Characterization of Six Isomers of [84]Fullerene C84 by Electrochemistry, Electron Spin Resonance Spectroscopy, and Molecular Energy Levels Calculations

The electrochemical and electron spin resonance (ESR) fingerprints of six isomers of C84 [D 2(IV), D 2 d (II), D 2 d (I), D 2(II), C 2(IV), and C s (b)] are presented together with density functional theory (DFT) calculations of the molecular orbitals (MO) energy levels for a total of 10 isomers (D 2(IV), D 2 d (II), D 2 d (I), D 2(II), C s (V), and C 2(I) to C 2(V)). Comparison between calculations and electrochemical data shows a true synergy between calculated energy levels and experimental redox potentials. Assignments are proposed of the C 2 isomer as C 2(IV) and tentatively of the C s (b) isomer as C s (V). The temperature-dependent ESR spectra of D 2(IV) and D 2 d (II) singly charged ions show an abrupt change around 150 K which is ascribed to a change of spin state. Additionally, the room-temperature solution ESR spectra of all isomers studied exhibit a fine structure characteristic of each isomer.