Shalit Yaffa, Tuvi-Arad Inbal
Department of Natural Sciences, The Open University of Israel, Raanana 4353701, Israel.
ACS Omega. 2021 Jul 16;6(29):19233-19237. doi: 10.1021/acsomega.1c02684. eCollection 2021 Jul 27.
The gas-phase structure of 18-crown-6 in the presence of Li and Na cations is highly flexible and generally distorted. Using density functional theory calculations, natural bond orbital analysis, and symmetry measures, we reveal the driving forces behind the structural and energy trends of 18-crown-6 and its phenyl substituents. We show that the structural deviation from -symmetry increases with the non-bonded interactions between the occupied sp orbitals of the crowns' oxygen atoms and the unoccupied 2s orbital of the cation. These orbital interactions are strongly correlated with the overall host-guest interaction energy. Our approach highlights the role of non-bonded interactions and paves the way for deeper understanding of structure-reactivity relations of flexible host-guest systems.
在锂和钠阳离子存在下，18-冠-6的气相结构具有高度灵活性且通常会发生扭曲。通过密度泛函理论计算、自然键轨道分析和对称性测量，我们揭示了18-冠-6及其苯基取代基的结构和能量趋势背后的驱动力。我们表明，与皇冠型氧原子占据的sp轨道和阳离子未占据的2s轨道之间的非键相互作用会导致结构偏离对称性增加。这些轨道相互作用与整体主客体相互作用能密切相关。我们的方法突出了非键相互作用的作用，并为深入理解柔性主客体系统的结构-反应性关系铺平了道路。
