Defect Emission from LPPPs

The PL emission from 71 is very similar to that from 66 with maxima at 460 and 490 nm. However, the EL spectrum shows an additional long-wavelength band. This is not a broad featureless band as seen for the defect emission from 3 or 66, but one with well-resolved maxima at 600 and 650 nm. Photophysical investigation of this emission showed the feature at 600 nm to be emission from a triplet exciton (phosphorescence) with a vibronic shoulder at 650 nm [150]. Elemental analysis of the polymer showed that it contained 80 ppm of palladium (cf. 2 ppm in 66). It was therefore proposed that residues of the palladium catalyst used to make the precursor polymer 59 reacted with the phenyl lithium and the polymer to introduce covalently bound palladium centres onto the polymer chain. These then act as sites for phosphorescent emission. 

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