Paschoal Diego F S, Dos Santos Hélio F
NQTCM: Núcleo de Química Teórica e Computacional de Macaé, Polo Ajuda, Universidade Federal do Rio de Janeiro, Campus UFRJ-Macaé, 27.971-525, Macaé, RJ, Brazil.
Phys Chem Chem Phys. 2021 Mar 28;23(12):7240-7246. doi: 10.1039/d0cp06555b. Epub 2021 Mar 22.
The XeF molecule exists as a monomer in the gas phase and as the (XeF) tetramer in solution. Herein we used distinct quantum mechanics methods to study the conformational equilibrium for the XeF monomer, which is represented mainly by O and C symmetric geometries, and for the (XeF) structure found in condensate phases. The NMR J(Xe-F) coupling constant is predicted using our own NMR-DKH basis set, designed for NMR properties. The C conformer of XeF was stable only with HF, CCSD, and hybrid DFT functionals with at least 28% exact HF exchange. Increasing the % of HF exchange improves the description of the geometry and the O→C equilibrium. The BMK, BHandHLYP and LC-ωPBE functionals produce results in excellent agreement with experiments and high-level calculations for the XeF molecule. When it comes to the J(Xe-F) coupling constant, the (XeF) structure must be considered. For that compound, BHandHLYP leads to the best structure, and BMK leads to the best coupling constant; therefore, the generalized protocol BMK/NMR-DKH//BHandHLYP/def2-SVP is recommended to study the XeF molecule in the gas phase and solution.
XeF分子在气相中以单体形式存在，在溶液中以(XeF)四聚体形式存在。在此，我们使用不同的量子力学方法研究XeF单体的构象平衡，其主要由O和C对称几何结构表示，以及在凝聚相中发现的(XeF)结构的构象平衡。使用我们专门为NMR性质设计的NMR-DKH基组预测NMR J(Xe-F)耦合常数。XeF的C构象异构体仅在使用HF、CCSD以及具有至少28%精确HF交换的杂化DFT泛函时才稳定。增加HF交换的百分比可改善对几何结构和O→C平衡的描述。BMK、BHandHLYP和LC-ωPBE泛函产生的结果与XeF分子的实验结果和高水平计算结果高度吻合。对于J(Xe-F)耦合常数，必须考虑(XeF)结构。对于该化合物，BHandHLYP给出最佳结构，BMK给出最佳耦合常数；因此，建议使用通用方案BMK/NMR-DKH//BHandHLYP/def2-SVP来研究气相和溶液中的XeF分子。
