Luminescent NCN cyclometalated iridium(III) acetylide complexes with fluorene and carbazole motifs

Highlights: • Iridium acetylide complexes with fluorene and carbazole motifs were examined. • Detailed characterization of optical, thermal and electrochemical properties of new complexes has been carried out. • In the Ir(III) complexes the emission takes place from the mixed state ³MLCT/³LC. -- Abstract: NCN cyclometalated iridium(III) acetylide complexes in the 3 + 2+1 ligand mode were obtained and characterized. Cyclometalating ligands were bis(pyridyl)phenyl, bis(benzothiazolyl)phenyl and 2-phenylpyridine derivatives, while acetylene ligands represented 2-ethynylfluorene and 3-ethynylcarbazole derivatives. The HOMOs of the ethynyl iridium complexes are located on the ethynyl ligand and the iridium atom, whereas the LUMO is located exclusively on the NCN-cyclometalating ligand. All compounds showed phosphorescent properties, where the change of ligands significantly affects the wavelength of emission. Acetylide complexes emit light from the blue (∼ 400 nm) to orange (∼ 560 nm) range. Emission occurs from the mixed state ³MLCT/³LC, with a predominance of junction depending on the structure of the ligands.