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A Chichibabin’s Hydrocarbon Based Molecular Cage: The Impact of Structural Rigidity on Dynamics, Stability, and Electronic Properties
Journal of the American Chemical Society ( IF 15.0 ) Pub Date : 2020-06-26 , DOI: 10.1021/jacs.0c04876
Yong Ni 1 , Fernando Gordillo-Gámez 2 , Miriam Peña Alvarez 3 , Zhihan Nan 1 , Zhengtao Li 1 , Shaofei Wu 1 , Yi Han 1 , Juan Casado 2 , Jishan Wu 1, 4
Affiliation  

A 3D π-conjugated polyradicaloid molecular cage c-Ph14, consisting of three Chichibabin's hydrocarbon motifs connected by two benzene-1,3,5-triyl bridgeheads, was synthesized. Compared with its linear model compound l-Ph4, the prism-like c-Ph14 has a more rigid structure, which shows significant im-pact on the molecular dynamics, stability, and electronic properties. A higher rotation energy barrier for the quinoidal biphenyl units was determined in c-Ph14 (15.64 kcal/mol) than that of l-Ph4 (11.40 kcal/mol) according to variable-temperature NMR measurements, leading to improved stability, a smaller diradical character, and an increased singlet-triplet energy gap. The pressure-dependent Ra-man spectroscopic studies on the rigid cage c-Ph14 revealed a quinoidal-to-aromatic transformation along the biphenyl bridges. In addition, the ellipsoidal cavity in the cage allowed selective encapsula-tion of fullerene C70 over C60, with an associate constant of about 1.43×104 M-1. Moreover, c-Ph14 and l-Ph4 exhibited similar redox behavior and their cationic species (c-Ph146+ and l-Ph42+) were obtained by chemical oxidation and the structures were identified by X-ray crystallographic analysis. The bi-phenyl unit showed a twisted conformation in l-Ph42+, whereas remained coplanarity in c-Ph146+. No-tably, molecules of c-Ph146+ form one-dimensional columnar structure via close π-π stacking between the bridgeheads.

中文翻译:

Chichibabin 的碳氢化合物分子笼:结构刚性对动力学、稳定性和电子特性的影响

合成了 3D π 共轭多自由基分子笼 c-Ph14,由三个 Chichibabin 烃基序组成,通过两个苯-1,3,5-三基桥头连接。与其线性模型化合物 l-Ph4 相比,棱柱状 c-Ph14 具有更刚性的结构,这对分子动力学、稳定性和电子性质具有显着影响。根据变温 NMR 测量,在 c-Ph14 (15.64 kcal/mol) 中确定了醌式联苯单元的旋转能垒高于 l-Ph4 (11.40 kcal/mol),从而提高了稳定性,更小的双自由基特征,以​​及增加的单线态-三线态能隙。对刚性笼 c-Ph14 的压力相关拉曼光谱研究揭示了沿联苯桥的醌式到芳香族的转变。此外,笼中的椭圆形腔允许富勒烯 C70 选择性封装超过 C60,相关常数约为 1.43×104 M-1。此外,c-Ph14 和 l-Ph4 表现出相似的氧化还原行为,它们的阳离子物种(c-Ph146+ 和 l-Ph42+)是通过化学氧化获得的,其结构通过 X 射线晶体分析进行鉴定。联苯单元在 l-Ph42+ 中显示出扭曲的构象,而在 c-Ph146+ 中保持共面。值得注意的是,c-Ph146+ 分子通过桥头之间的紧密 π-π 堆积形成一维柱状结构。c-Ph14 和 l-Ph4 表现出相似的氧化还原行为,它们的阳离子种类(c-Ph146+ 和 l-Ph42+)是通过化学氧化获得的,其结构通过 X 射线晶体学分析进行鉴定。联苯单元在 l-Ph42+ 中显示出扭曲的构象,而在 c-Ph146+ 中保持共面。值得注意的是,c-Ph146+ 分子通过桥头之间的紧密 π-π 堆积形成一维柱状结构。c-Ph14 和 l-Ph4 表现出相似的氧化还原行为,它们的阳离子种类(c-Ph146+ 和 l-Ph42+)是通过化学氧化获得的,其结构通过 X 射线晶体学分析进行鉴定。联苯单元在 l-Ph42+ 中显示出扭曲的构象,而在 c-Ph146+ 中保持共面。值得注意的是,c-Ph146+ 分子通过桥头之间的紧密 π-π 堆积形成一维柱状结构。
更新日期:2020-06-26
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