Supramolecular Sandwiches: Halogen-Bonded Coformers Direct [2+2] Photoreactivity in Two-Component Cocrystals
Supramolecular Sandwiches: Halogen-Bonded Coformers Direct [2+2] Photoreactivity in Two-Component Cocrystals
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DOI：
10.3390/molecules25040907
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发表时间：
2020-02-02
期刊：
影响因子：
4.6
通讯作者：
MacGillivray, Leonard R.
中科院分区：
文献类型：
--
作者：
Quentin, Jay;Swenson, Dale C.;MacGillivray, Leonard R.
卤素键（X键）供体1,3-和1,4-二碘四氟苯（分别为1,3-二-I-tFb和1,4-二-I-tFb）与反式1,2-双（2-吡啶基）乙烯（2,2'-bpe）通过N中心点X键组装形成共晶。在每个共晶中，2(1,3-di-I-tFb)中心点2(2,2'-bpe)和(1,4-di-I-tFb)中心点(2,2'-bpe)，供体分子支持2,2'-bpe的C=C键以进行分子间[2+2]光二聚化。每个共晶的紫外线照射导致 2,2'-bpe 立体定向和定量转化为 rctt-四(2-吡啶基)环丁烷 (2,2'-tpcb)。在每种情况下，反应都是通过面对面的π堆积柱发生，其中最近邻的2,2'-bpe分子对夹在X键供体分子之间。最近邻的 C=C 键在两个共晶中交叉堆叠。这种反应性归因于烯烃在固态下经历类似踏板的运动。 2,2'-tpcb 的立体化学在共晶 2(1,3-di-I-tFb)center dot(2,2'-tpcb) 和 (1,4-di-I-tFb)center dot(2,2'-tpcb) 中得到证实。
The halogen-bond (X-bond) donors 1,3- and 1,4-diiodotetrafluorobenzene (1,3-di-I-tFb and 1,4-di-I-tFb, respectively) form cocrystals with trans-1,2-bis(2-pyridyl)ethylene (2,2'-bpe) assembled by N center dot center dot center dot I X-bonds. In each cocrystal, 2(1,3-di-I-tFb)center dot 2(2,2'-bpe) and (1,4-di-I-tFb)center dot(2,2'-bpe), the donor molecules support the C=C bonds of 2,2'-bpe to undergo an intermolecular [2+2] photodimerization. UV irradiation of each cocrystal resulted in stereospecific and quantitative conversion of 2,2'-bpe to rctt-tetrakis(2-pyridyl)cyclobutane (2,2'-tpcb). In each case, the reactivity occurs via face-to-face pi-stacked columns wherein nearest-neighbor pairs of 2,2'-bpe 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 2,2'-tpcb is confirmed in cocrystals 2(1,3-di-I-tFb)center dot(2,2'-tpcb) and (1,4-di-I-tFb)center dot(2,2'-tpcb).