Azizi Abolfazl, Ebrahimi Ali
Department of Chemistry, Computational Quantum Chemistry Laboratory, University of Sistan and Baluchestan, P.O. Box 98135-674, Zahedan, Iran.
Department of Chemistry, Computational Quantum Chemistry Laboratory, University of Sistan and Baluchestan, P.O. Box 98135-674, Zahedan, Iran.
J Mol Graph Model. 2017 Oct;77:225-231. doi: 10.1016/j.jmgm.2017.08.024. Epub 2017 Sep 4.
The interaction between positively charged aromatic groups (π-π) is characterized by stacked pyridinium ion derivatives X-PyH||X-PyH (XH, NH2, OH, CN, F, Br and Cl) at the M06-2X/6-311++G(d,p) level of theory in the presence of three solvents. The results indicate the formation of π-π stacking in a dielectric solvent can be due to the significant stability of the charge-charge repulsion forces. The trend in the absolute value of stacking interaction energy |ΔE⋯| with respect to the solvent is formamide>water>acetone. In all complexes, the π-π stacking interactions increase with the electron-donating substituents (EDSs) and decrease with the electron-withdrawing substituents (EWSs). Excellent correlations were found between the ΔE values of the complexes and a combination of Hammett substituent constants. The results obtained from the atoms in molecules (AIM) and natural bond orbital (NBO) analysis show that the sum of electron densities calculated at BCPs and CCPs between the rings (∑r and ∑ρ) and the sum of donor-acceptor interaction energies (∑E) from one ring to other can be used as useful descriptors in the prediction of ΔE⋯ values in the complexes.
在三种溶剂存在的情况下，在M06 - 2X/6 - 311++G(d,p)理论水平下，带正电荷的芳香基团之间的相互作用（π - π相互作用）以堆叠的吡啶鎓离子衍生物X - PyH||X - PyH（XH、NH₂、OH、CN、F、Br和Cl）为特征。结果表明，在介电溶剂中形成π - π堆积可能归因于电荷 - 电荷排斥力的显著稳定性。相对于溶剂，堆积相互作用能|ΔE⋯|绝对值的趋势为甲酰胺>水>丙酮。在所有配合物中，π - π堆积相互作用随供电子取代基（EDSs）增加而增强，随吸电子取代基（EWSs）增加而减弱。在配合物的ΔE值与哈米特取代基常数的组合之间发现了极好的相关性。从分子中的原子（AIM）和自然键轨道（NBO）分析获得的结果表明，在环之间的键临界点（BCPs）和环临界点（CCPs）处计算的电子密度总和（∑r和∑ρ）以及从一个环到另一个环的供体 - 受体相互作用能总和（∑E）可作为预测配合物中ΔE⋯值的有用描述符。
