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

摘要

It is shown that molecular oxygen in D_2O 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 D_2O saturated gel is found to be 4.4±0.5 * 10~8 M~(-1) s~(-1). Singlet molecular oxygen, which is characterized by its emission at 1270 nm, is generated during quenching and decays with a lifetime of 18±3 μs. The lifetimes for the decay of singlet oxygen, when it is generated by exciting D_2O-solved sensitizers in the presence and absence of the unfunctionalized polymeric skeleton in the form of a D_2O saturated gel, are 34±3 and 63±5 μs, 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.