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 C-60 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)/gamma-CD and C-60(C4H10N+)/gamma-CD yielded an EPR signal A, characterized by g(A) = 2.0000 and peak-to-peak width, pp(A) = 0.095 mT, assigned to the fullerenes' mono-anion. The latter transforms with continuing irradiation into radicals B and C (g(B) = 2.0005, g(C) = 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 (pp(M) < 0.02 mT) positioned at g(M) = 2.0007. (C) 1999 Elsevier Science B.V. All rights reserved.