Manipulating Excited State Properties of Iridium Phenylpyridine Complexes with "Push-Pull" Substituents.

We have prepared a series of complexes of the type [Ir III (ppy) 2 (L] n + complexes ( 1-4 ), where ppy is a substituted 2-phenylpyridine and L is a chelating phosphine thioether ligand. The parent complex ( 1 ) comprises an unsubstituted phenylpyridine ligand, whereas complex 2 contains a nitro substituent on the pyridine ring, complex 3 features a diphenylamine group on the phenyl ring, and 4 has both nitro and diphenylamine groups. Crystallographic, 1 H NMR, and elemental analysis data are consistent with each of the chemical formulae. DFT (density functional theory) computational results show a complicated electronic structure with contributions from Ir, ppy, and the PS ligand. Ultrafast pump-probe data show strong contributions from the phenylpyridine moieties as well as strong panchromatic excited state absorption transitions. The data show that nitro and/or diphenylamine substituents dominate the spectroscopy of this series of compounds.