The structure and stability of catecarbynes, i.e., nonlinear C carbynes 60 Ε½ . of the link catenane type, have been established by ab initio calculations. For each C 60 catecarbyne topological type examined, the energy changes evaluated with the Ε½ . components size varying in the series C C , where 20 G n G 5, which exhibit one 60y2 n 2 n to several minima, have been shown to depend on the number of crossings and structure type. For the 2 2 C catecarbyne, the lowest structure is built from two cyclic carbynes of 1 60 the same size but, for the 4 2 C catecarbyne, the two minimum energy structures are 1 60 those composed of the C and C cycles and the 4 2 C C molecule is the local 24 36 1 30 30 maximum structure. For the 5 2 C catecarbyne, the minimum energy structure is 1 6 0 constructed from the C and C cycles and the local maximum structure is formed 20 40
when the first and the second cycles have 42 and 18 C atoms, respectively. The Ε½ 2 2 2 . six-crossings catecarbynes 6 , 6 , and 6 exhibit an even more complex behavior. Such 1 2 3 relationships show that, for the same topological catenane type with several crossings, some structures may be more stable by several hundreds of kilocaloriesrmole than others.