Near-infrared electroluminescent lanthanide [Pr(iii), Nd(iii), Ho(iii), Er(iii), Tm(iii), and Yb(iii)] N,O-chelated complexes for organic light-emitting devices

New near-IR electroluminescent complexes of Pr3+, Nd3+, Ho3+, Er3+, Tm3+, Yb3+ with N,O-chelated ligands, Ln2(OON)6 (OON = 2-(2-benzoxyazol-2-yl)phenolate) and Ln2(SON)6 (SON = 2-(2-benzothiazol-2-yl)phenolate), were synthesized by the reaction of Ln[N(SiMe3)2]3 and the corresponding N,O-chelating ligand. X-Ray analysis for the Pr and Nd compounds reveals centrosymmetric dimeric structures of the complexes. The solid-state electronic absorption spectra and the electroluminescent spectra show long-wavelength 4f-4f transitions which provide potential use of the compounds as NIR emitting materials in organic light-emitting devices (OLEDs). When constructing OLEDs based on Ln2(OON)6 and Ln2(SON)6, the best results were achieved with the Nd3+ and Yb3+ complexes, where the NIR wall plug efficiency of the ITO/TPD/Ln-complex/BATH/Yb system is 0.82 and 1.22 mW W-1, respectively.