Department of Chemistry University at Buffalo State University of New York Buffalo, NY 14260-3000, USA.
Phys Chem Chem Phys. 2021 Jan 6;23(1):339-346. doi: 10.1039/d0cp06012g.
The sodium anion (Na-) was once thought to behave like a 'genuine' anion, with both the [Ne] core and the 3s valence shell interacting very weakly with their environments. In the present work, following a recent study of the surprisingly small quadrupolar line widths of Na-, NMR shielding calculations were carried out for the Na-/Na+ [2.2.2]cryptand system solvated in methylamine, based on ab initio molecular dynamics simulations, followed by detailed analyses of the shielding constants. The results confirm that Na- does not act like a quasi-free ion that interacts only weakly with its surroundings. Rather, the filled 3s shell of Na- interacts strongly with its chemical environment, but only weakly with the ion's own core and the nucleus, and it isolates the core from the chemical environment. As a consequence, the Na- ion appears in NMR experiments like a free ion.
钠离子 (Na-) 曾被认为具有“真正”阴离子的行为，[Ne] 核和 3s 价壳层与它们的环境相互作用非常弱。在本工作中，继最近对 Na- 的令人惊讶的小四极线宽的研究之后，根据从头算分子动力学模拟，对甲基胺溶剂化的 Na-/Na+ [2.2.2]穴醚体系进行了 NMR 屏蔽计算，随后对屏蔽常数进行了详细分析。结果证实，Na- 不像仅与周围环境弱相互作用的准自由离子那样。相反，Na-的填满的 3s 壳层与化学环境强烈相互作用，但与离子自身的核和核仅弱相互作用，并将核与化学环境隔离。因此，在 NMR 实验中，Na- 离子表现得像自由离子。
