The cocrystal formed by hexamethylbenzene (HMB) with 1,3-diiodotetrafluorobenzene (1,3-DITFB) was first synthesized and found to have an unexpected sandwiched-layer structure with alternating HMB layers and 1,3-DITFB layers. To better understand the formation of this special structure, all the noncovalent interactions between these molecules in the gas phase and the cocrystal structure have been investigated in detail by using the dispersion-corrected density functional theory calculations. In the cocrystal structure, the theoretically predicted π···π stacking interactions between HMB and the 1,3-DITFB molecules in the gas phase can be clearly seen, whereas there are no π···π stacking interactions between HMB molecules or between 1,3-DITFB molecules. The attractive interactions between HMB molecules in the corrugated HMB layers originate mainly in the dispersion forces. The 1,3-DITFB molecules form a 2D sheet structure via relatively weak C–I···F halogen bonds. The theoretically predicted much stronger C–I···π halogen bonds between HMB and 1,3-DITFB molecules in the gas phase are not found in the cocrystal structure. We concluded that it is the special geometry of 1,3-DITFB that leads to the formation of the sandwiched-layer structure of the cocrystal.

中文翻译：

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六甲基苯与1,3-二碘四氟苯形成共晶的意外夹层结构：理论和晶体学联合研究

首先合成了由六甲基苯（HMB）与1,3-二碘四氟苯（1,3-DITFB）形成的共晶体，发现该晶体具有意想不到的夹层结构，具有交替的HMB层和1,3-DITFB层。为了更好地理解这种特殊结构的形成，通过使用色散校正的密度泛函理论计算，对这些分子在气相和共晶结构之间的所有非共价相互作用进行了详细研究。在共晶结构中，可以清楚地看到HMB与气相中1,3-DITFB分子之间理论上预测的π··π堆积相互作用，而HMB分子之间或HMB分子之间没有π···π堆积相互作用。 1,3-DITFB分子。瓦楞纸HMB层中的HMB分子之间的吸引力相互作用主要源自分散力。1,3-DITFB分子通过相对弱的C-1·F卤素键形成2D薄片结构。从理论上预测，在共晶结构中未发现气相中HMB和1,3-DITFB分子之间更强的C–I··π卤素键。我们得出结论，正是1,3-DITFB的特殊几何形状导致了共晶夹层结构的形成。