Clusters of bis- and tris-fullerenes

Abstract

Bis- and tris-fullerene derivatives [bis-(C₆₀) and tris-(C₆₀)] form suspendable clusters in mixed solvents (80% acetonitrile and 20% toluene). These clusters are optically transparent and exhibit interesting nanostructures with sizes ranging from 100 nm to 1 µm and shapes varying from elongated wires to entangled spheres. Ground- and excited-state properties of the clusters of the mono-, bis-, and tris-fullerene derivatives are compared with the corresponding properties of their monomeric forms through steady-state and time-resolved transient absorption spectroscopy. The singlet excited-state quenching of bis- and tris-fullerene derivatives by N-methylphenothiazine (NMP) occurs with rate constants of 5.5 × 10⁹ and 5.3 × 10⁹ M^-1 s^-1, respectively. The charge separation in these clustered fullerene derivatives is probed by monitoring the formation and decay of the C₆₀ radical anion and the radical cation of NMP. An increase in the number of fullerene moieties in the molecule helps in the formation of ordered cluster aggregates and this has a beneficial effect in stabilizing the electron-transfer products.