Orange-Red Phosphorescent Iridium(III) Complexes Bearing Bisphosphine Ligands: Synthesis, Photophysical and Electrochemical Properties, and DFT Calculations

Nine new phosphorus-coordinated iridium(III) complexes of the form [Ir(C boolean AND N)(2)(P<^>P)]PF6, [Ir(F-piq)(2)(xantphos)]PF6 (1), [Ir(F-piq)(2)(binap)]PF6 (2), [Ir(F-piq)(2)(dppp)]PF6 (3), [Ir(Me-piq)(2)(xantphos)]PF6 (4), [Ir(Me-piq)(2)(binap)]PF6 (5), [Ir(Me-piq)(2)(dppp)]PF6 (6), [Ir(CF3O-piq)(2)(xantphos)]PF6 (7), [Ir(CF(3)OPiq)(2()binap)PF6 (8), and [Ir(CF3O-piq)2(dppp)]PF6 (9) (F-piq = 1-(4-fluoropheny1)isoquinoline, Me-piq = 1-(p-tolyl)isoquinoline, CF3O-piq = 1-(4-(trifluoromethoxy)-phenyl)-isoquinoline, xantphos = 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene, binap = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl, dppp = 1,3-bis(diphenylphosphanyl)propane), have been synthesized and fully characterized. The crystal structures of 1, 7, and 9 have been determined by X-ray analysis. The most representative molecular orbital energy-level diagrams and the lowest energy electronic transitions of 1-9 have been calculated with density functional theory (DFT) and time-dependent DFT (TD-DFT). All of the complexes are orange-red emissive with quantum efficiencies of 3.2-24.4% and lifetimes of 1.77-3.19 ps in degassed CH2Cl2 solution at room temperature. These research results reveal that the Me-piq CAN ligand and xantphos P<^>P ligand are beneficial for a red shift of absorption and emission wavelength. Complex 4 has better charge transfer ability, which probably promises its use as a red-phosphorescent material.