Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA.
Molecules. 2020 Feb 18;25(4):907. doi: 10.3390/molecules25040907.
The halogen-bond (X-bond) donors 1,3- and 1,4-diiodotetrafluorobenzene ( and , respectively) form cocrystals with -1,2-bis(2-pyridyl)ethylene () assembled by N···I X-bonds. In each cocrystal, 2()·2() and ()·(), the donor molecules support the C=C bonds of to undergo an intermolecular [2+2] photodimerization. UV irradiation of each cocrystal resulted in stereospecific and quantitative conversion of to -tetrakis(2-pyridyl)cyclobutane (). In each case, the reactivity occurs via face-to-face -stacked columns wherein nearest-neighbor pairs of molecules lie sandwiched between X-bond donor molecules. Nearest-neighbor C=C bonds are stacked criss-crossed in both cocrystals. The reactivity was ascribed to the olefins undergoing pedal-like motion in the solid state. The stereochemistry of is confirmed in cocrystals 2()·() and ()·().
卤键（X 键）供体 1,3- 和 1,4-二碘代四氟苯（和，分别）与 -1,2-双（2-吡啶基）乙烯（）形成 cocrystals，由 N···I X 键组装。在每个 cocrystal 中，2()·2() 和 ()·()，供体分子支撑 C=C 键的发生分子间 [2+2] 光二聚化。每个 cocrystal 的紫外辐射导致立体特异性和定量转化为 -四（2-吡啶基）环丁烷（）。在每种情况下，反应都是通过面对面 - 堆叠的柱发生的，其中最邻近的对分子位于 X 键供体分子之间。在两个 cocrystals 中，最近邻的 C=C 键交叉堆叠。反应归因于烯烃在固态中发生类似踏板的运动。在 cocrystals 2()·() 和 ()·() 中证实了的立体化学。
