The first representative of a new family of the bridgehead-modified difluoromethylenated homofullerenes: electrochemical properties and synthetic availability

Abstract

The redox properties of the first member of a new family of bridgehead-modified difluoromethylenated homofullerenes, [6,6]-open C60(CF2)H2, were investigated by means of cyclic voltammetry and ESR spectroelectrochemistry. The half-life time of C60(CF2)H2–• estimated from the decay of the ESR response exceeds 25.5min at room temperature which will be crucial for practical applications later on. The high stability of C60(CF2)H2–• was proven to be attributed to spin density delocalization over the fullerene cage as well as to the higher BDE(C–H) value for C60(CF2)H2 (as compared to C60H2). Di- and trianions of C60(CF2)H2 are less stable and undergo partial dehydrogenation. A detailed voltammetric investigation of H-transfer processes (induced by radicals, radical-anion species or by a Brønsted bases) in the anionic forms of C60(CF2)Hm (m=0–2) was performed. It allowed suggesting a general scheme integrating various anionic forms of C60(CF2)Hmn– (n=1–3) which was corroborated by DFT calculations as well as by a targeted synthesis of deprotonated C60(CF2)H– and C60(CF2)2– anions from C60(CF2)H2 using a Brønsted base.Based on these results, an alternative, non-electrochemical synthetic route to C60(CF2)H2 using the Zn/Cu-couple in water/toluene media was elaborated since similar processes regulate the features of hydrogenation of fullerene derivatives in both cases.