The efficient blue photoluminescence of pyrazolo-[3,4-b]-quinoline derivatives and the energy transfer in polymer matrices

The photophysical properties of a series of pyrazolo-[3,4-b]-quinoline derivatives have been studied in solution and as dopants in several polymer matrices (polycarbonate (PC), polystyrene (PS), poly(methyl methacrylate) (PMMA) and poly(N-vinyl carbazole) (PVK)). In solution these materials exhibit a high quantum yield for fluorescence at 450 nm of between 76% and 100%. The variation in substitution of the pyrazoloquinoline core of this series of materials has little effect on the photophysical properties in solution or in the polymer films. The materials exhibit little concentration quenching as the photoluminescence efficiencies remain high even at high dopant concentration. However, there is significant interaction of the dopant with the polymer matrices causing modification of the dopant absorption and excitation spectra and faster fluorescence decays. In the case of the PVK matrix there is evidence for the existence of a rapid energy transfer pathway from the polymer to the dopant. The results show that pyrazoloquinolines are a promising class of materials for use in optical and optoelectronic applications. (C) 2000 Elsevier Science B.V. All rights reserved.