17 March 2000 Ž . Chemical Physics Letters 319 2000 309–317 www.elsevier.nlrlocatercplett Reactions of photoexcited C with weak organic acids. Novel 60 method for the derivatization of fullerenes M. Fedurco a, ) , K. Klostermann b , U. Kirbach c , D. Scheller d , L. Dunsch c a UniÕersity of GeneÕa, Department of Chemistry, 30 quai Ernest-Ansermet, CH-1211 GeneÕa, Switzerland b Technische UniÕersitat Dresden, Institut fur Analytische Chemie, D-01069 Dresden, Germany ¨ ¨ c IFW Dresden, Institut fur Festkorperforschung, Helmholtzstrasse 20, D-01171 Dresden, Germany ¨ ¨ d Technische UniÕersitat Dresden, Institut fur Organische und Farbenchemie, Mommsenstraße 13, D-01069 Dresden, Germany ¨ ¨ Received 26 November 1999; in final form 11 January 2000 Abstract Pyrex-filtered irradiation of C solutions in liquid diphenylmethane in the absence of oxygen is shown to result in 60 Ø Ž . Ph CH radicals, which further react with the electron-deficient C to give Ph CH–C H n s1, 3, 5 . The fullerene 2 60 2 60 n ground state to 3 C transition is suggested to be accompanied by the increase of the fullerene solvation affecting thus the 60 acidity of methylene hydrogens in Ph CH as well as the feasibility of their dissociation. Also, photolysis of C solutions 2 2 60 in weakly acidic phenylacetylene is shown to lead to the addition of a varying number of phenylethinyl groups to the fullerene core. q 2000 Elsevier Science B.V. All rights reserved. 1. Introduction Feasibility of multiple radical additions to fullerene in the presence of free radical species has w x been demonstrated in several studies in liquids 1–4 wx as well as in the gas phase 5 . A characteristic feature of such reactions is the addition of an unusu- ally large number of functional groups to the fullerene core. For example, either 15 benzyl groups, or at least 34 methyl groups, could be covalently attached to fullerene during irradiation of di-tert-butylpero- xide in toluene, depending on the reaction tempera- wx ture 6 . However, such reactions often lead to the addition of radicals formed from the irradiated or- ) Corresponding author. Fax: q 41-022-702-6029; e-mail: milan.fedurco@chiam.unige.ch Ž . ganic molecule target molecule as well as from the initiator of the radical reactions. A similar problem was encountered during the phenylation of C in the 60 Ž . presence of a Grignard reagent i.e., PhMgBr and w x methyl iodide 7,8 . The latter usually leads to ring- opening reactions and gives four different fullerene Ž . isomers diphenyl fulleroids and methanofullerenes w x 9,10 . The fact that diphenylmethyl radicals can indeed be generated from DPM and photoexcited BP molecules comes from a recent study reported by w x Saitow et al. 11 . These authors observed exciton- assisted hydrogen abstraction from diphenylmethane Ž doped in benzophenone crystal however, no such . studies have yet been reported in solution . Diphenylmethyl radicals formed upon UV irradiation of the crystal were stable in the solid state for more than two weeks. Surprisingly, we find that the pres- ence of benzophenone in liquid diphenylmethane is 0009-2614r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0009-2614 00 00049-X