Fullerene–Pyrrolidine Biferrocene Donor–Acceptor Triads: Synthesis and Effects of Fullerene[60] on the Electronic Communication of the Two Ferrocene Units in Biferrocene

Abstract

A novel nanoscale molecule, fullerene[60]-based biferrocene (C60-ph-Fc-Fc), was prepared via covalent grafting of biferrocene onto C60 using 1,3-dipolar cycloaddition and was fully characterized by mass spectrometry, nuclear magnetic resonance spectroscopy, infrared spectroscopy, ultraviolet-visible spectroscopy, and fluorescence spectroscopy. Cyclic voltammetry studies showed that C60-ph-Fc-Fc undergoes four successive quasi-reversible processes in the potential window of –2.0~0.40 V (versus Fc+/Fc). The biferrocene (moiety) exhibited significant electronic communication between the two ferrocenyl groups both before and after grafting onto C60. Grafting of fullerene led to weakening in the electronic interaction, and the comproportionation constant decreased by nearly five orders of magnitude from 1.56 × 106 for Fc-Fc to 88 for C60-ph-Fc-Fc, indicating that the electronic communication between halves of the biferrocene could be effectively modified by grafting of C60. The temperature-dependent magnetic susceptibility (2–300 K) study showed that there was a strong antiferromagnetic interaction between the ferrocene FeII centres.