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Macrocyclic Polyradicaloids with Unusual Super-ring Structure and Global Aromaticity
Chem ( IF 19.1 ) Pub Date : 2018-05-03 , DOI: 10.1016/j.chempr.2018.03.020
Chunchen Liu , María Eugenia Sandoval-Salinas , Yongseok Hong , Tullimilli Y. Gopalakrishna , Hoa Phan , Naoki Aratani , Tun Seng Herng , Jun Ding , Hiroko Yamada , Dongho Kim , David Casanova , Jishan Wu

π-Conjugated molecules with an annulene-within-an-annulene (AWA) super-ring structure have been pursued by chemists for a long time but with limited success. Here, we report the synthesis of two stable cyclopenta-ring-fused oligo(m-phenylene) macrocycles, 8MC-M and 10MC-M, both showing moderate polyradical character. The octaradicaloid 8MC-M exhibits a [24]annulene-within-[32]annulene structure, which is globally aromatic despite the fact that it possesses 4n π-electrons. Theoretical analyses reveal that the π-electrons in the inner and outer rings follow Baird's rule such that both are triplet biradicals, and overall the molecule is a ground-state spin singlet. The decaradicaloid 10MC-M also possesses a super-aromatic AWA structure with 30 and 40 π-electrons in the inner and outer rings, respectively. However, it has a triplet ground state with a singlet inner ring satisfying Hückel's rule and a triplet outer ring following Baird's rule. Therefore, molecules with a decoupled AWA super-ring structure are eventually attained and also show unusual global aromaticity.



中文翻译:

具有异常超环结构和整体芳香性的大环多基

化学家们长期以来一直在研究具有环-环-环内(AWA)超级环结构的π共轭分子,但获得的成功有限。这里,我们报告两个稳定环戊二烯环的稠合的寡核苷酸(合成亚苯基)大环化合物,8MC-M10MC-M ,二者示出了中等多基字符。八面体类化合物8MC-M表现出[24]环-[32]环中的环结构,尽管它具有4nπ电子,但总体上是芳香族的。理论分析表明,内环和外环中的π电子均遵循贝尔德定律,因此两者均为三重态双自由基,整个分子均为基态自旋单重态。蜕皮类化合物10MC -M还具有内环和外环分别具有30和40个π电子的超芳族AWA结构。但是,它具有三重态基态,其单重态内环满足Hückel规则,三重态外环遵循Baird规则。因此,最终获得了具有解耦的AWA超级环结构的分子,并且还显示出异常的整体芳香性。

更新日期:2018-05-03
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