Radical Anions of Fullerene Bisadducts: A Multifrequency CW-EPR study.

The radical anions of three C60 bisadducts (from now on termed CIS1, CIS2, and CIS3) have been studied in liquid solution and glassy matrix by X-band and high frequency CW-EPR spectroscopy. The three adducts CIS1, CIS2, and CIS3 are characterized by a pyrrolidinic ring and an isoxazolinic ring in position cis1-O, cis2-C, and cis3-C, respectively; the two rings are connected by a methylenic chain. In the X-band spectra of CIS1, one species has been observed showing hyperfine coupling constants with the pyrrolidinic nitrogen and nuclei, whereas in the X-band spectra of CIS2 and CIS3 more species are apparent, some with and other without hyperfine coupling with the pyrrolidinic . High field spectra at 110 and 220 GHz for all the bisadducts have been obtained; in all the cases, more species are evident with small differences in the g-factors. The occurrence of more species are discussed and put in relation with different bisadduct conformations. Furthermore, on the basis of the mechanism proposed for the hcc in previously studied fulleropyrrolidine (FP) monoanions, the presence or absence of hcc for CIS1 and the different conformations of CIS2 and CIS3 is discussed. The temperature dependence of the EPR linewidths and the g-factors of all the species have been determined and discussed in term of the different structural stiffness and symmetry of the three bisadducts.