Effect of metal complexation on ring opening of bowl-shaped hydrocarbons: theoretical study

Density functional theory study on benzenoid and tris-acetylenic structure of fullerene and its fragments shows that tris-acetylenic model structures lead to benzenoid model structure due to the proximity of p-orbitals in the former. The tris-acetylenic model structures are stabilized on metal complexation in comparison to the parent benzene-acetylene equilibrium. In going from Cr to Co, the acetylenic metal complex becomes more stabilized than the benzene-metal complex. The curved surface of the tris-acetylenic fullerene fragments causes one set of π-orbital of the tris-acetylenic groups to rehybridize so as to bend more toward the metal fragments than found in the parent acetylene complexes. This leads to the increased overlap between metal fragments and tris-acetylenic model structures. We also studied the benzenoid and tris-acetylenic model complexes of C<SUB>12</SUB>H<SUB>6</SUB> and C<SUB>12</SUB>H<SUB>12</SUB> where five-membered rings are replaced with more strained four-membered rings