Aryl 5-substitution of a phenyl-pyridine based ligand as a viable way to influence the opto-electronic properties of bis-cyclometalated Ir(III) heteroleptic complexes.

This manuscript reports on the synthesis, the photophysical study and the electroluminescent properties of a series of heteroleptic cyclometalated iridium(III) complexes based on 2,5-diaryl-pyridines as C^N cyclometalating ligands and acetylacetonate as ancillary ligand. The complexes were characterised by elemental analysis, ESI-MS, multinuclear NMR, TGA and electrochemistry. Their optical properties were investigated by UV-Vis and photoluminescence. DFT and TD-DFT calculations provided further insights into the effects of the 5-aryl substitution on the electronic and photophysical properties of the new complexes. The presence of suitable π-extended ligands exerts a beneficial effect on the performances of the corresponding solution-processed light-emitting diodes, leading to a maximum brightness of 10,620 cd m(-2) at a current efficiency of 10.0 cd A(-1).