A 4/6/8 Structural Pattern: Computations on C48

An alternative structural pattern for fullerenes, inclusion of four-membe-red rings, is studied on the C48 case. The truncated cuboctahedron-like structure is computed (four-, six -and eight-membered rings) at semiempirical level (MNDO, AM1, SAM1). Although the structure is a local energy minimum, it is located more than 1000 kJ/mol above a pentagon/hexagon C48 structure (1500 kJ/mol in the SAM1 method). Owing to a high symmetry (Oh) the computed IR spectrum is relatively simple. The inclusion of the four-membered rings can be particularly significant with heterofullerenes and possibly with odd-numbered fullerenes.