| Summary: | Three novel Ir(III) complexes, (ppy)<sub>2</sub>Ir(L-alanine) (<b>Ir1</b>) (ppy = 2-phenylpyridine), (F<sub>4</sub>ppy)<sub>2</sub>Ir(L-alanine) (<b>Ir2</b>) (F<sub>4</sub>ppy = 2-(4-fluorophenyl)pyridine), and (F<sub>2,4,5</sub>ppy)<sub>2</sub>Ir(L-alanine) (<b>Ir3</b>) (F<sub>2,4,5</sub>ppy = 2-(2,4,5-trifluorophenyl)pyridine), based on simple L-alanine as ancillary ligands were synthesized and investigated. Due to the introduction of fluorine substituents on the cyclometalated ligands, complexes <b>Ir1</b>–<b>Ir3</b> exhibited yellow to sky-blue emissions (<i>λ</i><sub>em</sub> = 464–509 nm) in acetonitrile solution. The photoluminescence quantum yields (PLQYs) of <b>Ir1</b>–<b>Ir3</b> ranged from 0.48–0.69, of which <b>Ir3</b> with sky-blue luminescence had the highest PLQY of 0.69. The electrochemical study and density functional theory (DFT) calculations show that the highest occupied molecular orbital (HOMOs) energy of <b>Ir1</b>–<b>Ir3</b> are stabilized by the introduction of fluorine substituents on the cyclometalated ligands, while L-alanine ancillary ligand has little contribution to HOMOs and lowest unoccupied molecular orbitals (LUMOs). Moreover, <b>Ir1</b>–<b>Ir3</b> presented an excellent response to Cu<sup>2+</sup> with a high selectivity, strong anti-interference ability, and short response time. Such a detection was based on significant phosphorescence quenching of their emissions, showing the potential application in chemosensors for Cu<sup>2+</sup>.
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