Ultra-wideline 27Al NMR investigation of three- and five-coordinate aluminum environments.
Ultra-wideline 27Al NMR investigation of three- and five-coordinate aluminum environments.
复制标题
三坐标和五坐标铝环境的超宽线 27Al NMR 研究。
作者：
Joel A Tang;Jason D. Masuda;T. Boyle;R. Schurko
超宽线27铝NMR实验进行了配合物与27铝核具有巨大的四极相互作用，导致异常非球形的配位环境。NMR光谱是使用涉及频率步进的方法获得的，使用Hahn-echo或四极Carr-Purcell Meiboom-Gill（QCPMG）脉冲序列分段采集NMR光谱，这适用于具有极宽NMR粉末图案的任何半整数四极核。尽管这些中央过渡粉末图案的大的宽度，从250到700 kHz，总的实验时间是一个数量级小于以前报道的类似的复合物与较小的四极相互作用的实验。所研究的络合物具有三或五配位铝位点：三均三甲苯基铝（AlMes 3）、三（双（三甲基甲硅烷基）氨基）铝（Al（NTMS 2）3）、双[二甲基四氢呋喃氧基铝]（[Me 2-Al（mu-OTHF）]2）和双[二乙基四氢呋喃氧基铝]（[Et 2-Al（mu-OTHF）]2）。我们报道了迄今为止测得的一些最大的27 Al四极耦合常数，AlMes 3，Al（NTMS 2）3，[Me 2-Al（mu-OTHF）]2和[Et 2-Al（mu-OTHF）] 2的C（Q）（27 Al）值分别为48.2（1），36.3（1），19.9（1）和19.6（2）MHz。利用X射线晶体学数据和27 Al电场梯度（EFG）张量的理论计算（Hartree-Fock和DFT）研究了四极相互作用与分子结构之间的关系，特别是通过分子轨道分析研究了三配位物种中巨大四极相互作用的起源.
Ultra-wideline 27Al NMR experiments are conducted on coordination compounds with 27Al nuclei possessing immense quadrupolar interactions that result from exceptionally nonspherical coordination environments. NMR spectra are acquired using a methodology involving frequency-stepped, piecewise acquisition of NMR spectra with Hahn-echo or quadrupolar Carr-Purcell Meiboom-Gill (QCPMG) pulse sequences, which is applicable to any half-integer quadrupolar nucleus with extremely broad NMR powder patterns. Despite the large breadth of these central transition powder patterns, ranging from 250 to 700 kHz, the total experimental times are an order of magnitude less than previously reported experiments on analogous complexes with smaller quadrupolar interactions. The complexes examined feature three- or five-coordinate aluminum sites: trismesitylaluminum (AlMes3), tris(bis(trimethylsilyl)amino)aluminum (Al(NTMS2)3), bis[dimethyl tetrahydrofurfuryloxide aluminum] ([Me2-Al(mu-OTHF)]2), and bis[diethyl tetrahydrofurfuryloxide aluminum] ([Et2-Al(mu-OTHF)]2). We report some of the largest 27Al quadrupolar coupling constants measured to date, with values of C(Q)(27Al) of 48.2(1), 36.3(1), 19.9(1), and 19.6(2) MHz for AlMes3, Al(NTMS2)3, [Me2-Al(mu-OTHF)]2, and [Et2-Al(mu-OTHF)]2, respectively. X-ray crystallographic data and theoretical (Hartree-Fock and DFT) calculations of 27Al electric field gradient (EFG) tensors are utilized to examine the relationships between the quadrupolar interactions and molecular structure; in particular, the origin of the immense quadrupolar interaction in the three-coordinate species is studied via analyses of molecular orbitals.
对碳酸酐酶的合成类似物进行固态 67Zn NMR 光谱研究和从头算分子轨道计算。
DOI：
10.1021/ja021328q
发表时间：
2003
期刊：
Journal of the American Chemical Society.
影响因子：
--
作者：
Lipton,AndrewS;Bergquist,Catherine;Parkin,Gerard;Ellis,PaulD
通讯作者：
Ellis,PaulD
影响因子：
15
作者：
Lipton, AS;Wright, TA;Ellis, PD
通讯作者：
Ellis, PD