Magnetic field effects (MFEs) and time-resolved EPR on photogenerated biradical from intramolecular electron-transfer reactions in zinc-tetraphenylporphyrin (ZnP)-C 60 linked compounds (ZnP(4)C 60 and ZnP(8)C 60 ) with flexible four and eight methylene groups have been investigated in benzonitrile. At low temperature (288K), the decay rate constant of the biradical decreased steeply in low magnetic fields (0.1 ≤ H ≤ 0.6 T) and finally became almost constant in high magnetic fields (0.6 ≤ H ≤ 1T) in both ZnP(4)C60 and ZnP(8)C60. At high temperature (323 K), in contrast, the decay rate constant decreased slightly in low magnetic fields (<0.1 T), and then increased gradually in higher magnetic fields (0.1 ≤ H ≤ 1 T). Interestingly, the decay rate constants in higher magnetic fields (0.4 ≤ H ≤ 1 T) were larger than that in zero magnetic field. The reverse phenomena of the MFEs around 0.1T and temperature dependence on the MFEs are explained by the contribution of spin-spin relaxation due to anisotropic Zeeman interaction to the relaxation mechanism and most likely ascribed to the properties of C60 anion radical due to the spherical π-system. The mechanism is also supported by the time-resolved EPR spectra.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Condensed Matter Physics
- Physical and Theoretical Chemistry