Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, 841051, Israel.
Chemistry. 2018 Nov 2;24(61):16348-16355. doi: 10.1002/chem.201802782. Epub 2018 Oct 4.
In a recent study, Scheiner designed a double-germanium-based fluoride receptor that binds the halogen by means of strong tetrel bonds (Chem. Eur. J. 2016, 22, 18850). In this system the F binds to the germanium atoms in an asymmetric fashion, thereby producing a double-well potential in which the fluoride can jump from one germanium to the other as in a ping-pong game. Herein we prove through the use of computational tools that at cryogenic temperatures this rearrangement occurs by heavy-atom quantum mechanical tunneling. The inductive strength of the substituents and the polarity of the solvent can modify the barrier and the tunneling rate. But the strongest effect is observed upon modification of the geometry of the molecule by specific substitutions that affect the barrier width, the most critical factor in a tunneling mechanism. We postulate two experimental tests, one by microwave spectroscopy and one by cryogenic NMR spectroscopy, that can prove the predicted fluoride tunneling.
在最近的一项研究中，Scheiner 设计了一种基于双锗的氟化物受体，通过强四中心键（Chem. Eur. J. 2016, 22, 18850）与卤素结合。在该体系中，F 以不对称的方式与锗原子结合，从而产生双势阱，氟化物可以像打乒乓球一样从一个锗原子跳到另一个锗原子。在此，我们通过使用计算工具证明，在低温下，这种重原子量子力学隧穿会导致这种重排。取代基的诱导强度和溶剂的极性可以改变势垒和隧穿速率。但最显著的影响是通过特定取代来改变分子的几何形状，这会影响到隧穿机制中最关键的因素——势垒宽度。我们提出了两个实验测试，一个是微波光谱学测试，另一个是低温 NMR 光谱学测试，可以证明预测的氟化物隧穿。
