51V solid-state NMR and density functional theory studies of vanadium environments in V(V)O2 dipicolinic acid complexes
51V solid-state NMR and density functional theory studies of vanadium environments in V(V)O2 dipicolinic acid complexes
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DOI：
10.1063/1.2830239
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发表时间：
2008-02-07
影响因子：
4.4
通讯作者：
Smee, Jason J.
中科院分区：
文献类型：
--
作者：
Bolte, Stephanie E.;Ooms, Kristopher J.;Smee, Jason J.
用V-51固体核磁共振和密度泛函理论研究了一系列五配位的二氧钒（V）-吡啶二甲酸盐[V（V）O-2-吡啶二甲酸盐]和七配位的羟胺氧钒（V）-吡啶二甲酸盐[V（V）O-吡啶二甲酸盐]配合物.这些化合物是令人感兴趣的，因为它们作为磷酸酶抑制剂的效力以及它们的胰岛素增强特性和治疗糖尿病的潜力。实验结果表明，V（V）O-2-吡啶二羧酸衍生物的电场梯度张量受吡啶二羧酸环上取代基的影响较大，其变化范围为5.8 ~ 8.3MHz.化学位移各向异性显示相对于配体变化的不太显著的变化，并且范围在-550至-600 ppm之间。为了深入了解NMR参数的起源，DFT计算进行了广泛系列的V（V）O-2-和V（V）O-吡啶二甲酸盐配合物。为了评估精确计算V-51 NMR参数所需的理论水平，在DFT研究中探索了不同的泛函、基组和结构模型。它示出，原始的X射线晶体学几何形状，包括所有抗衡离子和溶剂化水分子内的钒，导致最准确的结果。选择的功能和基础设置在一个高层次的理论有一个相对较小的影响的化学位移各向异性计算的结果，但是，使用大的基础设置是必要的精确计算的四极耦合常数的几个化合物的V（V）O-2系列。这些研究表明，尽管所研究的钒化合物具有扭曲的三角双锥配位几何结构，但它们具有“完美的”三角双锥电子环境。这一观察结果可能解释了为什么钒酸盐和钒（V）加合物通常被认为是有效的过渡态类似物。(c)2008年美国物理学会。
V-51 solid-state NMR and density functional theory (DFT) investigations are reported for a series of pentacoordinate dioxovanadium(V)-dipicolinate [V(V)O-2-dipicolinate] and heptacoordinate aquahydroxylamidooxovanadium(V)-dipicolinate [V(V)O-dipicolinate] complexes. These compounds are of interest because of their potency as phosphatase inhibitors as well as their insulin enhancing properties and potential for the treatment of diabetes. Experimental solid-state NMR results show that the electric field gradient tensors in the V(V)O-2-dipicolinate derivatives are affected significantly by substitution on the dipicolinate ring and range from 5.8 to 8.3 MHz. The chemical shift anisotropies show less dramatic variations with respect to the ligand changes and range between -550 and -600 ppm. To gain insights on the origins of the NMR parameters, DFT calculations were conducted for an extensive series of the V(V)O-2- and V(V)O-dipicolinate complexes. To assess the level of theory required for the accurate calculation of the V-51 NMR parameters, different functionals, basis sets, and structural models were explored in the DFT study. It is shown that the original x-ray crystallographic geometries, including all counterions and solvation water molecules within 5 A of the vanadium, lead to the most accurate results. The choice of the functional and the basis set at a high level of theory has a relatively minor impact on the outcome of the chemical shift anisotropy calculations; however, the use of large basis sets is necessary for accurate calculations of the quadrupole coupling constants for several compounds of the V(V)O-2 series. These studies demonstrate that even though the vanadium compounds under investigations exhibit distorted trigonal bipyramidal coordination geometry, they have a "perfect" trigonal bipyramidal electronic environment. This observation could potentially explain why vanadate and vanadium(V) adducts are often recognized as potent transition state analogs. (c) 2008 American Institute of Physics.