Wilkens S J, Westler W M, Markley J L, Weinhold F
National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, 433 Babcock Drive, Madison, Wisconsin 53706, USA.
J Am Chem Soc. 2001 Dec 5;123(48):12026-36. doi: 10.1021/ja016284k.
The natural J-coupling (NJC) method presented here analyzes the Fermi contact portion of J-coupling in the framework of finite perturbation theory applied to ab initio/density function theory (DFT) wave functions, to compute individual and pairwise orbital contributions to the net J-coupling. The approach is based on the concepts and formalisms of natural bond orbital (NBO) methods. Computed coupling contributions can be classified as Lewis (individual orbital contributions corresponding to the natural Lewis structure of the molecule), delocalization (resulting from pairwise donor-acceptor interactions), and residual repolarization (corresponding to correlation-like interactions). This approach is illustrated by an analysis of the angular and distance dependences of the contributions to vicinal (3)J(HH) couplings in ethane and to the long-range (6)J(HH) couplings in pentane. The results indicate that approximately 70% or more of the net J-coupling is propagated by steric exchange antisymmetry interactions between Lewis orbitals (predominantly sigma bonding orbitals). Hyperconjugative sigma to sigma delocalization interactions account for the remainder of the coupling. Calculated pairwise-steric and hyperconjugative-delocalization energies provide a means for relating coupling mechanisms to molecular energetics. In this way, J-coupling contributions can be related directly to the localized features of the molecular electronic structure in order to explain measured J-coupling patterns and to predict J-coupling trends that have yet to be measured.
本文提出的自然 J 耦合（NJC）方法，在应用于从头算/密度泛函理论（DFT）波函数的有限微扰理论框架内，分析 J 耦合的费米接触部分，以计算对净 J 耦合的单个和成对轨道贡献。该方法基于自然键轨道（NBO）方法的概念和形式体系。计算得到的耦合贡献可分为路易斯型（与分子的自然路易斯结构相对应的单个轨道贡献）、离域型（由成对的供体-受体相互作用产生）和残余再极化型（对应于类似相关的相互作用）。通过分析乙烷中邻位（3）J（HH）耦合贡献以及戊烷中远程（6）J（HH）耦合贡献的角度和距离依赖性，对该方法进行了说明。结果表明，净 J 耦合的大约 70%或更多是通过路易斯轨道（主要是σ键轨道）之间的空间交换反对称相互作用传播的。超共轭σ到σ离域相互作用占耦合的其余部分。计算得到的成对空间和超共轭离域能量为将耦合机制与分子能量学联系起来提供了一种手段。通过这种方式，J 耦合贡献可以直接与分子电子结构的局部特征相关联，以便解释测得的 J 耦合模式并预测尚未测量的 J 耦合趋势。
