Multinuclear Solid-State NMR Investigation of Hexaniobate and Hexatantalate Compounds.
Multinuclear Solid-State NMR Investigation of Hexaniobate and Hexatantalate Compounds.
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DOI：
10.1021/acs.inorgchem.6b00345
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发表时间：
2016-06
影响因子：
4.6
通讯作者：
G. Deblonde;Cristina Coelho-Diogo;A. Chagnes;G. Cote;Mark E. Smith;J. Hanna;D. Iuga;C. Bonhomme
中科院分区：
文献类型：
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作者：
G. Deblonde;Cristina Coelho-Diogo;A. Chagnes;G. Cote;Mark E. Smith;J. Hanna;D. Iuga;C. Bonhomme
这项工作确定了潜在的固态核磁共振技术探测质子，碱，铌环境中Lindqvist盐。本文用固体静态和魔角自旋（MAS）核磁共振方法研究了Na_7HNb_6O_（19）·15H_2O（1）、K_8Nb_6O_（19）·16H_2O（2）和Na_8Ta_6O_（19）·24.5H_2O（3）在强磁场和弱磁场（16.4T和19.9T）下的结构。(1)H MAS NMR是一种方便、直观的方法，可以用来区分质子化和非质子化的AxH_（8-x）M_6O_（19）·nH_2 O（A =碱金属离子; M = Nb，Ta）。（93）在不同磁场和MAS旋转频率下对1.在六铌酸盐团簇中，NbO_5 O μ_2H位的贡献首次与NbO_6位的贡献区分开来. MAS下得到的共振强增宽的解释相结合的化学位移各向异性（CSA）与四极效应，并通过使用广泛的拟合线的形状。为了获得所有NMR参数（CSA和四极）的最高准确度，在16.4 T下记录样品1的静态模式下的（93）Nb WURST QCPMG光谱。结合文献中可获得的XRD数据（即，NbO_5 O μ ~ 2 H位的占有率）。1的1D（23）Na MAS和2D（23）Na 3QMAS NMR研究显示了几个不同的钠位点。的网站的多重性再次比较以前获得的单晶X-射线衍射（XRD）研究的结构细节。3的（23）Na MAS NMR研究证实存在与XRD预测的10个钠位点一致的大得多的钠位点分布。最后，通过多核MAS NMR（（1）H，（23）Na，和（93）Nb）研究了Nb/Ta取代对1的影响。
This work determines the potential of solid-state NMR techniques to probe proton, alkali, and niobium environments in Lindqvist salts. Na7HNb6O19·15H2O (1), K8Nb6O19·16H2O (2), and Na8Ta6O19·24.5H2O (3) have been studied by solid-state static and magic angle spinning (MAS) NMR at high and ultrahigh magnetic field (16.4 and 19.9 T). (1)H MAS NMR was found to be a convenient and straightforward tool to discriminate between protonated and nonprotonated clusters AxH8-xM6O19·nH2O (A = alkali ion; M = Nb, Ta). (93)Nb MAS NMR studies at different fields and MAS rotation frequencies have been performed on 1. For the first time, the contributions of NbO5Oμ2H sites were clearly distinguished from those assigned to NbO6 sites in the hexaniobate cluster. The strong broadening of the resonances obtained under MAS was interpreted by combining chemical shift anisotropy (CSA) with quadrupolar effects and by using extensive fitting of the line shapes. In order to obtain the highest accuracy for all NMR parameters (CSA and quadrupolar), (93)Nb WURST QCPMG spectra in the static mode were recorded at 16.4 T for sample 1. The (93)Nb NMR spectra were interpreted in connection with the XRD data available in the literature (i.e., fractional occupancies of the NbO5Oμ2H sites). 1D (23)Na MAS and 2D (23)Na 3QMAS NMR studies of 1 revealed several distinct sodium sites. The multiplicity of the sites was again compared to structural details previously obtained by single-crystal X-ray diffraction (XRD) studies. The (23)Na MAS NMR study of 3 confirmed the presence of a much larger distribution of sodium sites in accordance with the 10 sodium sites predicted by XRD. Finally, the effect of Nb/Ta substitutions in 1 was also probed by multinuclear MAS NMR ((1)H, (23)Na, and (93)Nb).