分子内π–π堆积的晶体工程：F顺序取代对构象柔性磺酰胺中分子几何形状的影响,Crystal Growth & Design

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分子内π–π堆积的晶体工程：F顺序取代对构象柔性磺酰胺中分子几何形状的影响
Crystal Growth & Design ( IF 3.2 ) Pub Date : 2019-08-29 , DOI: 10.1021/acs.cgd.9b00667
Samir R. Shaikh ₁ , Rupesh L. Gawade , Deepak Kumar , Amol Kotmale , Rajesh G. Gonnade ₁ , Tobias Stürzer ₂

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合成了一个包含10个包含两个芳香环的磺酰胺衍生物的小型文库，以研究F原子按时间顺序排列对分子内π堆积组件的影响。F原子的顺序定位是在一个直接连接到磺酰胺部分的芳环上进行的，而另一个芳环（苯基或吡啶）是通过乙基间隔基与磺酰胺部分连接的。提供乙基间隔基是为了获得所需的柔韧性，以便两个芳环都可以弯曲以获得顺式构象促进了缺电子和富电子芳环之间的π堆积。这个想法是研究构象柔性磺酰胺衍生物中氢键和π-堆叠合成子之间的相互作用。使用单晶X射线衍射技术研究了所有衍生物的固态构象。晶体结构分析表明，仅在具有苯取代基的三氟和五氟磺酰胺衍生物中实现了顺式构象，而在所有其他衍生物中，分子呈中间或反式构象。没有一个具有吡啶部分的磺酰胺分子显示出顺式构象。这可能是由于吡啶的N原子参与了氢键二聚合成子。使用2D NOESY和HOESY NMR实验在溶液状态下进行的分子构象研究也证实了具有苯取代基的五氟磺酰胺分子中的顺式构象。使用密度泛函理论（DFT）计算进行的构象分析证实了合成构象在中途和反方向上具有更高的稳定性。

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Crystal Engineering for Intramolecular π–π Stacking: Effect of Sequential Substitution of F on Molecular Geometry in Conformationally Flexible Sulfonamides

A small library of ten sulfonamide derivatives comprising two aromatic rings was synthesized to investigate the effect of chronological positioning of the F-atom on the intramolecular π-stacking assembly. The sequential positioning of F-atoms was carried out on one of the aromatic rings that is linked to the sulfonamide moiety directly while the other aromatic ring (phenyl or pyridine) is linked by an ethyl spacer with the sulfonamide moiety. The ethyl spacer is provided to achieve the required flexibility so that both aromatic rings can bend to acquire syn conformation facilitated π-stacking between electron-deficient and electron-rich aromatic rings. The idea was to study the interplay between hydrogen bonding and π-stacking synthons in the conformationally flexible sulfonamide derivatives. The solid-state conformation of all the derivatives was investigated using the single-crystal X-ray diffraction technique. Crystal structure analysis revealed that the syn conformation was achieved only in trifluoro and pentafluoro sulfonamide derivatives with benzene substitution while in all other derivatives the molecules take either midway or anti conformations. None of the sulfonamide molecules with a pyridine moiety showed syn conformation. It could be because of the involvement of the pyridine N-atom in the hydrogen bonding dimeric synthon. The molecular conformation study in solution state using 2D NOESY and HOESY NMR experiments also substantiated syn conformation in a pentafluoro sulfonamide molecule with benzene substitution. The conformational analysis carried out employing density functional theory (DFT) calculations confirmed higher stability for the syn conformation over midway and anti orientations.

更新日期：2019-08-30

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