Tuning the emission of cyclometalated iridium complexes by simple ligand modification

The photo-excitation and relaxation of a new cyclometalated complex, Ir(ppy)(2)fppy, is investigated through the measurement of absorption and photoluminescence spectra. Comparison of Ir(ppy)(2)fppy with Ir(ppy)(3) reveals that the lowest energy excited state of Ir(ppy)(2)fppy is localised on the aldehyde-substituted ligand, thus giving the complex its characteristic orange emission (lambda(max) approximate to 600 nm). OLEDs containing Ir(ppy)(2)fppy doped into poly(vinylcarbazole) (PVK) exhibit the same characteristic emission as found in solution, implying efficient energy transfer between the PVK and the iridium complex. Our results provide the potential for the synthesis of iridium complexes with different emission wavelengths through the modification of only one ligand.