Deciphering the NMR fingerprints of the disordered system with quantum chemical studies.
Deciphering the NMR fingerprints of the disordered system with quantum chemical studies.
复制标题
通过量子化学研究破译无序系统的核磁共振指纹。
DOI：
10.1021/jp9001324
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Zhang,Yong
中科院分区：
文献类型：
--
作者：
Ling,Yan;Zhang,Yong
固态核磁共振技术的最新发展有助于获得具有结构无序的固体系统的高分辨率核磁共振谱。但在这些系统中观察到的化学位移不等价的结构起源尚未被揭示。我们报告了 N,N-双(二苯基膦)-N-((S)-α-甲基苄基)胺中固态 NMR 谱的量子化学研究，其中在 13.0 ppm 范围内解析了 8 个非等价 31 P NMR 化学位移。使用不同量子化学方法、计算算法、分子间效应和结构的结果表明，对于无序体系，几何优化与实验NMR化学位移最一致，其理论与实验相关性R2= 0.949和SD = 1.1 ppm，或者当使用每个分子的两个未分配的NMR位移的平均值时R2= 0.994和SD = 0.4 ppm。此外，这些计算表明，该系统中的实验化学位移不等价主要是由于无序环境导致磷原子周围不同几何形状的结果。实验 31 P NMR 化学位移与两个构象角和一个键长密切相关（R2= 0.981），每个构象角与磷原子周围的三个键合相互作用之一相关。这些结果将促进量子化学技术在无序固体结构表征和核磁共振性质阐明中的应用。
Recent developments in solid-state NMR techniques helped acquire high-resolution NMR spectra for solid systems with structural disorder. But the structural origin of the observed chemical shift nonequivalence in these systems has not been revealed. We report a quantum chemical investigation of the solid-state NMR spectrum inN,N-bis(diphenylphosphino)-N-((S)-α-methylbenzyl)amine, where eight nonequivalent31P NMR chemical shifts were resolved with a range of 13.0 ppm. Results from using different quantum chemical methods, computational algorithms, intermolecular effects, and structures indicate that for the disordered system, geometry optimization gives the best accord with experimental NMR chemical shifts, which has a theory-versus-experiment correlationR2= 0.949 and SD = 1.1 ppm, orR2= 0.994 and SD = 0.4 ppm when the average of two unassigned NMR shifts for each molecule is used. In addition, these calculations indicate that the experimental chemical shift nonequivalence in this system is mainly a consequence of the different geometries around the phosphorus atoms due to disordered environments. The experimental31P NMR chemical shifts are well correlated (R2= 0.981) with two conformation angles and one bond length, each associated with one of the three bonding interactions around the phosphorus atoms. These results will facilitate the use of quantum chemical techniques in structural characterization of disordered solids and elucidation of NMR properties.