Electronic Structures and Spectroscopic Properties of a Novel Iridium (Ⅲ) Complex with an Ancillary Ligand 2-(4-Trifluoromethyl -2-Hydroxylphenyl)Benzothiazole

Iridium(Ⅲ)complexes with 2−phenylpyridine(ppy)have been demonstrated as a type of promising phosphorescence dopant in emitting layers of organic light emitting diodes(OLEDs).In most iridium(III)complexes,there exist the strong spin−orbit coupling betweenπ−orbitals of cyclometalated ligands and 5d orbitals of the centric iridium.We study a novel iridium(Ⅲ)complex(ppy)2Ir(4−TfmBTZ)with ppy as cyclometalated ligands and 2-(4-trifluoromethyl-2-hydroxylphenyl)benzothiazole(4-TfmBTZ)as an ancillary ligand using the Gaussian 03 program.The geometries,electronic structures and spectroscopic properties of this iridium(Ⅲ)complex are investigated by density functional theory(DFT)and time−dependent density functional theory(TD-DFT).The results show that the spin-orbit coupling occurs not only between ppy and iridium atom but also between 4-TfmBTZ and iridium atom in this complex.The highest occupied molecular orbital is dominantly localized on the Ir atom and 4-TfmBTZ ligand,while the lowest unoccupied molecular orbital on 4-TfmBTZ ligand.The triplet lowest-lying transition is attributed to the Ir-to-4-TfmBTZ charge-transfer(3MLCT)transition while the sub−low-lying transitions are assigned to the 3MLCT transitions of Ir(ppy)2.The nature of the lowest unoccupied orbital changes from ppy−localized to 4-TfmBTZ-localized and reveals that phosphorescent color of Ir(Ⅲ)complex can be controlled by the ancillary ligand and substituent.