Magnetic field effects on the decay rates of triplet biradical photogenerated from intramolecular electron-transfer in a zinc-tetraphenylporphyrin-fullerene linked compound

Transient absorption spectra of a zinc-tetraphenylporphyrin(ZnP)-fullerene(C60) linked compound with flexible eight methylene groups indicated that intramolecular electron-transfer occurred in benzonitrile, while not in toluene. In benzonitrile, the decay rate constant of biradical decreases quickly in lower magnetic fields (<0.1 T), and then increases gradually and finally become almost constant in higher magnetic fields (0.1⩽H⩽1.2 T). The magnetic field effects (MFEs) verified that the triplet biradical was generated from the intramolecular electron-transfer of the triplet-excited states of ZnP and C60. The reverse phenomenon of the MFEs around 0.1 T is most likely ascribed to the properties of C60 moiety.