Energy Transfer from Luminescent Porous Silicon to Adsorbed Osmium(II) and Ruthenium(II) Polypyridyl Complexes

摘要

Surface adsorption of transition-metal polypyridyl complexes on highly luminescent, anodized porous silicon (p-Si) wafers leads to dramatic quenching of the emission. Facile energy transfer occurs from the surface to adsorbed complexes of Run and Os250L?Ⅱ). Photoluminescence (PL) from underivatized p-Si is excitation- and monitoring-wavelength-dependent. A phenomenological model is proposed to explain these observations in which intercluster energy transfer occurs by an energy-transfer cascade, and there is weak kinetic coupling to even lower-energy surface emitters. Adsorption of [Zn(dmb)↓(3)](PF↓(6))↓(2) (dmb is 4,4'-dimethyl-2,2'-bipyridine) or fac-[Re(bpy)(CO)↓(3)(4-Etpy)](PF↓(6))↓(2) (bpy is 2,2'-bipyridine; 4-Etpy is 4-ethylpyridine), possibly by ion-exchange, results in quenching of the low-energy surface emitters. For adsorbed [Ma(bpy)↓(2)(4-CO↓(2)H-4'Mebpy)]-(PF6)2 (M = Ru, Os; 4-CO2H-4'Mebpy is 4-carboxylic acid-4'-methyl-2,2'-bipyridine), p-Si → MⅡ energy transfer occurs to low-lying metal-to-ligand charge-transfer (MLCT) excited states on the complexes as revealed by excitation and emission measurements. Energy transfer is efficient (>90%) and more rapid for OS↑(Ⅱ) (ken≈6 × 106 s↑(-1)) than for Run by a factor of ~10, consistent with a decrease in driving force for p-S→ M↑(Ⅱ)energy transfer.