Mechanisms of Formation and Deactivation of Extremely Long-Lived Charge-Separated State following Photoinduced Electron Transfer in Carbazolyl Polymers Coadsorbed with 1,2,4,5-Tetracyanobenzene on Macroreticular Resins

At room temperature, extremely long-lived (>8 h) charge-separated (CS) states following photoinduced electron transfer were found for poly(N-vinylcarbazole) (PVCz) coadsorbed with 1,2,4,5-tetracyanobenzene as an electron acceptor on a macroreticular resin, Amberlite XAD-8. The formation of the long-lived CS states was ascribed to both a hole-migration process along the polymer chain and a hole-trapping process resulting in the large interionic distance. The temperature dependence on the decay profiles of the long-lived CS states indicated that the charge recombination due to the long-distance electron tunneling was responsible for the disappearance of the CS states in the long time region. The simulation curve taking account of both the long-distance electron transfer and the distribution of the interionic distance reproduced the decay profiles of the CS states fairly well. The effects of both tacticity of PVCz and the modification of the adsorbents on the formation and the deactivation processes of the long-lived CS states were examined. The results revealed that the deep hole-trap sites resulting in the large interionic distance were not simply related to the carbazolyl dimer cation sites but to the carbazolyl moieties adsorbed in the vicinity of the polar ester groups in the adsorbent.