Synthesis of starburst hexa(oligoanilinated) C60 using hexanitro[60]fullerene as a precursor

Abstract

Efficient syntheses of starburst hexaanilino, hexa(dianilino), hexa(tetraanilino), and hexa(hexadecaanilino)[60]fullerenes (HHDAF) were demonstrated using hexanitro[60]fullerene (HNF) as a reactive precursor molecule. The tertiary nitro groups of HNF were found to act as excellent leaving groups for replacement by a nucleophilic substituent. Utilizing this reactivity with electron-donor nucleophiles, a synthetic approach was developed for the production of oligoanilinated fullerenes as intramolecular donor–acceptor A–(D)₆ starburst macromolecules with a well-defined arm number and chain length. The reactivity of HNF with oligomeric anilines increases with increasing number of repeating aniline units. Only an equal molar quantity of tetraaniline and hexadecaaniline was necessary for a complete reaction with HNF under mild conditions. The quantitative measurement of the material’s proton counts over the ¹H NMR spectrum was utilized for determining the number of addends per C₆₀ in the composition of oligoanilinated fullerenes. As a result, the NMR data fits well with the structure of tetraanilinated and hexadecaanilinated fullerenes, containing 6 tetraanilino and hexadecaanilino arms per C₆₀, respectively. This composition of HHDAF was also supported by the DCI^–-MS spectroscopic data showing an approximate correlation of the total relative peak intensities of fragmented oligoanilino mass ion groups. The optical properties of hexa(hexadecaanilino)[60]fullerenes revealed a close similarity with that of high molecular weight polyanilines.