ANALYSIS OF DELAYED LUMINESCENCE FROM SOME QUENCHERS OF TB(DPA)(3)(3-) EMISSION - PROOF FOR AN ENERGY-TRANSFER QUENCHING MECHANISM

The long-lived luminescence from Tb(DPA)(3)(3-) (DPA = pyridine-2,6-di carboxylate dianion) can be quenched by Rhodamine 6G, Rhodamine B, som e urobilin derivatives and Ru(phen)(3)(2+) (phen = 1, 10-phenanthrolin e). Using time-resolved emission spectroscopy we have studied these re actions. The observation of delayed luminescence from the quenchers co nstitutes direct evidence that electronic energy transfer is involved in the quenching process. Quantitative analysis of the delayed fluores cence and of the lanthanide emission, in conjunction with measurement of the luminescence quantum yield of Tb(DPA)(3)(3-) (phi = 0.7 +/- 0.1 5), shows that the production of the electronically excited quencher s tate in the quenching process occurs with nearly unit efficiency for a ll the quenchers studied. Additional experimental evidence is provided for the view that energy transfer takes place in encounter pairs wher e donor and acceptor are in close contact.