Characterization of reactive intermediates by multinuclear diffusion-ordered NMR spectroscopy (DOSY).
Characterization of reactive intermediates by multinuclear diffusion-ordered NMR spectroscopy (DOSY).
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DOI：
10.1021/ar800127e
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发表时间：
2009-02-17
影响因子：
18.3
通讯作者：
Williard, Paul G.
中科院分区：
文献类型：
--
作者：
Li, Deyu;Keresztes, Ivan;Hopson, Russell;Williard, Paul G.
核磁共振（NMR）是测定分子结构的最强大和最广泛使用的技术。虽然传统的NMR数据分析涉及化学位移、耦合常数和NOE相互作用与特定结构特征的相关性，但40多年前引入的一种被严重忽视的方法，脉冲梯度自旋回波（PGSE），可以测量溶液中分子的扩散系数，从而提供它们的相对粒径。在20世纪90年代早期，PGSE序列被纳入一个二维实验，称为扩散有序NMR光谱（DOSY），其中一个维度代表化学位移数据，而第二维则通过扩散特性解析物种。这种组合提供了一个强有力的工具，用于识别多组分溶液中的单个物质，赢得了“NMR色谱法”的绰号。在这个帐户中，我们描述了我们的努力，利用DOSY技术来表征溶液中的有机金属反应中间体，以便将结构数据与通过X射线衍射确定的固态晶体结构相关联，并发现聚集体形成和溶剂化状态在反应机理中的作用。我们报道了我们在表征活性中间体如有机锂聚集体中使用DOSY技术的初步努力。从那时起，我们探索了各种超过1H的核的DOSY实验，包括6Li，7 Li，11B，13 C和29 Si。此外，我们提出了一个扩散系数-分子量关系，以确定分子量，聚集数和溶剂化状态的反应中间体。我们还引入了一个内部参考系统，以关联未知的活性中间体与已知的惰性分子标准，如芳香族化合物，末端烯烃，环烯烃，和四烷基硅烷的扩散性能。此外，我们利用DOSY解释的聚集数和溶剂化状态的有机金属中间体的反应性，动力学和有机反应机理的作用。通过在不同温度下利用多核DOSY方法，我们还将固态X射线结构与溶液中的结构相关联，并发现了新的反应性络合物，包括单体硼烯醇盐，产物抑制聚集体和烯丙基胺乙烯基锂化中的一系列中间体。正如我们的努力所强调的那样，DOSY技术提供了实用可行的NMR程序，并有望在扩展到三维实验时获得更强大的见解。
Nuclear magnetic resonance (NMR) is the most powerful and widely utilized technique for determining molecular structure. Although traditional NMR data analysis involves the correlation of chemical shift, coupling constant, and NOE interactions to specific structural features, a largely overlooked method introduced more than 40 years ago, pulsed gradient spin−echo (PGSE), measures diffusion coefficients of molecules in solution, thus providing their relative particle sizes. In the early 1990s, the PGSE sequence was incorporated into a two-dimensional experiment, dubbed diffusion-ordered NMR spectroscopy (DOSY), in which one dimension represents chemical shift data while the second dimension resolves species by their diffusion properties. This combination provides a powerful tool for identifying individual species in a multicomponent solution, earning the nickname “chromatography by NMR”. In this Account, we describe our efforts to utilize DOSY techniques to characterize organometallic reactive intermediates in solution in order to correlate structural data to solid-state crystal structures determined by X-ray diffraction and to discover the role of aggregate formation and solvation states in reaction mechanisms.In 2000, we reported our initial efforts to employ DOSY techniques in the characterization of reactive intermediates such as organolithium aggregates. Since then, we have explored DOSY experiments with various nuclei beyond1H, including6Li,7Li,11B,13C, and29Si. Additionally, we proposed a diffusion coefficient−formula weight relationship to determine formula weight, aggregation number, and solvation state of reactive intermediates. We also introduced an internal reference system to correlate the diffusion properties of unknown reactive intermediates with known inert molecular standards, such as aromatic compounds, terminal olefins, cycloolefins, and tetraalkylsilanes. Furthermore, we utilized DOSY to interpret the role of aggregation number and solvation state of organometallic intermediates in the reactivity, kinetics, and mechanism of organic reactions. By utilizing multinuclear DOSY methodologies at various temperatures, we also correlated solid-state X-ray structures with those in solution and discovered new reactive complexes, including a monomeric boron enolate, a product-inhibition aggregate, and a series of intermediates in the vinyl lithiation of allyl amines. As highlighted by our efforts, DOSY techniques provide practical and feasible NMR procedures and hold the promise of even more powerful insights when extended to three-dimensional experiments.
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影响因子：
2.8
作者：
HILMERSSON, G;DAVIDSSON, O
通讯作者：
DAVIDSSON, O
DOI：
10.1006/jmra.1996.0241
发表时间：
1996-12-01
期刊：
JOURNAL OF MAGNETIC RESONANCE SERIES A
影响因子：
--
作者：
Jerschow, A;Muller, N
通讯作者：
Muller, N
影响因子：
3.6
作者：
Li, Deyu;Sun, Chengzao;Williard, Paul G.
通讯作者：
Williard, Paul G.
影响因子：
5.2
作者：
Li, Deyu;Hopson, Russell;Williard, Paul G.
通讯作者：
Williard, Paul G.
影响因子：
0.6
作者：
Antalek, Brian
通讯作者：
Antalek, Brian