Unusual Terpyridines as Ligands for Novel Light-Emitting Iridium(iii) Complexes: Synthesis and Characterization

Based on S-shaped terpyridines, a series of yellow, orange, and red-orange light-emitting iridium(iii) complexes has been synthesized. The respective compounds have been prepared by the bridge-splitting method starting from the dimeric precursor complexes [(ppy)2Ir-µ-Cl]2, [(ppy-CHO)2Ir-µ-Cl]2, and [(c6)2Ir-µ-Cl]2. The products have been fully characterized by one- and two-dimensional (1H–1H correlation) NMR spectroscopy, elemental analysis, and MALDI-TOF mass spectrometry revealing the successful coordination of the iridium(iii) centres to the S-shaped terpyridine ligands. Furthermore, the quantitative coordination has been verified by the photophysical and electrochemical properties of the mononuclear iridium(iii) complexes. The photoluminescence spectra have shown strong emissions with maxima between 538 and 600 nm. The study of the optical properties of these novel complexes has indicated that the colour shifts are mainly depending on the nature of the cyclometallating ligands.