title: Effects of spatial constraints and Brønsted acid site locations on para-terphenyl ionization and charge transfer in zeolites.
abstract: The locations of Brønsted acid sites (BAS) in the channels of medium-pore zeolites have a significant effect on the spontaneous ionization of para-terphenyl (PP(3)) insofar as spatial constraints determine the stability of transition states and charge-transfer complexes relevant to charge separation. The ionization rates and ionization yield values demonstrate that a strong synergy exists between the H(+) polarization energy and spatial constraints imposed by the channel topology. Spectroscopic and modeling results show that PP(3) incorporation, charge separation, charge transfer and charge recombination differ dramatically among zeolites with respect to channel structure (H-FER, H-MFI, H-MOR) and BAS density in the channel. Compartmentalization of ejected electrons away from the initial site of ionization decreases dramatically the propensity for charge recombination. The main mode of PP(3)(.+) decay is hole transfer to form AlO(4)H(.+) ⋅⋅⋅PP(3) charge-transfer complexes characterized by intense absorption in the visible range. According to the nonadiabatic electron-transfer theory, the small reorganization energy in constrained channels explains the slow hole-transfer rate.
authors: Laboratoire de Spectrochimie Infrarouge et Raman UMR-CNRS 8516, Centre d' Etudes et de Recherches Lasers et Applications, FR-CNRS 2416, Bât. C5 Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq cedex, France.
authors: Fatima
authors: F
authors: Belhadj
authors: Alain
authors: A
authors: Moissette
authors: Claude
authors: C
authors: Brémard
authors: Matthieu
authors: M
authors: Hureau
authors: Zoubir
authors: Z
authors: Derriche