Computations on C 84O: thermodynamic, kinetic and photochemical stability

Abstract

Fullerene oxides were the first observed fullerene derivatives and they have naturally attracted attention of both experiment and theory. C 60O has represented a long standing case of experiment–theory disagreement, and there has been a similar problem with C 60O 2—both cases were explained by kinetic rather than thermodynamic control. In this contribution, we report the first computations of C 84O. The computations are carried out with the PM3 quantum-chemical semiempirical method. Thermodynamic stabilities are evaluated for the electronic singlet and triplet states. The triplet states are computed at both restricted open-shell Hartree–Fock (ROHF) and unrestricted open-shell Hartree–Fock levels. The computations focus on the two most abundant C 84 isomers— D 2 and D 2 d , and especially deal with additions to their shortest and longest bonds. The D 2/long structure is the lowest-energy species. The PM3/ROHF energy ordering of the C 84O isomers in the first triplet electronic state is exactly the same as in the singlet electronic state and the relative energies are also quite similar. On the other hand, the kinetic stability order is just reversed compared to the thermodynamic order. Hence, for relatively short reaction times the C 84O D 2/short isomer should primarily be formed (in spite of the fact that it should be, thermodynamically, the least stable in the studied set). The computations point out various stability selection rules controlling production of fullerene-based materials.