Transient absorption spectra of a fullerene (C-60)-phenothiazine (PH) linked compound indicated that the intramolecular electron transfer occurred in benzonitrile, while not in benzene. In benzonitrile, the lifetime (118 ns) of photogenerated biradical was very long, in spite of being around the top region in Marcus theory. The lifetime of the biradical was enhanced by 1.8 times in the presence of magnetic fields (>0.2 T). The magnetic field effects verified that the triplet biradical was generated from the intramolecular electron transfer from PH to the triplet C-60. The long lifetime is most likely ascribed to spin multiplicities of the biradical.