Chemistry Institute, State University of Campinas, Caixa Postal 6154, 13084-971 Campinas, SP, Brazil.
J Phys Chem A. 2011 Feb 24;115(7):1272-9. doi: 10.1021/jp110290b. Epub 2011 Jan 31.
Interesting insight into the electronic molecular structure changes associated with substituent effects on the Fermi contact (FC) and paramagnetic spin-orbit (PSO) terms of (1)J(CF) NMR coupling constants (SSCCs) in o-X-, m-X-, and p-X-fluorobenzenes (X = NH(2); NO(2)) is presented. The formulation of this approach is based on the influence of different conjugative and hyperconjugative interactions on a second-order property, which can be qualitatively predicted if it is known how they affect the main virtual excitations entering into that second-order property. A set of consistent approximations are introduced in order to analyze the behavior of occupied and virtual orbitals, which define some experimental trends for (1)J(CF) spin-spin coupling constants. In addition, DFT hybrid functionals were used, and a similar degree of confidence to compute the (1)J(CF) with those observed for the SOPPA(CCSD) method was obtained. The (1)J(CF) SSCCs for ezetimibe, a commercially fluorinated drug used to reduce cholesterol levels, were measured and DFT-calculated, and the qualitative approach quoted above was applied. As a byproduct, a possible method to determine experimentally a significant PSO contribution to (1)J(CF) SSCCs is discussed.
本文对取代效应对邻位、间位和对位氟苯（X = NH2；NO2）中（1）J（CF）NMR 偶合常数（SSCCs）的费米接触（FC）和顺磁自旋-轨道（PSO）项的电子分子结构变化进行了有趣的研究。该方法的公式基于不同共轭和超共轭相互作用对二阶性质的影响，如果知道它们如何影响进入该二阶性质的主要虚拟激发，就可以定性预测。为了分析占据轨道和空轨道的行为，引入了一组一致的近似，这些近似可以解释（1）J（CF）自旋-自旋偶合常数的一些实验趋势。此外，还使用了 DFT 杂化泛函，并且对于计算（1）J（CF）的置信度与 SOPPA（CCSD）方法观察到的置信度相似。测定了一种用于降低胆固醇水平的商业氟化药物依泽替米贝的（1）J（CF）SSCC，并进行了 DFT 计算，应用了上述定性方法。作为副产品，讨论了一种可能的实验方法来确定（1）J（CF）SSCC 中 PSO 项的显著贡献。
