Features of molecular structure of small non-IPR fullerenes: the two isomers of C50

Here for the first time, we applied approach developed earlier for higher fullerenes to investigate the features of molecular structures of non-IPR isomers 270 (D3) and 271 (D5h) of small fullerene C50. The bond distributions are presented as structural formulas. The instability of the studied isomers is caused by a significant local overstrain due to the excessive folding of pentagons in pentalene fragments, which typically are planar molecules. It is found that the chains of π-bonds are passing through some cycles like in the previously studied higher non-IPR fullerenes C66 and C68. Chemical shifts of the centers of the pentagons and hexagons (NICS(0)) are reported. It is shown that chlorine atoms in the exohedral derivative C50Cl10 of isomer 271 (D5h) are attached to the indacene-like substructures confirming the preference of addition to π-delocalized hexagons in radical reactions. The identified features in the structures of smaller fullerene molecules can be predictive of the ability to be synthesized as derivatives and will assist in determination of their reactivity.