Synthesis and application of the novel azomethine metal complexes for the organic electroluminescent devices

Abstract

New azomethine metal complexes were synthesized systematically and characterized. Beryllium, magnesium, or zinc ions were used as a central metal cation and aromatic azomethines (L1-L4) were employed as a chelating anionic ligand. Emission peaks of the complexes in both solution and solid states were observed mostly at the region of 400-500 nm. in the luminescence spectra, where blue light was emitted. Three of them (BeL1 (1), ZnL2 (II), and ZnL3 (III)) were sublimable and thus were applied to the organic light-emitting devices (OLED) as an emitting layer, respectively. The device including the emitting layer of I exhibited white emission with the broad luminescence spectral range. The device with the emitting layer of H showed blue luminescence with the maximum emission peak at 460 rim. Their ionization potentials, electron affinities, and electrochemical band gaps were investigated with cyclic voltammetry. The electrochemical gaps of 2.98 for 1, 2.70 for II, and 2.63 eV for III were found to be consistent with their respective optical band gaps of 3.01, 2.95 and 2.61 eV within an experimental error. The structure of OLED manufactured in this study reveals that these complexes can work as electron transporting materials as well.