Theoretical Structural and Spectral Analyses of TEMPO Radical Derivatives of Fullerene

The spectroscopic properties of the 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) radical derivatives of the fullerene (C60) were theoretically investigated. The ground state optimized structures of the radical adducts of the fullerene were calculated by using DFT (B3LYP) with 6-31 G(d) level. It was concluded that a 6-6 ring junction of C60 moiety generally covalently links to the piperidine ring of the TEMPO derivatives, directly. The optimization characteristics of all the fullerene radical derivatives indicate generally a annulene structure while C60+TEMPO indicate a cyclopropane structure which is formed by the link of the carbon of the piperidine ring doubly to a 6- 6 ring junction of C60. The calculated isotropic hyperfine coupling constants, vibrational frequencies and UV- Vis transition energies of all the radical adducts were seen to be in good agreement with the corresponding experimental data. The UV-Vis transitions and their energies were determined with corresponding to the experimental values. In the IR analysis the shifts of vibrational frequencies have been commented by comparison with those belonged to the pure C60. Also the some selected geometrical parameters with together the cage width and the cage length for the ground state optimized structures of all the radical adducts were listed, and the binding energies of the radicals were obtained.