π-Dimerization of viologen subunits around the core of C60 from twelve to six directions

Abstract

Molecular reorganization around the core of C₆₀ has been achieved by electron transfer centered on π-dimerizable viologen subunits located in a restricted region of space. Fullerene C₆₀ hexaadducts, featuring 12 viologen subunits, have been prepared by using copper-mediated Huisgen 1,3-dipolar cycloaddition of azides with alkynes. Detailed electrochemical studies, supported by UV-Vis and EPR spectroscopic analyses, demonstrate that the linkers bearing the viologen subunits attached to specific positions around the all-carbon sphere, allow the formation of six intramolecular π-dimers. Theoretical calculations reveal that the close proximity of the orbitals of the viologen subunits attached to the C₆₀ facilitate the π-dimerization of the bis-radical species. These investigations support the fact that the motion of discrete peripheral groups oriented around the all-carbon sphere of C₆₀ can be controlled electrochemically using noncovalent reversible interactions.