Theoretical Structural and Spectral Analyses of TEMPO Radical Derivatives of Fullerene

Abstract

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