Deep-Red Phosphorescent Iridium(III) Complexes with Chromophoric N-Heterocyclic Carbene Ligands: Design, Photophysical Properties, and DFT Calculations

The synthesis of three deep-red-emitting iridium(III) complexes featuring a naphthalimide N-heterocyclic carbene ligand was investigated. The introduction of this organic chromophore onto the carbene moiety changed the character of the lowest excited state from triplet metal-to-ligand charge transfer to triplet ligand centered, as corroborated by time-dependent DFT calculations. All complexes displayed a naphthalimide- based deep-red phosphorescence emission above lambda = 630 nm in polymer matrix with good quantum yields (Phi approximate to 0.2) and long lifetimes.