Excited-state equilibration in a meso-/microporous material-hosted bichromophoric [Ruthenium (2,2′-bipyridine)3]: Reversible energy transfer and photosensitized electron pumping

A bichromophoric pyrene-appended [Ru(bpy)₃]²⁺-type complex (bpy = 2,2′-bipyridine) showing rapid, reversible intramolecular energy transfer processes leading to an excited-state equilibration in homogeneous solutions was introduced into different photoinert supports, namely MCM-41, ethylene-bridged periodic mesoporous organosilica (PMO), and zeolite NaY. Its photophysical behaviour in each of these supports is compared with its behaviour in solution and with that of an appropriate model lacking the pyrene chromophore, [Ru(bpy)₂dmb]²⁺. Results suggest that the excited-state equilibration process which is operational in homogeneous solutions leading to long-luminescence lifetimes, is equally observed in all the different supports. A diminished oxygen sensitivity and prolonged luminescence lifetime was recorded for all the complexes included with respect to the analogous species in solution. The adsorbed pyrene-appended [Ru(bpy)₃]²⁺ complex is also shown to participate in photosensitized electron pumping from zeolite NaY to a size-excluded methylviologen in solution more efficiently than the adsorbed parent complex.