Pentagon-fused hollow fullerene in C78 family retrieved by chlorination.

C(78) is one of the most widely investigated higher fullerenes. Among its huge isomer family, only one non-IPR (IPR = isolated pentagon ring) cage, the C(2)-symmetric (#22010)C(78), was previously stabilized by endohedral derivatization. Here we report a new C(1)-symmetric non-IPR hollow isomer, (#23863)C(78), which was captured as (#23863)C(78)Cl(8) and then subjected to a regioselective substitution reaction with benzyl hydroperoxide to form (#23863)C(78)(OOCH(2)C(6)H(5))Cl(7). The structural connectivity of (#23863)C(78), which contains a pair of fused pentagons, was confirmed by single-crystal X-ray diffraction analysis of the (#23863)C(78)(OOCH(2)C(6)H(5))Cl(7) molecule, which shares the same fullerene core with (#23863)C(78)Cl(8); support for the structure is provided by comparable IR measurements and computation. Theoretical studies suggest that the differences in C-Cl bond length, intermediate stability, and steric effects of the involved molecules account for the chemical regioselectivity of the substitution reaction.