Near-infrared emitting pyrazole-bridged binuclear platinum complexes: Synthesis, photophysical and electroluminescent properties in PLEDs

Abstract

Two novel near-infrared emitting binuclear platinum (II) complexes were successfully designed and synthesized with the bridged ancillary ligand of 3,5-dimethyl pyrazol, in which 2-(pyren-1-yl) pyridine and its derivative of 2-(7-(tert-butyl)pyren-1-yl)pyridine were used as cyclometalated ligands, respectively. Their photophysical, thermal, electrochemical, as well as electro-luminescent properties were investigated. The intrinsic near-infrared electro-luminescent spectra peaked at 692 nm with a shoulder at 753 nm was observed in the single-emissive-layer polymer light-emitting diodes using both binuclear platinum (II) complexes as the dopant. The tert-butyl group attached in pyrenyl ring was found to play an important role in improving electroluminescent properties. Better electroluminescent properties were obtained for the platinum complex with 2-(7-(tert-butyl)pyren-1-yl)pyridine in the devices with a maximum external quantum efficiency of 0.15% and a radiant intensity of 19.10 μW cm−2. To our best knowledge, this is a first reported example on the near-infrared electroluminescence of binuclear platinum complex containing pyrazoline auxiliary ligand.