Highly-efficiency red-emitting platinum (II) complexes containing 4′-diarylamino-1-phenylisoquinoline ligands in polymer light-emitting diodes: Synthesis, structure, photoelectron and electroluminescence

Heteroleptic cyclometalated platinum (II) complexes bearing diarylamino-functionalized 1-phenylisoquinoline derivatives as primary ligand and acetyl acetonate as ancillary ligand were prepared and characterized. Single-crystal X-ray diffraction revealed that platinum (II) (4-(isoquinolin-1-yl)-N,N-diphenylbenzenamine-N,C2′) (2,4-pentanedionato-O,O) displayed square planar molecular geometry with Pt···Pt separation of 6.328 and 6.275 Å. The platinum (II) complexes displayed good thermal and morphological stability, as well as intense ligand-centered fluorescence and π–π* phosphorescence at 298 K, as well as strong phosphorescence at 77 K in dichloromethane. The double-layer polymer light-emitting diodes using 6a as emitters and a blend of poly(9,9-dioctylfluorene) and 2-(4-tert-butyl)-phenyl-5-biphenyl-1,3,4-oxadiazole as host matrix exhibit best performance with the maximum external quantum efficiency as high as 8.6% at 0.66 mA cm–2.