Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India.
J Phys Chem B. 2011 Jun 2;115(21):6868-75. doi: 10.1021/jp112416q. Epub 2011 May 10.
We report the C-HETSERF experiment for determination of long- and short-range homo- and heteronuclear scalar couplings ((n)J(HH) and (n)J(XH), n ≥ 1) of organic molecules with a low sensitivity dilute heteronucleus in natural abundance. The method finds significant advantage in measurement of relative signs of long-range heteronuclear total couplings in chiral organic liquid crystal. The advantage of the method is demonstrated for the measurement of residual dipolar couplings (RDCs) in enantiomers oriented in the chiral liquid crystal with a focus to unambiguously assign R/S designation in a 2D spectrum. The alignment tensor calculated from the experimental RDCs and with the computed structures of enantiomers obtained by DFT calculations provides the size of the back-calculated RDCs. Smaller root-mean-square deviations (rmsd) between experimental and calculated RDCs indicate better agreement with the input structure and its correct designation of the stereogenic center.
我们报告了 C-HETSERF 实验，用于确定具有天然丰度低灵敏度稀释杂核的有机分子的同核和异核远程和短程标量耦合（(n)J(HH)和 (n)J(XH)，n ≥ 1）。该方法在测量手性有机液晶中长程异核总耦合的相对符号方面具有显著优势。该方法的优势通过测量在手性液晶中取向的对映异构体的残余偶极耦合（RDC）来证明，重点是在二维光谱中明确指定 R/S 命名。从实验 RDC 计算得到的并与通过 DFT 计算获得的对映异构体的计算结构相吻合的计算得到的排列张量提供了反算 RDC 的大小。实验和计算 RDC 之间的均方根偏差（rmsd）越小，与输入结构及其立体中心的正确指定的一致性越好。
