Investigating the vanadium environments in hydroxylamido V(V) dipicolinate complexes using 51V NMR spectroscopy and density functional theory.
Investigating the vanadium environments in hydroxylamido V(V) dipicolinate complexes using 51V NMR spectroscopy and density functional theory.
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DOI：
10.1021/ic7012667
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发表时间：
2007-09
影响因子：
4.6
通讯作者：
K. Ooms;S. E. Bolte;Jason J. Smee;B. Baruah;D. Crans;T. Polenova
中科院分区：
文献类型：
--
作者：
K. Ooms;S. E. Bolte;Jason J. Smee;B. Baruah;D. Crans;T. Polenova
利用（51）V魔角自旋固体NMR、SSNMR、光谱学和量子化学DFT计算，我们表征了一系列通式为VO（dipic）（ONR 1 R2）（H2O）的8个羟胺基吡啶二甲酸钒（V）配合物的化学位移和四极耦合参数，其中R1和R2可以是H、CH 3或CH 2CH 3。选择这类钒化合物进行研究是因为它们的七配位钒原子，其几何结构有限（51）V SSNMR数据。此外，一系列系统的化合物具有不同的电子性质，并允许配体取代的NMR参数的影响进行研究。四极耦合常数C（Q）很小，为3.0-3.9 MHz，但随配体取代度的变化而变化。在固体状态下的化学位移张量是敏感的，在两个羟基酰胺取代基和dipic配体，在溶液中的各向同性化学位移没有观察到的敏感性的变化。化学位移张量跨度约为1000 ppm，几乎轴对称。基于化学位移张量的DFT计算，磁屏蔽各向异性的最大贡献者之一是沿沿着V=O键具有显著钒d（z）2特征的占据分子轨道。
Using (51)V magic angle spinning solid-state NMR, SSNMR, spectroscopy and quantum chemical DFT calculations we have characterized the chemical shift and quadrupolar coupling parameters of a series of eight hydroxylamido vanadium(V) dipicolinate complexes of the general formula VO(dipic)(ONR1R2)(H2O) where R1 and R2 can be H, CH3, or CH2CH3. This class of vanadium compounds was chosen for investigation because of their seven-coordinate vanadium atom, a geometry for which there is limited (51)V SSNMR data. Furthermore, a systematic series of compounds with different electronic properties are available and allows for the effects of ligand substitution on the NMR parameters to be studied. The quadrupolar coupling constants, C(Q), are small, 3.0-3.9 MHz, but exhibit variations as a function of the ligand substitution. The chemical shift tensors in the solid state are sensitive to changes in both the hydroxylamide substituent and the dipic ligand, a sensitivity which is not observed for isotropic chemical shifts in solution. The chemical shift tensors span approximately 1000 ppm and are nearly axially symmetric. On the basis of DFT calculations of the chemical shift tensors, one of the largest contributors to the magnetic shielding anisotropy is an occupied molecular orbital with significant vanadium d(z)2 character along the V=O bond.