Luminescence and energy transfer of [Ru(bpy)3]2+, [Cr(ox)3]3-, and [Os(bpy)3]2+ in three-dimensional oxalato-networks

Luminescence and energy transfer in [Zn1-xRux(bpy)(3)] [NaAl1-yCry(ox)(3)] (x approximate to 0.01, y = 0.006 - 0.22; bpy = 2,2'-bipyridine, ox = C2O42-) and [Zn1-x-yRuxOsy(bpy)(3)] [NaAl(ox)(3)] (x approximate to 0.01, y = 0.012) are presented and discussed. Surprisingly, the luminescence of the isolated luminophores [Ru(bpy)(3)](2+) and [Os(bpy)(3)](2+) in [Zn(bpy)(3)] [NaAl(ox)(3)] is hardly quenched at room temperature. Steady-state luminescence spectra and decay curves show that energy transfer occurs between [Ru(bpy)(3)](2+) and [Cr(ox)(3)](3-) and between [Ru(bpy)(3)](2+) and [Os(bpy)(3)](2+) in [Zn1-xRux(bpy)(3)] [NaAl1-yCry(ox)(3)] and [Zn1-x-yRuxOsy(bpy)(3)] [NaAl(ox)(3)], respectively; For a quantitative investigation of the energy transfer, a shell type model is developed, using a Monte Carlo procedure and the structural parameters of the systems. A good description of the experimental data is obtained assuming electric dipole-electric dipole interaction between donors and accepters, with a critical distance R-c for [Ru(bpy)(3)](2+) to [Cr(ox)(3)](3-) energy transfer of 15 Angstrom and for [Ru(bpy)(3)](2+) to [Os(bpy)(3)](2+) energy transfer of 33 Angstrom. These values are in good agreement with those derived using the Forster-Dexter theory.