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 [D₂(IV), D_2d(II), D_2d(I), D₂(II), C₂(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 (D₂(IV), D_2d(II), D_2d(I), D₂(II), C_sV), and C₂(I) to C₂(V)). Comparison between calculations and electrochemical data shows a true synergy between calculated energy levels and experimental redox potentials. Assignments are proposed of the C₂ isomer as C₂(IV) and tentatively of the C_s(b) isomer as C_s(V). The temperature-dependent ESR spectra of D₂(IV) and D_2d(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.