Strategies for the Hyperpolarization of Acetonitrile and Related Ligands by SABRE
Strategies for the Hyperpolarization of Acetonitrile and Related Ligands by SABRE
复制标题
DOI：
10.1021/jp511492q
复制
发表时间：
2015-01-29
影响因子：
3.3
通讯作者：
Williamson, David C.
中科院分区：
文献类型：
--
作者：
Mewis, Ryan E.;Green, Richard A.;Williamson, David C.
我们报告的战略，使用SABRE（信号放大可逆交换）极化H-1和C-13核的弱相互作用的林根，具有生物相关的和非芳香基序。我们首先使用Ir（IMes）（COD）Cl作为催化剂前体通过乙腈的极化证明了这一点，并确认超极化转移的途径是通过J -耦合网络。我们将这项工作扩展到丙腈，苄腈，苯甲腈，和反式-3-己烯二腈的极化，以评估其一般性。在H-1 NMR谱中，当[Ir（H）（2）（IMes）（MeCN）（3）]（+）为催化剂时，乙腈的信号比其热对应物增强8倍。加入吡啶或吡啶-d（5）后，活性催化剂变为[Ir（H）（2）（IMes）（py）（2）（MeCN）]（+），所得乙腈H-1信号增强分别增加至20倍和60倍。在C-13 NMR研究中，极化最佳地转移到MeCN的四元C-13核，而甲基C-13几乎不极化。转移到C-13的反应首先通过C-13和甲基质子之间的H-1-H-1偶联进行，然后通过（2）J或（1）J偶联到相应的Cs-13上，其中（2）J途径更有效。这些实验结果是合理的，通过理论处理，表现出良好的协议与实验。在MeCN的情况下，在三自旋甲基中的H-1核对之间产生纵向双自旋顺序。还产生了H-I和C-13核之间的双自旋有序态，并且使用Only Parahydrogen Spectroscopy方案在H-I和C-13 NMR谱中证实了（MeCN）-C-13的双自旋有序态的存在。
We report on a strategy for using SABRE (signal amplification by reversible exchange) for polarizing H-1 and C-13 nuclei of weakly interacting lingans which possess biologically relevant and nonaromatic motifs. We first demonstrate this via the polarization of acetonitrile, using Ir(IMes) (COD) CI as the catalyst precursor, and confirm that the route to hyperpolarization transfer is via the J - coupling network. We extend this work to the polarization of propionitrile, benzylnitrile, benzonitirle, and trans-3-hexenedinitrile in order to assess its generality. In the H-1 NMR spectrum, the signal for acetonitrile is enhanced 8-fold over its thermal counterpart when [Ir(H)(2) (IMes) (MeCN)(3)](+) is the catalyst. Upon addition of pyridine or pyridine-d(5), the active catalyst changes to [Ir(H)(2) (IMes) (py)(2) (MeCN)](+) and the resulting acetonitirle H-1 signal enhancement increases to 20- and 60-fold, respectively. In C-13 NMR studies, polarization transfers to optimally to the quaternary C-13 nucleus of MeCN while the methyl C-13 is hardly polarzied. Transfer to C-13 is shown to occur first via the H-1-H-1 coupling betwen the hydrides and the methyl protons and then via either the (2)J or (1)J couplings to the resepctive Cs-13, of which the (2)J route is more efficient. These experimental results are rationalized through a theoretical treatment which shows excellent agreement with experiment. In the case of MeCN, longitudinal two-spin orders between pairs of H-1 nuclei in the three-spin methylgroup are created. Two-spin order states, between the H-1 and C-13 nuclei, are also created, and their existence is confirmed for (MeCN)-C-13 in both the H-1 and C-13 NMR spectra using the Only Parahydrogen Spectroscopy protocol.