Stabilization of Giant Fullerenes C₂(41)‑C₉₀, D₃(85)‑C₉₂, C₁(132)‑C₉₄, C₂(157)‑C₉₆, and C₁(175)‑C₉₈ by Encapsulation of a Large La₂C₂ Cluster: The Importance of Cluster–Cage Matching

Successful isolation and unambiguous crystallographic assignment of a series of higher carbide cluster metallofullerenes present new insights into the molecular structures and cluster-cage interactions of endohedral metallofullerenes. These new species are identified as La2C2@C2(41)-C90, La2C2@D3(85)-C92, La2C2@C1(132)-C94, La2C2@C2(157)-C96, and La2C2@C1(175)-C98. This is the first report for these new cage structures except for D3(85)-C92. Our experimental and theoretical results demonstrate that La2C92–106 are more inclined to exist stably in the carbide form La2C2@C90–104 rather than as the dimetallofullerenes La2@C92–106, which are rationalized by considering a synergistic effect of inserting a C2 unit into the cage, which ensures strong metal–cage interactions by partially neutralizing the charges from the metal ions and by fulfilling the coordination requirement of the La3+ ions as much as possible.成功分离并精准完成了一系列高阶碳化物簇内嵌金属富勒烯(higher carbide cluster metallofullerenes)的晶体学指认，为内嵌金属富勒烯(endohedral metallofullerenes)的分子结构与簇-笼相互作用研究提供了全新视角。本次研究鉴定出的新型富勒烯物种分别为La₂C₂@C₂(41)-C₉₀、La₂C₂@D₃(85)-C₉₂、La₂C₂@C₁(132)-C₉₄、La₂C₂@C₂(157)-C₉₆以及La₂C₂@C₁(175)-C₉₈。除D₃(85)-C₉₂外，其余上述笼结构均为首次报道。本研究的实验与理论结果证实，La₂C₉₂₋₁₀₆更倾向于以碳化物形式La₂C₂@C₉₀₋₁₀₄稳定存在，而非以双金属富勒烯(dimetallofullerenes)La₂@C₉₂₋₁₀₆的形式存在。这一现象可通过向碳笼内嵌入C₂单元的协同效应得到合理解释：该过程通过部分中和金属离子的电荷、尽可能满足La³+的配位需求，强化了金属与碳笼之间的相互作用。