每周分子 | Molecule of the Week

Original ACS 美国化学会 ACS美国化学会 2022-07-05

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每周分子：无穷烯

Molecule of the Week: Infinitene

无穷烯是由12个苯环稠合连接成的一个形似无穷符号(∞)的稠环芳烃，或者将其旋转90°，则像数字8。经过多年的期待，无穷烯于2021年由日本名古屋大学的Maciej Krzeszewski、Hideto Ito和Kenichiro Itami成功合成。其正式化学名称如文末信息速览表所示；也可被称为：

cyclo[c.c.c.c.c.c.e.e.e.e.e.e]dodecakisbenzene。

无穷烯的结构也可以看作是两个稠合的[6]螺旋烯单元。当然，[6]螺旋烯是螺旋状的，有两个手性相反的对映异构体。要形成无穷烯，两个[6]螺旋烯对映体必须具有相同的手性，因此，无穷烯也有两个对映异构体，分别用(+)-(P,P)和(-)-(M,M)表示。轴手性符号(P)和(M)分别代表 “正”或“右手”和“负”或“左手”。

合成无穷烯后，Krzeszewski等科学家对无穷烯进行了所有必要的光谱研究来确定其结构。他们还计算了每个苯环的芳香度; 不过他们未报道整个无穷烯分子是否具有芳香性。随后，芬兰赫尔辛基大学的Mesías Orozco-Ic、Rashid R. Valiev和Dage Sundholm通过复杂的计算证明无穷烯具有芳香性；当施加外部磁场时，会在无穷烯分子边缘产生两条不相交的电流密度通道。

无穷烯的合成在化学家当中引起了相当大的轰动，《C&EN》(《化学与工程新闻》杂志)将其评选为2021年的年度分子。

无穷烯信息速览

CAS 登记号	Racemic: 2744250-32-4 (P,P): 2744371-11-5 (M,M): 2744371-12-6
SciFinder命名	10,21,9,22-[1,3,5]Hexatriene[1,3,4,6] tetrayldiphenanthro[3,4-c:3′,4′-l]chrysene
分子式	C₄₈H₂₄
摩尔质量	600.70 g/mol
外观	带绿色荧光的黄色固体
熔点	未见报道
水溶性	不可溶

【关于每周分子】

自2001年以来，“每周分子”已成为广受欢迎的栏目。多数分子由读者推荐。每个结构都经由科学家审查，并以3-D和平面图像的形式显示，同时附有该分子简介。可以通过美国化学文摘社 (CAS) 提供的SciFinder中的CAS REGISTRY获取“每周分子”的更多信息。CAS REGISTRY中的每条物质信息都展示了物质的CAS登记号、索引名、通用名、商品名、书目信息等其他更多信息。发送邮件至motw@acs.org推荐您感兴趣的分子吧。

Infinitene is a chain of 12 fused benzene rings that forms an infinity symbol (∞) or, rotated 90°, a figure 8. After years of anticipation, it was synthesized in 2021 by Maciej Krzeszewski, Hideto Ito*, and Kenichiro Itami* at Nagoya University (Japan). Its official chemical name is in the fast facts table; but it is also known by the daunting term:

cyclo[c.c.c.c.c.c.e.e.e.e.e.e]dodecakisbenzene.

The structure of infinitene can also be thought of as two fused [6]helicene units. [6]Helicene is, of course, helical, and thus exists in two enantiomeric isomers with opposite chirality. To complete the infinitene loop, both helicenes must be of the same chirality, so that infinitene also exists in two enantiomers, designated as (+)-(P,P) and (–)-(M,M). The axial chirality symbols (P) and (M) stand for “plus”, or “right-handed”, and “minus”, or “left-handed”, respectively.

After synthesizing infinitene, Krzeszewski et al. performed all the necessary spectroscopic studies to confirm its structure. They also calculated the aromaticity of each benzene ring; but they did not report whether the entire molecule is aromatic. Subsequently, Mesías Orozco-Ic, Rashid R. Valiev, and Dage Sundholm at the University of Helsinki used sophisticated calculations to show that the molecule is aromatic; when an external magnetic field is applied, it creates two non-intersecting current density pathways along the molecules’ edges.

The synthesis of infinitene generated considerable buzz among chemists. C&EN readers voted it molecule of the year for 2021.

Infinitenefast facts

CAS Reg. No.	Racemic: 2744250-32-4 (P,P): 2744371-11-5 (M,M): 2744371-12-6
SciFinder nomenclature	10,21,9,22-[1,3,5]Hexatriene[1,3,4,6] tetrayldiphenanthro[3,4-c:3′,4′-l]chrysene
Empirical formula	C₄₈H₂₄
Molar mass	600.70 g/mol
Appearance	Yellow solid with green fluorescence
Melting point	Notreported
Water solubility	Not reported

About Molecule of the Week

MOTW has been a popular feature on ACS website since 2001. Many molecules are suggested by our website visitors. Every structure is reviewed by a scientist and displayed in 3-D and flat images with a brief description. Each week’s molecule also links to a sample record from the CAS REGISTRY, which is searched using SciFinder. Each record displays the registry number, index name and synonyms, bibliographic information, and more. Send us a molecule suggestion at motw@acs.org.

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