Synthesis and characterization of highly ordered self-assembled bioactive fulleropeptides

A series of N-substituted fulleropyrrolidines containing peptide side chain was synthesized by the quantitative, TFA-mediated deprotection of the corresponding tert-butyl esters. The structures of all compounds were determined by comparative analysis of spectroscopic and spectrometric data. The electrochemical characterization, conducted by cyclic voltammetry at room temperature confirmed slightly attenuated reducibility in comparison to pristine C-60 and a weak long-range electron-accepting effect of the Gly(3)-fragment. The introduction of the peptide subunit led to improved solubility and enabled examination of the antioxidant properties in water environment. A notable radical scavenging activity of the fullerene subunit remained almost unchanged in all compounds. The investigation of the supramolecular self-assembling, performed by the scanning electron microscopy revealed an influence of the side chain, particularly the fraction of the hydrophobic residue, as well as the substrate structure on the final morphology. Most of the compounds underwent highly ordered multi-stage hierarchical assembling to the attractive, flower-shaped supramolecular aggregates during both the precipitation and slow evaporation of the solvent.