Synthesis and Opto‐electronic Properties of a Red‐Emitting Heteroleptic Platinum Complex Using Pyrazol‐based Diketone Derivative as Ancillary Ligand

A red‐emitting heteroleptic cyclometalated platinum(II) complex containing an ancillary ligand of pyrazol‐based diketone derivative was synthesized. Its optophysical and electroluminescent properties were studied. Compared to the reported (piq)Pt(acac) complex, this platinum(II) complex exhibited a blue‐shifted UV absorption band at 300–450 nm, a low LUMO energy level and improved electroluminescent property. Using this platinum(II) complex as a single doping emitter and a blend of ploy(9,9‐dioctylfluorene) and 2‐tert‐butylphenyl‐5‐phenyl‐1,3,4‐oxadiazole as a host matrix, the fabricated polymer light‐emitting devices displayed saturated red emission with a peak at 648 nm and a shoulder at 601 nm. Furthermore, the emission quenching of the platinum(II) complex was significantly suppressed in these devices at high current density due to an introduction of the non‐planar pyrazol group into the ancillary ligand.