D2d(23)-C84 versus Sc2C2@D2d(23)-C84: Impact of Endohedral Sc2C2 Doping on Chemical Reactivity in the Photolysis of Diazirine

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• 作者：Michio Yamada ; Yukiko Tanabe ; Jing-Shuang Dang ; Satoru Sato ; Naomi Mizorogi ; Makoto Hachiya ; Mitsuaki Suzuki ; Tsuneyuki Abe ; Hiroki Kurihara ; Yutaka Maeda ; Xiang Zhao ; Yongfu Lian ; Shigeru Nagase ; Takeshi Akasaka
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：December 21, 2016
• 年：2016
• 卷：138
• 期：50
• 页码：16523-16532
• 全文大小：619K
• ISSN：1520-5126

文摘

We compared the chemical reactivity of D_2d(23)-C₈₄ and that of Sc₂C₂@D_2d(23)-C₈₄, both having the same carbon cage geometry, in the photolysis of 2-adamantane-2,3′-[3H]-diazirine, to clarify metal-atom doping effects on the chemical reactivity of the carbon cage. Experimental and computational studies have revealed that the chemical reactivity of the D_2d(23)-C₈₄ carbon cage is altered drastically by endohedral Sc₂C₂ doping. The reaction of empty D_2d(23)-C₈₄ with the diazirine under photoirradiation yields two adamantylidene (Ad) adducts. NMR spectroscopic studies revealed that the major Ad monoadduct (C₈₄(Ad)-A) has a fulleroid structure and that the minor Ad monoadduct (C₈₄(Ad)-B) has a methanofullerene structure. The latter was also characterized using X-ray crystallography. C₈₄(Ad)-A is stable under photoirradiation, but it interconverted to C₈₄(Ad)-B by heating at 80 °C. In contrast, the reaction of endohedral Sc₂C₂@D_2d(23)-C₈₄ with diazirine under photoirradiation affords four Ad monoadducts (Sc₂C₂@C₈₄(Ad)-A, Sc₂C₂@C₈₄(Ad)-B, Sc₂C₂@C₈₄(Ad)-C, and Sc₂C₂@C₈₄(Ad)-D). The structure of Sc₂C₂@C₈₄(Ad)-C was characterized using X-ray crystallography. Thermal interconversion of Sc₂C₂@C₈₄(Ad)-A and Sc₂C₂@C₈₄(Ad)-B to Sc₂C₂@C₈₄(Ad)-C was also observed. The reaction mechanisms of the Ad addition and thermal interconversion were elucidated from theoretical calculations. Calculation results suggest that C₈₄(Ad)-B and Sc₂C₂@C₈₄(Ad)-C are thermodynamically favorable products. Their different chemical reactivities derive from Sc₂C₂ doping, which raises the HOMO and LUMO levels of the D_2d(23)-C₈₄ carbon cage.