Foroutan-Nejad Cina, Badri Zahra, Marek Radek
CEITEC - Central European Institute of Technology, Masaryk University, Kamenice 5/A4, CZ-625 00 Brno, Czech Republic.
Phys Chem Chem Phys. 2015 Nov 11;17(45):30670-9. doi: 10.1039/c5cp05777a.
Exploring the nature of anion-π bonding by means of the Quantum Theory of Atoms in Molecules (QTAIM) and an energy decomposition scheme on the basis of Interacting Quantum Atoms (IQA) theory led us to conclude that these non-classical interactions benefit from "multi-center covalency" far more than from the electrostatics. Comparing anion-π systems to closely related covalent anion-σ complexes reveals that the anion-π systems benefit from an extensive degree of electron sharing between the anions and all atoms of the π-rings. Besides, decomposition of the binding energy into classical (electrostatics) and non-classical (exchange-correlation) components demonstrates that in contrast to previous reports, the anion-π complexes are local minima, if and only if the non-classical contribution to binding energy surpasses that of the electrostatics. This suggests that the stable anion-π complexes with the anions atop the π-rings might be prepared with π-systems that benefit more from the exchange-correlation term, such as extended π-systems, but not with strong electrostatic π-receptors. This conclusion is in line with the tendency of strong π-acids to form the σ-complexes with more covalent character instead of the π-complexes.
借助分子中原子的量子理论（QTAIM）以及基于相互作用量子原子（IQA）理论的能量分解方案，对阴离子 - π键的本质进行探索后，我们得出结论：这些非经典相互作用更多地受益于“多中心共价性”，而非静电作用。将阴离子 - π体系与密切相关的共价阴离子 - σ配合物进行比较发现，阴离子 - π体系受益于阴离子与π环所有原子之间广泛程度的电子共享。此外，将结合能分解为经典（静电）和非经典（交换 - 相关）成分表明，与之前的报道相反，阴离子 - π配合物是局部极小值，当且仅当对结合能的非经典贡献超过静电贡献时。这表明，对于π环上方带有阴离子的稳定阴离子 - π配合物，可以用从交换 - 相关项中受益更多的π体系来制备，比如扩展π体系，但不能用强静电π受体来制备。这一结论与强π酸倾向于形成具有更多共价特征的σ配合物而非π配合物的趋势一致。
