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首页> 外文期刊>ACS Omega >Experimental and Computational Evidence for “Double Pancake Bonds”: The Role of Dispersion-Corrected DFT Methods in Strongly Dimerized 5-Aryl-1λ2,3λ2-dithia-2,4,6-triazines
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Experimental and Computational Evidence for “Double Pancake Bonds”: The Role of Dispersion-Corrected DFT Methods in Strongly Dimerized 5-Aryl-1λ2,3λ2-dithia-2,4,6-triazines

机译：“双薄煎饼键”的实验和计算证据：分散校正的DFT方法在强二聚5-芳基-1λ2,3λ2-二硫-2,4,6-三嗪中的作用

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Crystal structures are reported for bicyclic 3-CF3C6H4CN5S3 and monocyclic 3-CF3C6H4CN3S2, the latter of which is strongly dimerized in a cis-cofacial geometry [3-CF3C6H4CN3S2]2. The title compounds have previously been characterized in solution by NMR, displaying spectra that are consistent with the structure of [3-CF3C6H4CN3S2]2 in the crystal with anti-oriented CF3 substituents. The interannular binding was investigated using density functional theory (DFT) methods. However, the DFT-optimized geometry spreads the aryl rings too far apart (centroid–centroid distances of ≥4.353 ? versus experimental distance of 3.850 ?). Significant improvements are obtained with dispersion-corrected DFT functionals B3LYP-D3, B3LYP-D3BJ, M062X, and APFD using the 6-311+G(2d,p) basis set. However, all of these overbind the aryl rings with centroid–centroid distances of 3.612, 3.570, 3.526, and 3.511 ?, respectively. After selecting B3LYP-D3BJ/6-311+G(2d,p) as the best method, five alternative dimer geometries were tested, and all were found to be binding; however, anti cofacial-4 (matching the structure in the solid state) is the most stable. Computed energies of the remainder are as follows: +7.0 kJ mol–1 (syn-cofacial-5), +26.7 kJ mol–1 (anti-cofacial-64), +27.0 kJ mol–1 (syn-cofacial-150), +102.0 kJ mol–1 (S,S-antarafacial), and +103.7 kJ mol–1 (S,N-antarafacial), where the suffixes are torsional angles around the CN3S2 thiazyl ring centroids. The binding in the four most stable cofacial dimers may be described by “double pancake bonding”.
机译：据报道双环3-CF3C6H4CN5S3和单环3-CF3C6H4CN3S2的晶体结构，单环3-CF3C6H4CN5S3在顺-界面几何形状[3-CF3C6H4CN3S2] 2中强烈二聚。先前已通过NMR在溶液中表征了标题化合物，显示的光谱与具有反方向CF3取代基的晶体中的[3-CF3C6H4CN3S2] 2结构一致。使用密度泛函理论（DFT）方法研究环间结合。但是，经DFT优化的几何结构使芳基环之间的距离太远（质心-质心距离≥4.353?，而实验距离为3.850？）。使用6-311 + G（2d，p）基集，通过色散校正的DFT功能B3LYP-D3，B3LYP-D3BJ，M062X和APFD获得了显着改进。然而，所有这些都使芳环与质心间的距离分别为3.612、3.570、3.526和3.511？。选择B3LYP-D3BJ / 6-311 + G（2d，p）作为最佳方法后，测试了五种替代的二聚体几何结构，发现它们均具有结合力;但是，anti cofacial-4（与固态结构匹配）是最稳定的。其余部分的计算能量如下：+7.0 kJ mol-1（syn-cofacial-150），+ 26.7 kJ mol-1（anti-cofacial-64），+ 27.0 kJ mol-1（syn-cofacial-150） ，+ 102.0 kJ mol-1（S，S对角）和+103.7 kJ mol-1（S，N对角），其中后缀是围绕CN3S2噻唑基质心的扭转角。四个最稳定的界面二聚体中的结合可通过“双煎饼结合”来描述。

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