Electrochemical behavior and parameters of hydrofullerene C60H36

Abstract

Electrochemistry of hydrofullerene C6oH36 was studied by cyclic voltammetry in TH F and CH2CI_~ in the -47--14 ~ temperature range. Hydrofullerene undergoes reversible oneelectron reduction to form a radical anion in THF (E ~ = -3.18 V (Fc~ Fc = ferrocene) and irreversible one-electron oxidation in CH2C12 (Ep a = 1.22 V (Fc~ The reduction potential was used to estimate electron affinity of hydrofullerene as EA = -0.33 eV. It was suggested that C60H30 is an isomer with T-symmetry in which 12 double bonds form four isolated benzenoid rings located in vertices of an imaginary inscribed tetrahedron on the molecular surface. For hydrofullerene, the ~electrochemical gap" is an analog of the energy gap (HOMO--LUMO), equal to (E ~215 -E ~r = 4.4 V, and indicates that C60H36 is a sufficiently "hard" molecule with a low reactivity in redox reactions.Key words: hydrofullerene, C60H36 . redox properties, cyclic voltammetry, electron affinity, electrochemical gap.Presently, C60H 2 and C70H 2 are the only electrochemically characterized I hydrofullerenes. It is established 2,3 that, similarly to fullerenes, the reduction of hydrofullerenes includes several one-electron, mainly reversible, steps, but with potentials 100--180 mV more negative than those for the corresponding fullerenes. In addition, C60H2 undergoes irreversible two-electron oxidation accompanied by the ejection of two protons followed by regeneration of C60 .1,2 Hydrofullerenes with a higher content of hydrogen were not electrochemically characterized. Perhaps, this is related to their very low solubility in most solvents appropriate for electrochemical studies.Electrochemistry and reactivity of both hydrofullerenes and their radical ion states are of doubtless interest. In addition to information on the reactivity of electrogenerated radical ions, these data provide valuable information on boundary orbitals (HOMO, LUMO, etc.). The problem of the structure of hydrofullerene C60H36 remains unclear up to now. 4,s The theoretical calculations predict that hydrofullerene C60H36 has 1013 isomers. 6 The four most stable isomers of hydrofullerene C60H3o with T-, Th-, D3a-, and D3a--symmetry are considered in the literature. They differ in arrangement of 12 double bonds on the molecular surface which remain after hydrogenation of C60 (Fig. 1). In the isomer with T-symmetry, 12 double bonds form four isolated benzene rings located in vertices of an imaginary inscribed tetrahedron on the molecular surface. In the isomer with Th-symmetry, 12 isolated double bonds are arranged in five-membered tings, whereas in the isomers With D3d-and D3a,-symmetry, six double bonds are located on poles of the molecule as benzene rings, and the other six double bonds are parallel to the equator of the molecule (D3d) or are arranged at an angle to the equator (D3d.). Our studies of C60H36 by 13C and IH NMR, 4,s X-ray photoelectron, and emission spectroscopy 7,s showed that the hydrofullerene is, most probably, an isomer with T-symmetry. Electrochemical study of hydrofullerene can provide ad...

Multi‐Redox Active Carbons and Hydrocarbons: Control of their Redox Properties and Potential Applications

“…To date, various multi‐redox active C x H y molecules have been explored. These include, but are not limited to, nanographenes, [16–24] radicaloids (mostly based on diindenoarenes), [25–34] macrocycles, [35–39] fullerene fragments (including buckybowls), [40–45] nanographene‐buckybowl hybrids, [46] pentalene derivatives, [47] ethynylenes, [48] spiro‐compounds, [14] cumulenes, [49] other C x H y molecules with either the azulene, [50] barrelene, [51] fluoranthene, [52] fluorene, [53] diphenalene, [54] phenylene, [55] or Schwarzite framework, [56] and hydrofullerenes [57–61] . The redox properties of dissolved C x H y molecules are summarized in Table 1, where C x H y molecules that show at least six redox reactions (Scheme 1) are listed.…”

“…Lobach et al. synthesized C 60 H 36 by hydrogen transfer from 9,10‐dihydroanthracene to C 60 and measured its amphoteric redox behavior [60] . C 60 H 36 presented one redox couple at negative potentials and one irreversible oxidation reaction.…”

22 Fullerenes

“…135 The electrochemistry of C 60 H 36 has been studied and a reversible one-electron reduction forming a radical anion observed. 136 The hydrogenation of the simplest fulleroid, C 61 H 2 , yielding two isomers of C 61 H 4 has been performed using either a Zn/Cu couple or hydroboration. 137 The regioisomers formed are dictated by the hydrogenation technique employed and preferred reaction takes place at one of the two double bonds containing a bridgehead carbon.…”

Dependence of the Electrochemical Redox Properties of Fullerenes on Ionic Liquids

“…, C 60 H x ) is more negative than that of the corresponding pristine fullerene ( e.g. , C 60 ) because of the increase in the number of hydrogen atoms on the fullerene cage. − Furthermore, the electrochemical properties of fullerene derivatives depend on the functional groups linked to the fullerene cages. Hence, the change in the electrochemical properties and the electron affinity of a fullerene derivative can be predicted based on the functional groups used for its chemical modification.…”