One-bond 1 J (15 N─19 F) spin-spin coupling constants of cationic fluorinating reagents: Insights from DFT calculations,Magnetic Resonance in Chemistry

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One-bond 1 J (15 N─19 F) spin-spin coupling constants of cationic fluorinating reagents: Insights from DFT calculations
Magnetic Resonance in Chemistry ( IF 1.9 ) Pub Date : 2019-12-08 , DOI: 10.1002/mrc.4962
Giacomo Saielli _{1,

2}

Affiliation

We have investigated, by means of density functional theory protocols, the one‐bond 1J(15N─19F) spin–spin coupling constants in a series of fluorinating reagents, containing the N─F bond, recently studied experimentally. The results of the calculations show a very good linear relationship with the experimental values, even though only the M06‐2X(PCM)/pcJ‐2//B3LYP/6‐311G(d,p) level affords a very low mean absolute error. The calculations allow to analyze the various molecular orbitals contributions to the J coupling and to rationalize the observed positive sign, corresponding to a negative sign of the reduced spin–pin coupling constant K(N─F). Moreover, of the four Ramsey contributions, only the diamagnetic spin orbit is negligible, whereas the paramagnetic spin orbit and spin dipole terms decrease the magnitude of the Fermi contact (FC) term by an amount that goes from a minimum of 35% up to more than 60% of the FC term itself. Several effects have been investigated, namely, the contribution of the long‐range solvent reaction field, relativistic corrections, and conformational and vibrational effects.

中文翻译：

阳离子氟化试剂的单键 1 J (15 N─19 F) 自旋-自旋耦合常数：来自 DFT 计算的见解

我们通过密度泛函理论协议研究了最近通过实验研究的一系列氟化试剂中的单键 1J(15N─19F) 自旋耦合常数，其中包含 N─F 键。计算结果显示出与实验值非常好的线性关系，即使只有 M06-2X(PCM)/pcJ-2//B3LYP/6-311G(d,p) 水平提供了非常低的平均绝对误差. 计算允许分析各种分子轨道对 J 耦合的贡献，并使观察到的正号合理化，对应于减小的自旋-销耦合常数 K(N─F) 的负号。此外，在四个 Ramsey 贡献中，只有抗磁自旋轨道可以忽略不计，而顺磁自旋轨道和自旋偶极子项会降低费米接触 (FC) 项的大小，幅度从 FC 项本身的 35% 到 60% 以上。已经研究了几种效应，即长程溶剂反应场的贡献、相对论校正以及构象和振动效应。

更新日期：2019-12-08

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