Multicomponent Donor−Acceptor Relay System Assembled within the Cavities of Zeolite Y. Photoinduced Electron Transfer between Ru(bpy)3 2+ and 2,4,6-Triphenylpyrylium in the Presence of Interposed TiO2

Zeolite Y containing Ru(bpy)3 2+ and TP+ has been obtained by the stepwise ship-in-a-bottle synthesis of the two components. The identity of the two ions has been demonstrated by diffuse reflectance UV−vis and IR spectra. Emission spectra (λex = 466 nm, λem = 600 nm) corresponding to the Ru(bpy)3 2+ lumophore indicate that 70% of the Ru(bpy)3 2+ complexes interact with TP+ through static quenching; only a weak emission corresponding to the unquenched complex is observed. The transient absorption spectrum of [Ru(bpy)3 2+−TP+]@Y obtained by laser flash photolysis is complex, but the presence of Ru(bpy)3 3+ was detected. The co-incorporation of semiconductor oxide TiO2 disfavors the Ru(bpy)3 2+−TP+ interaction, restoring the Ru(bpy)3 2+ emission to 90% of the original value. This indicates that small TiO2 clusters of a few Ti atoms occupying the empty zeolite space (1.3 nm) and, having a much larger band gap than regular TiO2, (∼50 nm) act mainly as insulators between good electron donor and acceptor molecules as opposed to electron relays.