Open-Cage Fullerenes: Synthesis, Structure, and Molecular Encapsulation

Abstract

The carbon-carbon bond scission of the fullerene cage offers an open-cage fullerene derivative having an opening on the fullerene surface. This account summarizes our recent studies on the syntheses of open-cage C 60 derivatives as well as their properties of molecular encapsulation. The photochemical rearrangement of the cyclohexadiene derivative of C 60 gives bis(fulleroid), the precursor for the cage scission. The photooxygenative carbon-carbon bond cleavage of bis(fulleroid) affords an open-cage diketone derivative having a 12-membered ring. The reaction of the diketone derivative with aromatic hydrazine or hydrazone allows the ring expansion of the orifice by regioselective cage scission to yield a product bearing a 16-membered ring. The orifice in the product is large enough to pass a hydrogen molecule, producing an endohedral hydrogen complex. In the case of the reaction with ortho-phenylenediamine, two carbon-carbon bonds are sequentially cleaved to afford a product having a 20-membered ring orifice. This product spontaneously encapsulates one water molecule to form an endohedral water complex. Hydrogen (H 2 ) 4.2 Water 5Conclusion and Future Aspects

Hydrolysis‐Initiated Domino Process on the Rim of Open‐Cage C60 Derivatives Including Decarbonylation and Double Dehydration

“…Due to the unique spherical structure of the fullerene cage, functional groups on the rim of the orifice usually exhibit unusual reactivity differing from that of classical organic compounds. For example, the orifice‐expansion reactions reported by Iwamatsu and Yeh are very efficient in making open‐cage fullerenes with a very large orifice. But these reactions are observed only for open‐cage fullerenes not for normal organic compounds.…”

Preparation of Open‐Cage Fullerenes and Incorporation of Small Molecules Through Their Orifices

“…[44] The reaction of amino-compounds with open-cage fullerene derivatives is an efficient method to form large holes capable of incorporating small molecules. [52] Iwamatsu and coworkers found that hydrazine or hydrazone or phenylenediamine reacted with the ketolactam 25 to form compounds 44 [53] and 45.…”

Open‐cage fullerenes as tailor‐made container for a single water molecule

“…It was prepared in four steps in a total of 33% (2a) or 38% (2b) yield from [60]fullerene. [26][27][28] Orifice expansion of a singlet oxygen oxidized precursor 1 with 1,2-phenylenediamine is the key step for the formation of 20-membered ring orifice in this compound. Structures of 2 were assigned by spectroscopic data.…”