Optical spectra of high-symmetry isomers ₆₀(CH₃-r ₆-H)_n at n=3, 6

Abstract

Earlier, we found the energies of formation and the electron band structures of the fullerene molecule C₆₀ and its methylated and hydrogenated chemical derivatives with saturated r ₆ bonds of the type C₆₀(CH₃-r ₆-H)_n with n from 1 to 6. Based on the self-consistent molecular-orbital method, we found the energies of singlet and triplet excitations for each molecule by the ΔSCF technique. We compared the electron structure of the fullerene molecule with experimental data and other theoretical calculations and showed that the semiempirical quantum-chemical technique used in our work satisfactorily explains the experimental photoluminescence spectra of fullerene-containing star-shaped polystyrenes. Partial or complete removal of the dipole inhibition for the transitions in isomers that are formed upon chemical saturation of double bonds makes it possible to follow changes in the electron structure of the pπ shell of the fullerene molecule by spectroscopic techniques. Specific optical spectra of the first excited singlet states (spectra of absorption, luminescence, and excitation of luminescence) as well as phosphorescence of the first spin-triplet state are described.