On the efficiency of the photosensitized production of singlet oxygen in water suspensions of a tris(bipyridyl)ruthenium(II) complex covalently bound to an insoluble hydrophilic polymer

Abstract

It is shown that molecular oxygen in D2O is efficient in deactivating the lowest excited state of an insoluble hydrophilic polymeric equivalent of [Ru(bpy)3]2+(see structure 1). The rate constant for quenching by molecular oxygen of the lowest excited triplet charge transfer state of 1 in D2O saturated gel is found to be 4.4±0.5×108M-1s-1. Singlet molecular oxygen, which is characterized by its emission at 1270nm, is generated during quenching and decays with a lifetime of 18±3μs. The lifetimes for the decay of singlet oxygen, when it is generated by exciting D2O-solved sensitizers in the presence and absence of the unfunctionalized polymeric skeleton in the form of a D2O saturated gel, are 34±3 and 63±5μs, respectively. These shorter lifetimes for singlet oxygen in the polymeric gels are consistent with quenching of singlet oxygen by the hydroxyl groups present in the polymer. © 2001 Elsevier Science B.V.