Photophysical properties of iridium complexes containing diamine ancillary ligands in the presence of phenylpyridine as cyclometalated ligand

A set of iridium complexes of [Ir(ppy)2(amino-containing ligand)]PF6, where diamino-containing ligand = 1,2-diaminobenzene (1), 4-nitro-1,2-diaminobenzene (2), 4-methoxy-1,2-diaminobenzene (3), N,N’-dimethyl-1,2-diaminobenzene (4), N-methyl-1,2-diaminobenzene (5), and N-phenyl-1,2-diaminobenzene (6) were synthesised and characterised by high-resolution mass spectrometry as well as 1H, 13C, 31P, and 19F NMR spectroscopy. In this study, 2,2′-bpy is replaced with a lower electron donating ligands, leading to a high lowest unoccupied molecular orbital (LUMO) energy. All the complexes show a blue shifted emission compared to the archetypal iridium complex [Ir(ppy)2bpy]PF6 with different emission nature, resulting in different photophysical properties. Density functional theory shows a weak metal-ligand interactions indicated by the elongation of the bond distance between the Ir and the ancillary ligands.