2‐Phenylquinoline‐Based Cyclometalated Platinum(II) Complexes: Synthesis and Structure–Photoelectric Properties Relationship in Oxygen Sensing

Abstract

Abstract Novel 2‐phenylquinoline‐based cyclometalated Pt II complexes are synthesized and fully characterized. 2‐Phenylquinoline derivatives with a functional group at the 4‐position of the phenyl ring are prepared through an efficient Pd‐catalyzed ligand‐free and aerobic Suzuki reaction of 2‐bromoquinoline with arylboronic acids. The photophysical properties of the complexes demonstrate that the introduction of a diphenylamino group at the 4‐position of the phenyl ring affects the HOMO level of the Pt II complex significantly, resulting in a marked decrease in energy gap. The emission or energy gap is not influenced clearly by other substituents (methyl, cyano, fluoro, trifluoromethyl, methoxyl, carbazol‐9‐yl) at the 4‐position of the phenyl ring. All the complexes show redshifted room‐temperature phosphorescence emission (at 578–599 nm) relative to the model complex Pt(ppy)acac (at 486 nm). The oxygen sensitivity of the complexes is evaluated quantitatively in a polymer film. The films containing the Pt II complexes are sensitive to O 2 , and the luminescence changes gradually and reversibly with O 2 concentration. The Pt II complex with a triphenylamino moiety exhibits the highest sensitivity ( ${K{{app\hfill \atop SV\hfill}}}$ =0.020 Torr −1 ). The 2‐phenylquinoline‐based Pt II complexes are potential candidates for efficient luminescent oxygen sensing. The present results provide a systematic study on the structure–property relationship between the 2‐phenylquinoline‐based Pt II complexes and oxygen sensing.