Incorporation of anthracene into zeolites : confinement effect on the recombination rate of photoinduced radical cation-electron pair

S. Marquis (1, 2) , A. Moissette (1, 2) , C. Brémard (1, 2)

1 LASIRE - Laboratoire Avancé de Spectroscopie pour les Intéractions la Réactivité et l'Environnement - UMR 8516
2 CERLA - Centre d'Etudes et de Recherches Lasers et Applications

FT-Raman spectrometry in combination with diffuse reflectance UV/Vis absorption (DRUVv) and fluorescence emission indicate that complete anthracene (ANT) sorption as intact molecules takes place over 6 months in the medium pores of non-Brønsted acidic MnZSM-5 zeolites (n=0.0, 3.4, 6.6; M=Na+, K+, Rb+, Cs+) with 1 ANT per unit cell loading. The combined effect of confinement and electrostatic field induced by bulky cations (Rb+, Cs+) leads to specific changes in the occluded ANT Raman spectra after very long organization periods (one year). The laser photolysis (266 nm, 355 nm) of ANT@MnZSM-5 equilibrated samples generates long-lived charge separated species in aluminum rich zeolites (n=3.4, 6.6). The very long-lived radical pairs are characterized by conventional DRUVv and CW-EPR spectroscopy. The direct charge recombination rates of ANT.+-electron pairs are dispersive, extending over a broad range of timescales. The kinetic constant values are found to increase dramatically with the aluminum content and increase markedly with M+ according to the following order Na+

S. Marquis, A. Moissette, C. Brémard. Incorporation of anthracene into zeolites : confinement effect on the recombination rate of photoinduced radical cation-electron pair. ChemPhysChem, 2006, 7, pp.1525-1534. ⟨10.1002/cphc.200600082⟩. ⟨hal-00268056⟩