Effect of ligands in two-photon excited luminescence of organometallic iridium complexes

We studied the effect of ligand modification on the excited-state lifetime of the phosphorescent organometallic complex Ir(ppy)3. Modification of one of the phenylpyridine ligands with an aldehyde group causes localization of the excitation on the modified ligand and a large red shift of the phosphorescence spectra. On the other hand, the modification does not affect the appearance of a two-photon-excited fast (ns) luminescence component, the intensity of which increases with decreasing concentration of the complex in solid poly(methyl methacrylate) (PMMA) film.