Triplet molecules of the D5 symmetry group based on C60 fullerene

The possibility of observing a non-zero-spin triplet state in highly symmetric derivatives of fullerene molecules with five double bonds, representing isomers of the type D₅-C₆₀(R-r ₆-R)₅ (where R = H or CH₃), is assessed based on the results of quantum-chemical calculations. The energies of isomer formation (endo-and exothermal process for the hydrogenated and methylated isomers, respectively) and the energies of terms are determined. The ground state corresponding to a non-zero-spin triplet e ₁ ² (³A₂) occurs approximately 0.3 eV below the zero-spin states. The results can be interpreted within the framework of the tight binding approximation for the pπ basis set orbitals of fullerene molecules (representing radially directed C2p hybrid atomic orbitals). The character of the open electron shell of isomers, delocalized over a large fullerene surface, suggests that, with high probability, the above non-zero-spin triplet state (rather than the e ₁ ² (¹E₂) state stabilized by the Jahn-Teller effect) is the ground state of the system.