Polyyne cyclization to form carbon cages: [16.16.16](1,3,5)cyclophanetetracosayne derivatives C60H6 and C60Cl6 as precursors to C60 fullerene

[16.16.16](1,3,5)Cyclophanes fused by six [4.3.2]propellatriene units, which would serve as precursors to cage polyyne C60H6 and its perchloro derivative C60Cl6, respectively, were prepared. In the negative mode laser desorption mass spectra of the cyclophanes, the polyyne anions C60H6− and C60Cl6− were detected. Moreover, size-selective formation of C60+ as well as C60− was also observed, indicating the possible polyyne cyclization mechanism to form the fullerene cage.