Synthesis of fullerohelicates and fine tuning of the photoinduced processes by changing the number of addends on the fullerene subunits

Two fullerene-substituted m-phenylene-bis-phenanthroline ligands have been prepared. The synthesis of the first derivative () is based on an esterification reaction between a Cs symmetrical cis-2 fullerene bis-adduct bearing a carboxylic acid function and a bis-phenanthroline alcohol (). The second ligand () has been obtained by reaction of a bis-phenanthroline malonate () and C60 under Bingel conditions. The copper(I) complexes of and have been prepared by treatment with a slight excess of Cu(CH3CN)4BF4. NMR spectroscopy and mass spectrometry analysis have unambiguously shown that these complexes are bis-copper(I) helicates substituted with two fullerene moieties. The photophysical properties of the copper(I) complexes and have been investigated. In both systems photoinduced electron transfer from the central metal-complexed unit to the external fullerenes may occur, in principle, by excitation of both moieties. However, this is found to be the case only for the methanofullerene system . Unexpectedly, for , photoexcitation of the peripheral carbon spheres is followed by regular internal deactivation. Possible reasons for this behavior are examined in light of current theories for photoinduced energy and electron transfer.