Molecular Crystals and Liquid Crystals, Vol.444, 145-155, 2006
Synthesis and photophysical studies of iridium complexes of fluorinated phenylisoquinolines
There have been reported materials emitting green color in both fluorescence and phosphorescence with great success, however efficient red luminescence materials are rare. Recently, it has been reported iridium (III) complexes of 1-(phenyl)isoquinoline (piq) and 1-(4'-fluorophenyl) isoquinoline (piq-F) show strong electroluminescence (EL) brightness and efficiency, even at high currents. These complexes show the strong intensity of band around 450 nm assigned to the spin-forbidden (MLCT)-M-3 (metal to ligand charge transfer) transition . In this study, Ir(III) complexes of fluorinated piqs (piq-F , piq-2F, piq-CF3) as cyclometalated ligand were prepared and photonic properties were investigated to improve the EL efficiency. The Ir(III) complex with piq-CF3 ligands exhibits the largest emission efficiency with maximum at 612 nm. The result of ab. Initio calculation using the Time-dependent density functional theory (TD-DFT) shows that the strong (MLCT)-M-3 transition of the complex is due to the strong coupling between the 5d orbital of the Ir atom and the highest occupied molecular orbitals (HOMOs) of ligands.