中科大Shangfeng Yang和厦门大学Su-Yuan Xie研究组在研究中取得进展。他们揭示了通过三角单金属氰化物团簇的相互稳定捕获C₈₄缺失的碳笼异构体。 该研究于2021年5月19日发表于国际一流学术期刊《美国化学会杂志》杂志上。

据悉，单金属氰化富勒烯(CYCFs)是一种仅封装了一个金属原子的内嵌富勒烯的一个独特分支，为阐明其结构与性质的关系提供了一种模型体系，而目前还只分离出了原始CYCFs的C₈₂和C₇₆笼子。C₈₄是最丰富的富勒烯之一，有24个异构体遵循孤立的五边形规则（IPR），其中已经分离出14个异构体，而C_2v(17)-C₈₄异构体的相对能比几个孤立的异构体要低，但从未有过发现为空的和内嵌的富勒烯。

在此，研究人员合成并分离了新的基于C₈₄的原始CYCFs，具有可变的封装金属和异构笼子，包括MCN@C₂(13)-C₈₄ (M = Y, Dy, Tb)和DyCN@C_2v(17)-C₈₄，实现了缺失的C_2v(17)-C₈₄异构体的首次鉴定，C₂(13)-C₈₄异构体经Stone-Wales转化两步可相互转化。

这些基于C₈₄的CYCFs的分子结构是通过单晶x射线衍射确定的。出人意料的是，尽管Y³⁺，Dy³⁺和Tb³⁺的离子半径仅相差0.01，但这种细微的差异导致金属-笼型相互作用的表面发生变化，这是根据金属原子与最近的C₂(13)-C₈₄笼子六边形中心之间的距离推断出的。

另一方面，将异构体笼由DyCN@C₂(13)-C₈₄改为DyCN@C_2v(17)-C₈₄后，DyCN笼间距也发生了变化，说明封装的DyCN笼与外笼之间存在相互作用。因此，课题组证明了CYCFs内部的金属笼间的相互作用可以通过内部和外部的路径进行调节。

附：英文原文

Title: Capturing the Missing Carbon Cage Isomer of C84 via Mutual Stabilization of a Triangular Monometallic Cyanide Cluster

Author: Runnan Guan, Muqing Chen, Jinpeng Xin, Xiao-Ming Xie, Fei Jin, Qianyan Zhang, Su-Yuan Xie, Shangfeng Yang

Issue&Volume: May 19, 2021

Abstract: Monometallic cyanide clusterfullerenes (CYCFs) represent a unique branch of endohedral clusterfullerenes with merely one metal atom encapsulated, offering a model system for elucidating structure–property correlation, while up to now only C82 and C76 cages have been isolated for the pristine CYCFs. C84 is one of the most abundant fullerenes and has 24 isomers obeying the isolated pentagon rule (IPR), among which 14 isomers have been already isolated, whereas the C2v(17)-C84 isomer has lower relative energy than several isolated isomers but never been found for empty and endohedral fullerenes. Herein, four novel C84-based pristine CYCFs with variable encapsulated metals and isomeric cages, including MCN@C2(13)-C84 (M = Y, Dy, Tb) and DyCN@C2v(17)-C84, have been synthesized and isolated, fulfilling the first identification of the missing C2v(17)-C84 isomer, which can be interconverted from the C2(13)-C84 isomer through two steps of Stone–Wales transformation. The molecular structures of these four C84-based CYCFs are determined unambiguously by single-crystal X-ray diffraction. Surprisingly, although the ionic radii of Y3+, Dy3+, and Tb3+ differ slightly by only 0.01 , such a subtle difference leads to an obvious change in the metal–cage interactions, as inferred from the distance between the metal atom and the nearest hexagon center of the C2(13)-C84 cage. On the other hand, upon altering the isomeric cage from DyCN@C2(13)-C84 to DyCN@C2v(17)-C84, the Dy–cage distance changes as well, indicating the interplay between the encapsulated DyCN cluster and the outer cage. Therefore, we demonstrate that the metal–cage interactions within CYCFs can be steered via both internal and external routes.

DOI: 10.1021/jacs.1c02428

Source: https://pubs.acs.org/doi/10.1021/jacs.1c02428