Measurement of aluminum-carbon distances using S-RESPDOR NMR experiments.
Measurement of aluminum-carbon distances using S-RESPDOR NMR experiments.
复制标题
DOI：
10.1002/cphc.201200490
复制
发表时间：
2012-11
期刊：
影响因子：
--
通讯作者：
F. Pourpoint;J. Trébosc;R. Gauvin;Qiang Wang;O. Lafon;F. Deng;J. Amoureux
中科院分区：
文献类型：
--
作者：
F. Pourpoint;J. Trébosc;R. Gauvin;Qiang Wang;O. Lafon;F. Deng;J. Amoureux
它表明，可靠的铝-碳距离可以测量样品中的（13）C天然丰度的NMR光谱。过耦合谐振器，只有一个射频合成器和一个放大器，被用来照射在相同的脉冲序列（27）铝和（13）C核，这在拉莫尔频率只有3.6%的差异。（27）Al饱和脉冲与异质偶极再耦合的组合产生（13）C信号的偶极移相，其仅取决于Al-C距离和饱和脉冲的效率。因此，可靠的距离，可以通过快速拟合的实验数据的分析表达式。它表明，与天然同位素丰度，这种方法允许回收的铝-C距离为216 μ m的共价键在四烷基铝酸锂，通常用作烯烃聚合过程中的助催化剂，和范围从274到381 μ m的三个碳原子在乳酸铝。核间距测量的准确性进行了仔细的估计。
It is demonstrated that reliable aluminum-carbon distances can be measured in samples with (13)C natural abundance by NMR spectroscopy. Overcoupled resonators, with only one radio-frequency synthesizer and one amplifier, are used to irradiate in the same pulse sequence (27)Al and (13)C nuclei, which differ by only 3.6 % in Larmor frequencies. The combination of (27)Al saturation pulse with heteronuclear dipolar recoupling yields dipolar dephasing of the (13)C signal, which only depends on the Al-C distance and the efficiency of the saturation pulse. Therefore, reliable distances can be obtained by rapid fitting of experimental data to an analytical expression. It is demonstrated that with natural isotopic abundance this approach allows recovery of Al-C distances of 216 pm for the covalent bond in lithium tetraalkyl aluminates, commonly used as a co-catalyst in olefin polymerization processes, and which range from 274 to 381 pm for the three carbon atoms in aluminum lactate. The accuracy of the measured internuclear distances is carefully estimated.