UV-irradiation of a toluene solution Of C60Ph5Cl leads to the formation of the stable C60Ph5 cyclopentadienyl-type fullerenyl radical. Under UV-irradiation of a toluene solution of C60Ph5Cl containing Hg[P(O)(OPr')(2)](2) (Pr-i= CH(CH3)(2)), three isomers of the adducts of phosphoryl radicals with C60Ph5Cl are formed. Density functional (DFT) approach with the B3LYP functional was used for estimating of the enthalpies of the formation and hyperfine coupling constants for all possible adducts of phosphoryl radicals with C60Ph5Cl. Biradical particles C60Ph5[P(O)(OPri)(2)]-(C60Ph5)-C-.[P(O)(OPri)(2)] with a distance between impaired electrons of about 10.5 Angstrom, are also obtained. (C) 2003 Published by Elsevier B.V.