Keggin crystals of [Me3NH](6)[H2Mo12O28(OH)(12){MoO3}(4)]center dot 2H(2)O (1), the crystals suggested to have a disordered {epsilon-Mo-12} core of [PMo12O36(OH)(4){La(H2O)(2.75)Cl-1.25}(4)]center dot 27H(2)O (2), and the paramagnetic Keggin crystals of [H2Mo12O30(OH)(10){Ni(H2O)(3)}(4)]center dot 14H(2)O (3). The spectra of Mo-95 static NMR of these samples were measured under moderate (9.4 and 11.7 T) and ultrahigh magnetic fields (21.8 T). From spectral simulation and quantum chemical calculation, the NMR parameters of the chemical shift and quadrupole interactions for Mo-95 were estimated. By the analysis based on the result for 1, it was found for 2 that although the {epsilon-Mo-12} core is disordered, the eight d(1) electrons in it are not completely localized on four Mo-Mo bonds. Furthermore, it was shown for 3 that the d(1) electrons are localized to make the Mo-Mo bonds, while the unpaired electrons are also almost localized on the paramagnetic Ni-II ions.