Photochemical reduction of C60 derivatives in aqueous systems containing titanium dioxide or ascorbic acid (EPR study)

The photoinduced electron transfer to water-soluble mono-adducts and various bis-functionalized C60 derivatives I–VI (see Scheme 1 in the text) were investigated by EPR spectroscopy in heterogeneous water/2-propanol TiO2 system, and also in aqueous solutions containing l-ascorbic acid as an electron donating substrate. Irradiated TiO2 suspensions of C60C(COONa)2/γ-CD and C60(C4H10N+)/γ-CD yielded an EPR signal A, characterized by gA=2.0000 and peak-to-peak width, ppA=0.095 mT, assigned to the fullerenesʹ mono-anion. The latter transforms with continuing irradiation into radicals B and C (gB=2.0005, gC=2.0009). In contrast, the three water-soluble anionic bis-adducts (IV–VI) gave rise to only a single narrow mono-anion EPR line M (ppM<0.02 mT) positioned at gM=2.0007.