Green, near-infrared electroluminescence of novel yttrium tetrazole complexes

Abstract

Four novel yttrium complexes with the molecular formula Y(Tz)_n(x)₂(SCN)_3−n(H₂O), n = 2, 3 and x = phen, bpy, were synthesized by the reactions of yttrium salt with 5-phenyl tetrazole (Tz), 1,10-phenanthroline (phen), 2,2-bipyridine (bpy) and thiocyanate ions, and were used as the emitting material in electroluminescent devices. The structures of these complexes were determined by UV-visible and FT-IR spectroscopy, ¹H NMR, CHN analysis and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The monodentate mode of the Tz complexes was investigated by FT-IR spectroscopy. The different structures of the compounds suggest the importance of the tetrazole and auxiliary ligands in the emission properties of the yttrium complexes. It was found that the Y–polypyridine complexes dressed by tetrazole antennas have highly efficient intra-energy transfer. The Y complexes exhibited broad ligand-centered electroluminescence with maximum near 550 nm, and near-IR electroluminescence at 800, 900 and 950 nm. The electroluminescence spectra of the yttrium complexes indicated a long red shift in the visible region compared to the PVK:PBD blend. The reaction details and features were described and discussed.