Computational Chemistry Laboratory, Chemistry Department, Faculty of Science, Minia University, Minia 61519, Egypt.
Department of Chemistry, The University of Azad Jammu and Kashmir, Muzaffarabad 13100, Pakistan.
Int J Mol Sci. 2022 Mar 14;23(6):3114. doi: 10.3390/ijms23063114.
In the current study, unexplored type IV halogen⋯halogen interaction was thoroughly elucidated, for the first time, and compared to the well-established types I−III interactions by means of the second-order Møller−Plesset (MP2) method. For this aim, the halobenzene⋯halobenzene homodimers (where halogen = Cl, Br, and I) were designed into four different types, parodying the considered interactions. From the energetic perspective, the preference of scouted homodimers was ascribed to type II interactions (i.e., highest binding energy), whereas the lowest binding energies were discerned in type III interactions. Generally, binding energies of the studied interactions were observed to decline with the decrease in the σ-hole size in the order, C6H5I⋯IC6H5 > C6H5Br⋯BrC6H5 > C6H5Cl⋯ClC6H5 homodimers and the reverse was noticed in the case of type IV interactions. Such peculiar observations were relevant to the ample contributions of negative-belt⋯negative-belt interactions within the C6H5Cl⋯ClC6H5 homodimer. Further, type IV torsional trans → cis interconversion of C6H5X⋯XC6H5 homodimers was investigated to quantify the π⋯π contributions into the total binding energies. Evidently, the energetic features illustrated the amelioration of the considered homodimers (i.e., more negative binding energy) along the prolonged scope of torsional trans → cis interconversion. In turn, these findings outlined the efficiency of the cis configuration over the trans analog. Generally, symmetry-adapted perturbation theory-based energy decomposition analysis (SAPT-EDA) demonstrated the predominance of all the scouted homodimers by the dispersion forces. The obtained results would be beneficial for the omnipresent studies relevant to the applications of halogen bonds in the fields of materials science and crystal engineering.
在当前的研究中，首次彻底阐明了未探索的 IV 型卤⋯卤相互作用，并通过二阶 Møller−Plesset (MP2) 方法与已建立的 I−III 型相互作用进行了比较。为此，设计了四种不同类型的卤苯⋯卤苯同二聚体（其中卤素 = Cl、Br 和 I），模仿了所考虑的相互作用。从能量角度来看，所探索的同二聚体的偏好归因于 II 型相互作用（即最高结合能），而 III 型相互作用的结合能最低。一般来说，研究相互作用的结合能随着 σ-hole 尺寸的减小而降低，顺序为 C6H5I⋯IC6H5 > C6H5Br⋯BrC6H5 > C6H5Cl⋯ClC6H5 同二聚体，而在 IV 型相互作用中则相反。这种特殊的观察结果与 C6H5Cl⋯ClC6H5 同二聚体中负带⋯负带相互作用的大量贡献有关。此外，还研究了 C6H5X⋯XC6H5 同二聚体的 IV 型扭转反 → 顺互变异构，以量化 π⋯π 对总结合能的贡献。显然，能量特征说明了所考虑的同二聚体的改善（即更负的结合能）随着扭转反 → 顺互变异构的范围延长。反过来，这些发现概述了顺式构型相对于反式类似物的效率。一般来说，基于对称适应微扰理论的能量分解分析（SAPT-EDA）表明，所有探索的同二聚体都由色散力主导。获得的结果将有助于广泛的研究，这些研究与卤键在材料科学和晶体工程领域的应用有关。
