Synthesis of Fullerene Oxides Containing Both 6,6-Closed Epoxide and 5,6-Open Ether Moieties through Thermolysis of Fullerene Peroxides

Epoxy and Oxidoannulene Oxidation Mechanisms of Fused-Pentagon Chlorofullerenes: Oxides Linked by a Pirouette-Type Transition State

Recently, the oxidative functionalization of double-fused-pentagon (DFP)-containing chlorofullerenes ^#271C₅₀Cl₁₀ and ^#913C₅₆Cl₁₀ was carried out, resulting in two monoepoxides with the oxygen atom added at the ortho site of pentalene on the DFP moiety. To uncover the reactivity of isolated-pentagon-rule violating fullerenes upon oxidation, two possible formation processes (ozone molecule and oxygen radical served as oxidation reagents) of these two oxides were systematically investigated through density functional theory calculations. For the ozone oxidation, two possible pathways were explored, and the results indicate that the biradical mechanism Path_os-RACDP is kinetically more favorable than Path_os-RABP, where R, A, and P represent reactants, ozonide intermediates, and oxidation products and B, C, and D represent another three oxygen-containing intermediates. The products obtained by ozone oxidation ([6,6]-55-closed epoxides P-C₃-C₂₉ for ^#271C₅₀Cl₁₀ and P-C₄₂-C₄₃ for ^#913C₅₆Cl₁₀ with oxygen atom added at the shortest and highest HOMO-contribution bonds) are consistent with experimental observations. However, the oxygen radical additions on these two chlorofullerenes favor generation of the [5,6]-66-open oxidoannulene adducts P-C₃-C₂ and P-C₄₂-C₅₄, respectively. Subsequent analyses of their geometrical features and structural stabilities suggest that these two oxidoannulene adducts are energetically unfavorable and could be converted to more stable epoxides mentioned above by undergoing a pirouette-type transition state. In these two diverse oxidation procedures, the favorable C-C bonds for ozone attacking and C atoms for oxygen-adsorption are rationalized in terms of their bond lengths and HOMO contributions as well as pyramidalization angles.

Regioselective Oxidation of Fused-Pentagon Chlorofullerenes

Two monoxides of typical smaller chlorofullerenes, (#271)C50Cl10O and (#913)C56Cl10O, featured with double-fused-pentagons, were synthesized to demonstrate further regioselective functionalization of non-IPR (IPR = isolated pentagon rule) chlorofullerenes. Both non-IPR chlorofullerene oxides exhibit an epoxy structure at the ortho-site of fused pentagons. In terms of the geometrical analysis and theoretical calculations, the principles for regioselective epoxy oxidation of non-IPR chlorofullerenes are revealed to follow both "fused-pentagon ortho-site" and "olefinic bond" rules, which are valuable for prediction of oxidation of non-IPR chlorofullerenes.

A precision structural model for fullerenols

An explicit structural model was developed and verified for fullerenols.

Preparation of a 12-membered open-cage fullerendione through silane/borane-promoted formation of ketal moieties and oxidation of a vicinal fullerendiol

[60]Fullerene mixed peroxide C(60) (OH)(Cl)(OOtBu) reacts with PhMe(2)SiH/B(C(6)F(5))(3) to give oxahomofullerene. Mechanistic investigation indicates that the hydroxyl group in the central pentagon ring is essential to convert the tert-butylperoxo group into a ketal moiety. Migration of the silyl group and transformation of the siloxy group into a phenyl group are observed in the deprotection of the fullerene bound siloxy group. A 12-membered open-cage fullerendione was obtained through oxidation of a [6,6]-fullerendiol. This orifice could be closed to form ketal/hemiketal moieties by BF(3)-catalyzed reaction with methanol. All of the new fullerene derivatives were characterized by spectroscopic data, and structure of the open-cage fullerendione was also confirmed by single-crystal X-ray analysis.

Preparation of open-cage fullerenes and incorporation of small molecules through their orifices

Open-cage fullerenes can act as hosts for small molecules such as water, nitrogen, or hydrogen, forming endohedral fullerenes. Following a brief summary of carbon, nitrogen, and oxygen insertion in the fullerene framework to form homofullerenes, methods of creating a hole in the fullerene surface are surveyed. Techniques of hole enlargement and the insertion of atoms or molecules through the orifice to form endohedral fullerenes are described. Finally, the possibility of subsequent closure of the hole is considered.