Temperature dependence on magnetic field effects on the decay rates of triplet biradical photogenerated from intramolecular electron-transfer in a phenothiazine-C60 linked compound

The decay rate constants of the photogenerated biradical of a phenothiazine-C60 linked compound dramatically decreased in lower magnetic fields (0–0.2 T) and then gradually increased in higher magnetic fields (0.2–1 T) in benzonitrile at various temperatures (283–343 K). As temperature increased, the magnitudes of magnetic field effects (MFEs) in the lower magnetic fields were reduced, while those in the higher magnetic fields were enhanced. These reverse phenomena in the MFEs are explained by the contribution of spin-lattice relaxation mechanism due to anisotropic Zeeman interaction. The temperature effect supports the above mechanism and is probably ascribed to the molecular motion in the biradical.