Forster energy transfer from poly(arylene-ethynylene)s to an erbium-porphyrin complex

We study the infrared emission at 1.54 mum of an organolanthanide complex, Er(III)-tetraphenylporphyrin [Er(TPP)acac], both as a result of direct optical excitation and via energy transfer from host pi-conjugate polymers of type poly(arylene-ethynylene) [PAE]. In the first case, the emission of the neat complex is characterized in inert transparent materials and a value of the quantum yield at 1.54 mum phi(IR) = 4 x 10(-4) is measured. Then, fluorescence resonance transfer is investigated in blends of Er(TPP)acae with PAEs by monitoring the quenching of the polymer fluorescence along with the enhancement of both the visible emission of the ligand and the near-infrared band of Er3+. These different procedures allow a detailed analysis of the transfer efficiency within a specific implementation of the Forster model for polymeric donors. The experimental values of the critical radius R-0, ranging from 1.3 to 2.5 nm for the different blends, are in good agreement with theory for a wide interval of the physical and spectroscopic parameters. This suggests that other mechanisms for excitation transfer do not play a significant role in these materials. (C) 2004 Elsevier B.V. All rights reserved.