Synthesis and photophysical properties of ruthenocene-[60]fullerene dyads

Two novel ruthenocene-C60 dyads, with a 2-pyrazoline ring or a pyrrolidine ring as a linker, have been synthesized with the aim of providing a simple model of natural photosynthesis. The photophysical properties of the two ruthenocene-C60 dyads have been investigated by steady-state absorption and fluorescence, time-resolved fluorescence and nanosecond transient measurements in polar and non-polar solvents. The charge separation takes place in the ruthenocene-pyrazolino[60]fullerene more efficiently than in the ruthenocene-pyrrolidino[60]fullerene dyad. The lifetimes of the charge-separated states of the ruthenocene-pyrazolino[60]fullerene and the ruthenocene-pyrrolidino[60]fullerene dyads are 100 ns in PhCN. It was found that the ruthenocene-[60]fullerenes have an ability to prolong the charge-separated states compared with those for ferrocene-[60]fullerenes.