Clusters of bis- and tris-fullerenes

Bis- and tris-fullerene derivatives [bis-(C-60) and tris-(C-60)] 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 mum 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 x 10(9) and 5.3 x 10(9) M-1 s(-1), respectively. The charge separation in these clustered- fullerene derivatives is probed by monitoring the formation and decay of the C-60 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 duster aggregates and this has a beneficial effect in stabilizing the electron-transfer products.