Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London W12 0BZ, U.K.
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, U.K.
J Am Chem Soc. 2021 Mar 17;143(10):3934-3943. doi: 10.1021/jacs.1c00115. Epub 2021 Mar 4.
The nature of anionic alkali metals in solution is traditionally thought to be "gaslike" and unperturbed. In contrast to this noninteracting picture, we present experimental and computational data herein that support ion pairing in alkalide solutions. Concentration dependent ionic conductivity, dielectric spectroscopy, and neutron scattering results are consistent with the presence of superalkali-alkalide ion pairs in solution, whose stability and properties have been further investigated by DFT calculations. Our temperature dependent alkali metal NMR measurements reveal that the dynamics of the alkalide species is both reversible and thermally activated suggesting a complicated exchange process for the ion paired species. The results of this study go beyond a picture of alkalides being a "gaslike" anion in solution and highlight the significance of the interaction of the alkalide with its complex countercation (superalkali).
传统上认为，溶液中阴离子碱金属的性质是“气态”的，且不受干扰。与这种非相互作用的图像形成对比的是，我们在此展示了实验和计算数据，这些数据支持碱金属溶液中的离子配对。浓度依赖性离子电导率、介电光谱和中子散射结果与溶液中超碱-碱金属离子对的存在一致，其稳定性和性质已通过 DFT 计算进一步研究。我们的温度依赖的碱金属 NMR 测量表明，碱金属物种的动力学是可逆和热激活的，这表明离子对物种的交换过程很复杂。这项研究的结果超出了碱金属在溶液中是“气态”阴离子的图像，并强调了碱金属与其复杂的反离子（超碱）相互作用的重要性。
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