The Sodium Anion Is Strongly Perturbed in the Condensed Phase Even Though It Appears Like a Free Ion in Nuclear Magnetic Resonance Experiments
The Sodium Anion Is Strongly Perturbed in the Condensed Phase Even Though It Appears Like a Free Ion in Nuclear Magnetic Resonance Experiments
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DOI：
10.1021/acs.jpclett.9b03432
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发表时间：
2020-02-06
影响因子：
5.7
通讯作者：
Autschbach, Jochen
中科院分区：
文献类型：
--
作者：
Abella, Laura;Philips, Adam;Autschbach, Jochen
溶剂化钠阴离子（Na-）被认为基本上表现得像孤立的气相离子，与环境的相互作用很弱。例如，溶剂化的Na-的Na-23 NMR信号非常尖锐，尽管有强四极增宽的潜力。尖锐的NMR信号似乎表明离子的电子密度接近球形。在本研究中，从头算分子动力学模拟和四极弛豫速率计算进行了Na-/Na+ [2.2.2]穴状配体系统溶剂化甲胺，然后详细分析了在钠核的电场梯度。研究发现，Na-不像一个准自由离子，只与环境发生微弱的相互作用。相反，Na-填充的3s壳层与离子本身的核心和原子核的相互作用很弱，导致Na-在NMR实验中像自由离子一样出现。
Solvated sodium anions (Na-) were thought to behave essentially like isolated gas-phase ions that interact only weakly with their environments. For example, Na-23 NMR signals for solvated Na- are very sharp, despite the potential for strong quadrupolar broadening. The sharp NMR signals appear to indicate a nearly spherical electron density of the ion. For the present study, ab initio molecular dynamics simulations and quadrupolar relaxation rate calculations were carried out for the Na-/Na+ [2.2.2]cryptand system solvated in methylamine, followed by detailed analyses of the electric field gradient at the sodium nuclei. It is found that Na- does not behave like a quasi-free ion interacting only weakly with its environment. Rather, the filled 3s shell of Na- interacts weakly with the ion's own core and the nucleus, causing Na- to appear in NMR experiments like a free ion.