Fullerenes: three dimensional electron acceptor materials

This feature article highlights the advantages of employing [60]fullerene as a viable electron accepting building block in novel donor acceptor systems. Different strategies that aim towards improving charge separation in fullerene containing systems are presented. This is accomplished, for example, via utilisation of additional stabilisation forces of the radical pair or, alternatively, diffusional splitting of the last mentioned. Fine-tuning the topology of the electron donor moiety has been shown to be a powerful means of influencing the relative energies of the two states involved (e.g. the charge-separated state vs. the singlet ground state). Remarkable effects concerning the lifetime of the charge-separated radical pair were observed, in particular, in systems that upon charge separation led to a gain of aromaticity and planarity of the oxidised fragment.