Excited-state interactions in pyrrolidinofullerenes

Abstract

Two new pyrrolidinofullerenes, 1 and 2, have been synthesized, and their photophysical properties have been investigated. The pyrrolidinofullerene 1 has three phenyl groups attached to the 1, 2, and 5 positions of the pyrrolidine ring. The pyrrolidinofullerene 2, on the other hand, has a flexible attachment with an N-methylaniline end group and is the prototype of a fullerene-aniline dyad. Singlet and triplet excited-state properties of these two functionalized fullerene derivatives have been examined with picosecond and nanosecond laser flash photolysis. The singlet and triplet excited states of these fullerenes exhibit characteristic absorption bands in the vis-IR region of the spectrum. The functionalization of C₆₀ with pyrrolidine groups shift the excited-state absorption maxima to the blue. Three different quenchers, O₂, TEMPO, and ferrocene, are employed to investigate the reactivity of triplet excited states. The bimolecular quenching rate constants determined for these quenchers were in the range of 5.3 × 10⁸ to 7.7 × 10⁹ M^-1 s^-1. The excited-state interactions of these functionalized fullerenes are compared to that of C₆₀.