Synthesis and spectroscopic and electrochemical characterization of di- and tetrasubstituted C₆₀ derivatives

The synthesis and electrochemical and spectroscopic characterization of fullerene derivatives of the type R₂C₆₀ where R = C₆H₅CH₂, 2-BrC₆H₄CH₂, 3-BrC₆H₄CH₂, or 4-BrC₆H₄CH₂ and R₄C₆₀ where R = C₆H₅CH₂ are reported. The first step in the synthesis involves an electron transfer between C₆₀^2- and RBr, and a similar initial electron-transfer step occurs between [(C₆H₅CH₂)₂C₆₀] ^2- and C₆H₅CH₂Br during the synthesis of (C₆H₅CH₂)₄C₆₀. On the basis of NMR and UV - visible data, the investigated R₂C₆₀ derivatives are identified as 1,4-adducts of C₆₀, whereas the isolated isomer of (C₆H₅CH₂)₄C₆₀ is characterized as possessing C₁ symmetry with the four benzyl groups being close to each other. The electrochemistry of each synthesized compound was determined in benzonitrile containing 0.1 M tetra-n-butylammonium perchlorate and each mono- and dianion of R₂C₆₀ and R₄C₆₀ were characterized by near-infrared spectroscopy. The near-infrared spectra of each species show two major "marker bands" which can be considered to be diagnostic of the fullerene derivative oxidation state.