Multicomponent donor-acceptor relay system assembled within the cavities of zeolite Y.: Photoinduced electron transfer between Ru(bPY)32+ 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 (lambda(ex) = 466 nm, lambda(em) = 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, (similar to50 nm) act mainly as insulators between good electron donor and acceptor molecules as opposed to electron relays.