Polarity-Dependent Isomerization of an Unsymmetrical Overcrowded Ethylene Promoted by Zwitterionic Contribution in the Twisted Isomer
Polarity-Dependent Isomerization of an Unsymmetrical Overcrowded Ethylene Promoted by Zwitterionic Contribution in the Twisted Isomer
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DOI：
10.1002/asia.201701805
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发表时间：
2018-03-02
影响因子：
4.1
通讯作者：
Kubo, Takashi
中科院分区：
文献类型：
--
作者：
Hirao, Yasukazu;Nagamachi, Nobuhiro;Kubo, Takashi
双蒽酮的扭曲形式被认为是由折叠形式的光诱导或热诱导异构化提供的亚稳态，因此阻止了其电子结构的分离和详细分析。在本研究中，一个不对称的双蒽酮（2），由吸电子蒽酮和给电子吖啶组成，已被合成，并显示出溶剂极性依赖的折叠和扭曲异构体之间的异构化反应。随着溶剂极性的增加，2发生了从折叠态到扭曲态的异构化反应。扭转异构体在极性溶剂中的稳定性可以解释为其相对较大的两性离子特征的证据。2的DMF溶液显示顺磁加宽的NMR信号，从热填充的三重态产生的旋转的扭曲异构体的弱化的烯属双键。
The twisted form of bianthrone is known as a metastable state provided by a photo-induced or thermal-induced isomerization of the folded form, and thus prevents the isolation and the detailed analysis of its electronic structure. In this study, an unsymmetrical bianthrone (2), consisting of the electron-withdrawing anthrone and electron-donating acridane, have been synthesized and shown to exhibit a solvent-polarity-dependent isomerization reaction between the folded and twisted isomers. With increasing the polarity of the solvent, 2 showed an isomerization reaction from the folded form to the twisted form. The stabilization of the twisted isomer in polar solvents can be interpreted as proof of its relatively large zwitterionic character. The DMF solution of 2 displayed paramagnetically-broadened NMR signals from the thermally populated triplet state resulting from rotation of the weakened ethylenic double bond of the twisted isomer.