Cyclopentene-fused [C60]-fullerenes: synthesis and electrochemical properties

New cyclopentene-fused [C60]-fullerene derivatives containing terpene moieties have been synthesized by [3 + 2]-addition to fullerene C₆₀. All obtained products were fully characterized by ¹H- and ¹³C-NMR, IR, and MS. The electrochemical properties have been studied by cyclic voltammograms (CV), combined with absorption spectra, which are consistent with those obtained from density functional theory (DFT) calculations. It was found that all fulleropyrrolidines showed very similar absorption spectra, orbital energies, in which electron densities in both the LUMO and HOMO are mainly located on the fullerene cage, suggesting that C₆₀ act as the acceptor. All the compounds exhibited good thermal stability. All determined characteristics of fullerene conjugates were compared to [6,6]-phenyl-C61-butyric acid methyl ester ([60]PCBM), a popular fullerene-containing compound. Graphical abstract: .