Solid-state phase transition of an inclusion complex of 5-methyl-2-pyridone with 1,3,5-benzenetricarboxylic acid.
Solid-state phase transition of an inclusion complex of 5-methyl-2-pyridone with 1,3,5-benzenetricarboxylic acid.
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DOI：
10.1002/anie.200600845
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发表时间：
2006-09
影响因子：
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通讯作者：
S. Hirano;S. Toyota;F. Toda;K. Fujii;H. Uekusa
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文献类型：
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作者：
S. Hirano;S. Toyota;F. Toda;K. Fujii;H. Uekusa
长期以来，人们一直在研究客体化合物在其包合物中与宿主化合物的有效和选择性的分子间和分子内光反应我们报道了5-甲基-(1a)和5-氯-2-吡啶酮（1b）与2,2 ' -联苯二羧酸宿主(2)的1:1包合物的光照射分别得到相应的消旋-顺式-抗二聚体3a和3b。[2,3]这些2-吡啶酮衍生物的[2+ 2]光二聚化反应是DNA损伤的重要模型；这种损伤是由DNA的胸腺嘧啶成分的光二聚化引起的，这是皮肤癌的原因。我们还报道了[4+ 4]2-吡啶酮本身（1c）和1b在其包合物中分别与2和1,2,4,5 -苯四羧酸宿主(4)进行光二聚化，分别得到rac-反式抗二聚体5c和中顺式二聚体6b。[3,4]对这些包合物的x射线分析表明，在所有情况下，2-吡啶酮分子在相应的光二聚化反应中都是有序的。[2-4]然而，在某些情况下，客体分子没有位于光二聚化的适当位置。施密特规则指出，为了在固态中实现有效的光二聚化，两个烯烃分子应该平行排列，并且在晶体中距离小于4.2然而，我们发现，在含有1,3,5 -苯三羧酸(7)的包合物中，光化学不反应的1a分子聚集体可以通过加热或与MeCN蒸气接触在固态下转化为反应性聚集体。x射线分析阐明了这种新型相变的机理。7、1a、MeOH的1∶1包合物(8)由7和1a由MeOH重结晶而成无色晶体，对光照射具有惰性。然而，非常有趣的是，8的晶体通过加热或与MeCN蒸气接触转化为9的活性粉末，其固体光辐射得到中顺式同步[4+ 4]二聚体6a（方案1）。这是第一个在固态中由光化学不反应的分子聚集体转变为反应性聚集体的报告，这是由加热或与溶剂蒸气接触引起的。与EtCN、PhCN、四氢呋喃、丙酮、CH2Cl2、CHCl3或正己烷蒸气接触后，8向9的相变均未发生。这是固体中溶剂效应的一个有趣的例子。据报道，在存在少量溶剂蒸气的情况下，固态反应也有类似的溶剂效应由于6a具有热不稳定性，易于转化为中顺式同步[2+ 2]二聚体11，因此将6a分离为稳定的1:1:1包合物10，该包合物由7、6a和H2O组成，由MeOH光照射后的粉末9重结晶而成。6a与6b.[3]的IR和1H NMR谱进行了比较，对6a的结构进行了鉴定6a的结构最终通过x射线分析10得到证实（图1）。但是，10的模拟粉末x射线衍射（PXRD）模式与光照射后的9不同（见辅助资料）。热不稳定的6a10在cd3good中708℃加热2小时，定量产率为11。通过与3a的1H和13C NMR谱的比较，对11的结构进行了鉴定。[2,3]中位顺式-同步二聚体11是具有顺式-同步结构的2-吡酮[2+ 2]光二聚体的第一个例子。化合物11具有与胸腺嘧啶二聚体相同的结构，这种二聚体是由DNA中核苷酸的胸腺嘧啶组成的光二聚化产生的。要知道非反应性的机理…
Efficient and selective inter-and intramolecular photoreactions of guest compounds in their inclusion complexes with a host compound have long been studied.[1] We reported that photoirradiation of a 1: 2 inclusion complex of 5-methyl-(1a) and 5-chloro-2-pyridone (1b) with a 2, 2’-biphenyldicarboxylic acid host (2) gives the corresponding rac-cis-anti dimer 3a and 3b, respectively.[2, 3] These [2+ 2] photodimerization reactions of 2-pyridone derivatives are important as models for DNA damage; this damage occurs by photodimerization of the thymine component of DNA, which is the cause of skin cancer. We also reported [4+ 4] photodimerizations of 2-pyridone itself (1c) and 1b in their inclusion complexes with 2 and a 1, 2, 4, 5-benzenetetracarboxylic acid host (4), respectively, which give the rac-trans-anti dimer 5c and the meso-cissyn dimer 6b, respectively.[3, 4] X-ray analyses of these inclusion complexes showed that the 2-pyridone molecules are ordered at reasonable positions for the corresponding photodimerization reactions in all cases.[2–4] In some cases, however, the guest molecules are not located at appropriate positions for a photodimerization. Schmidt s rule states that for efficient photodimerization in the solid state, two olefin molecules should be arranged parallel and closer than 4.2 in the crystal.[5] Nevertheless, we found that a photochemically unreactive molecular aggregate of 1a in an inclusion complex with a 1, 3, 5-benzenetricarboxylic acid host (7) can be transformed in the solid state into a reactive aggregate by heating or by contact with MeCN vapor. The mechanism of this novel phase transition was clarified by X-ray analysis. A 1: 1: 1 inclusion complex (8) of 7, 1a, and MeOH, which was prepared as colorless crystals by recrystallization of 7 and 1a from MeOH, was inert to photoirradiation. Very interestingly, however, the crystal of 8 was transformed by heating or by contact with MeCN vapor into a reactive powder of 9, the solid-state photoirradiation of which gave the meso-cis-syn [4+ 4] dimer 6a (Scheme 1). This is the first report of a phase transition in the solid state from photochemically unreactive molecular aggregate into a reactive aggregate caused by heating or contact with solvent vapor. The phase transition of 8 into 9 did not occur by contact with vapor of EtCN, PhCN, tetrahydrofuran, acetone, CH2Cl2, CHCl3, or n-hexane. This is an interesting example of a solvent effect in the solid state. A similar solvent effect was reported for a solid-state reaction that was accelerated in the presence of a small amount of solvent vapor.[6] Since 6a is thermally labile and can be converted easily into the meso-cis-syn [2+ 2] dimer 11, 6a was isolated as its stable 1: 1: 1 inclusion complex 10 consisting of 7, 6a, and H2O, which was prepared by recrystallization of the photoirradiated powder of 9 from MeOH. The structure of 6a was elucidated by comparison of its IR and 1H NMR spectra with those of 6b.[3] The structure of 6a was finally confirmed by X-ray analysis of 10 (Figure 1). However, the simulated powder X-ray diffraction (PXRD) pattern of 10 was different from that of photoirradiated powder of 9 (see the Supporting Information). Heating of the thermally labile 6a as 10 in CD3COOD at 708C for 2 h gave 11 in quantitative yield. The structure of 11 was elucidated by comparison of its 1H and 13C NMR spectra with those of 3a.[2, 3] The meso-cis-syn dimer 11 is the first example of a [2+ 2] photodimer of 2-pyridone that has a cis-syn configuration. Compound 11 has the same configuration as that of the thymine dimer produced by photodimerization of the thymine component of a nucleotide in DNA.[7]To know the mechanism of the unreactive …