C60 dimers connected through pleiadene bridges: fullerenes talking to each other

Abstract

New C₆₀ dimers 1, 2 and 3 that differ in the distance between the two balls, connected through pleiadene bridges have been synthesized. Different synthetic strategies have been used to prepare C₆₀ dimers 1–3. A diastereoisomeric mixture was obtained for C₆₀ dimer 1, which was separated by column chromatography and characterized by NMR. By CV measurements, no interaction between the two balls was found in the ground state in any type of C₆₀ dimer. By reduction with dimeric benzylnicotinamide [(BNA)₂], a two electron reductant, the interaction between both C₆₀ units has been analyzed using electron paramagnetic resonance (EPR). For C₆₀ dimer 3, upon addition of 1 equivalent (BNA)₂ no electronic interaction in the C₆₀˙⁻–C₆₀˙⁻ was observed due to the long distance between the C₆₀ balls (20 Å). However, for C₆₀ dimer 1, where the distance between radicals is shorter, 10 Å, the electronic interaction in the di(radical anion), C₆₀˙⁻–C₆₀˙⁻ in the presence of 1 equivalent of (BNA)₂ was observed by EPR, corresponding to a triplet biradical.