Metastable Polymorphic Form of Isopropylbenzophenone Derivative Directly Obtained by the Solid-state Photoreaction Investigated by ab initio Powder X-ray Diffraction Analysis
Metastable Polymorphic Form of Isopropylbenzophenone Derivative Directly Obtained by the Solid-state Photoreaction Investigated by ab initio Powder X-ray Diffraction Analysis
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通过从头算粉末 X 射线衍射分析研究固态光反应直接获得异丙基二苯甲酮衍生物的亚稳态多晶型
DOI：
10.1039/c0ce00500b
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发表时间：
2011
期刊：
影响因子：
3.1
通讯作者：
Kotaro Fujii
中科院分区：
文献类型：
--
作者：
Hideko Koshima;Kyoko Takechi;Hidetaka Uchimoto;Motoo Shiro;Daisuke Hashizume;Kotaro Fujii
已知2-(2，4，6-triisopropybenzoyl)((S)-1-phenylethyl)benzamide(1)的晶态在紫外光照射下经历了非对映特定的Norrish II型光环化反应，得到单一的光产物(R，S)-环丁烯醇(2)。它的多晶型(2A)具有不同于已知多晶型2B的X射线衍射图，该多晶型2B是通过光产物的再结晶获得的。这种由固态光反应引起的多态现象本身是非常有趣的，光产物2A的结构应该直接导致光反应机理。由此，直接从粉末X射线衍射数据确定了该化合物的晶体结构。有趣的是，在光反应过程中，晶体堆积被保留了下来，尽管粉末X射线衍射图有很大的不同，但只有微小的结构变化。比较了1和A的晶体结构，揭示了光反应机理。多晶型的晶格能计算表明，仅通过固相光反应获得的晶格能比2B的稳定性差，这就是为什么它不会在再结晶时再结晶。
The crystalline state of 2-(2,4,6-triisopropybenzoyl)((S)-1-phenylethyl)benzamide (1) is known to undergo a diastereospecific Norrish type II photocyclization under UV irradiation, giving a single photoproduct (R,S)-cyclobutenol (2). Its polycrystalline form (2A) has a different X-ray diffraction pattern from the known polymorph 2B, which is obtained from recrystallization of the photoproduct. Such a polymorphic phenomenon, which is the result of a solid-state photoreaction, is, in itself, highly interesting and the structure of the photoproduct 2A should directly lead to the photoreaction mechanism. Thus, the crystal structure of 2A has been directly determined from the powder X-ray diffraction data. Interestingly, the crystal packing has been retained during the photoreaction process and, although the powder X-ray diffraction pattern is significantly different, there are only minor structural changes. The comparison of the crystal structures of 1 and 2A reveals the photoreaction mechanism. The lattice energy calculations of the polymorphic forms of 2A and 2B reveals that 2A, which is obtained only by the solid-state photoreaction, is less stable than 2B, which is why it is not reformed on recrystallization.