Synthesis, structures and spectroscopy of three new lanthanide β-diketonate complexes with 4,4′-dimethyl-2,2′-bipyridine. Near-infrared electroluminescence of ytterbium(III) complex in OLED

Abstract Three new lanthanide(III) β-diketonate complexes [Ln(btfa) 3 (4,4′-dmbpy)] ( Ln = Yb(III), Gd(III) and Nd(III); btfa  = anionic 4,4,4-trifluoro-1-phenyl-1,3-butanedione and 4,4′-dmbpy  =  4,4′-dimethyl-2,2′-bipyridine ) were synthesized and their characterization, including elemental analysis, FTIR spectroscopy and thermal analysis (TG/DTA), is reported. The crystal description based on powder X-ray diffraction reveals that Gd(III) and Yb(III) compounds are isostructural and that lanthanide ion is eight-coordinated by oxygen and nitrogen atoms to give new tris- β-diketonates [Ln(btfa) 3 (4,4′-dmbpy)] . The cell parameters of Nd(III) complex are close to Gd(III) and Yb(III) ones. Phosphorescence data of Gd(III) complex shows that the triplet states (T 1 ) of the ligands have higher energy than the emitting states of Yb(III) and Nd(III), indicating the possibility of intramolecular energy transfer to these metal ions, which exhibit near-infrared (NIR) emission. We have used the Yb(III) complex as an emitting layer (EML) in a near infrared organic light emitting diode (NIR-OLED) with the structure: CuPc(15 nm)/XD-03(40 nm)/Yb(60 nm)/BCP(15 nm)/Alq 3 (10 nm)/Al(120 nm). OLEDs exhibit both visible electroluminescence and a NIR electroluminescence at 980 nm from the 2 F 5/2  →  2 F 7/2 transition of the Yb(III).