Influence of Gallium Isomorphous Substitution in the Acidic MFI Zeolite Framework on Hole Formation, Transfer, and Trapping upon Incorporation of Anthracene

The redox behavior of ACENE-3 upon sorption within the channels of Bronsted acidic H-GaZSM-5 is followed by using diffuse reflectance UV−vis−NIR spectrometry in parallel with continuous wave EPR techniques and with Raman spectrometry. Partial spontaneous ionization is clearly observed, whereas proton transfer does not occur. The intense internal proton electrostatic field, as well as the confinement effect on the occluded molecule, are put forward to explain charge separation and the long-lived ACENE-3•+ radical cation. The compartmentalization of ACENE-3•+ and trapped electron within H-GaZSM-5 hinders charge recombination but promotes hole transfer to the inner surface of the 10-membered ring (10-MR) channel. Pulsed X-band EPR experiments using the 2D-HYSCORE sequence were carried out to investigate the structural surrounding of unpaired electrons. The observation of electron couplings with 1H, 29Si, 69Ga, and 71Ga nuclei allows clear differentiation between the two successive charge separated states. Th...