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Incorporation of Anthracene into Zeolites: Confinement Effect on the Recombination Rate of Photoinduced Radical Cation‐Electron Pair
Author(s) -
Marquis Séverine,
Moissette Alain,
Brémard Claude
Publication year - 2006
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200600082
Subject(s) - chemistry , analytical chemistry (journal) , radical ion , electron paramagnetic resonance , anthracene , raman spectroscopy , photochemistry , photoionization , ion , ionization , nuclear magnetic resonance , organic chemistry , physics , optics
10.1002/cphc.200600082.abs 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 M n ZSM‐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@M n ZSM‐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 +