Fullerene Complex with Tetrathiafulvalene-Type Donors

Significance

A threefold Wittig-Horner olefination reaction of truxenone 1 with the carbanion generated in situ from the corresponding phosphonate esters 2-4 in the presence of n-BuLi provided truxene-tetrathiafulvalene (TTF) compounds 5-7 in 42-67% yields. X-ray crystallography study of 5 showed that the concave bowl-shaped configuration adopted by the truxene core perfectly mirrors the convex surface of fullerenes. The association of 5 and fullerenes in solution was investigated by ¹H NMR titrations of 5 as host with C₆₀ and C₇₀ as guests, which afforded binding constants of (1.2 0.3) 10³ M^-1 and (8.0 1.5) 10³ M^-1 for C₆₀ and C₇₀, respectively. Theoretical calculations also indicate that C₇₀ interacts with 5 more effectively than C₆₀, leading to slightly more stable complexes.