Department of Chemistry, Shiraz University of Technology, Shiraz 71555-313, Iran.
Phys Chem Chem Phys. 2019 Jan 2;21(2):623-630. doi: 10.1039/c8cp07003b.
Quantum DFT calculations, corrected for long-range interactions, have been carried out on complex models formed between HF as a proton donor and 2-methylene-2H-indene derivatives as proton acceptors. Using various exocyclic X substitutions, mutual effects of the aromaticity and the strength of the resulting π-hydrogen bond (after its evaluation by AIM methodology) have been investigated. The results show that the aromaticity of 6-membered rings and the hydrogen bond strength increase upon increasing the electron-donating character of the X-substituents. Based on some aromaticity indices (HOMA, FLU, SA and NICS(1)zz), it has been shown that the formation of a π-hydrogen bond causes an increase of aromaticity of the 6-membered ring. Also, the strength of the resulting π-hydrogen bond (with an energy of about 4.0 to 7.0 kcal mol-1) depends on the aromaticity of the 6-membered ring and increases with an increase in the aromaticity. In addition, a linear relationship was found between the most negative value of the molecular electrostatic potential (Vmin) and the HOMA, which confirms that the Vmin in the region of the studied ring could be used as a new index to estimate the amount of aromaticity. The electronic properties of the complexes have also been evaluated by means of the molecular electrostatic potential (MEP), the atoms in molecules (AIM) and the natural bond orbital (NBO) analyses.
已对 HF 作为质子供体与 2-亚甲基-2H-茚衍生物作为质子受体之间形成的复杂模型进行了经过长程相互作用校正的量子 DFT 计算。通过各种外环 X 取代，研究了芳香性和所得 π-氢键（通过 AIM 方法评估）强度的相互影响。结果表明，随着 X 取代基供电子性质的增加，六元环的芳香性和氢键强度增加。基于一些芳香性指数（HOMA、FLU、SA 和 NICS(1)zz），表明形成 π-氢键会导致六元环芳香性增加。此外，所得 π-氢键的强度（能量约为 4.0 至 7.0 kcal mol-1）取决于六元环的芳香性，并随芳香性增加而增加。此外，在分子静电势（Vmin）的最负值和 HOMA 之间发现了线性关系，这证实了研究环区域的 Vmin 可以用作估计芳香性量的新指标。还通过分子静电势（MEP）、分子中的原子（AIM）和自然键轨道（NBO）分析评估了配合物的电子性质。
