Characterization and structures of dimeric C₇₀ oxides, C₁₄₀O, synthesized with hydrothermal treatment

The dimeric C₇₀ oxides were synthesized from C₇₀/C₇₀O mixed powder by hydrothermal treatment at 373 K for 12 h in aqueous NaOH solution. In this treatment, nucleophilic OH^- ions are abundant and nucleophilic addition reactions were considered to synthesize dimeric fullerene oxides. The yield was estimated as ca. 2-3% summing up each isomer and also produced polyoxides, it is lower than that of C₁₂₀O. Three isomers of C₁₄₀O were isolated using High Performance Liquid Chromatography (HPLC) and characterized with UV-vis, FT-IR, and ¹³C NMR and other methods. The results of these methods show a close similarity between C₁₄₀O and C₁₂₀O and support that our C₁₄₀O samples exhibit the structure of conventional furan-bridged dimers. On the basis of the results of ¹³C NMR and PM3 calculations, structure assignments for each sample were attempted.