The New Iridium(III) Pyridyltetrazolate Complexes for Blue Phosphorescence

Abstract

A series of new blue-phosphorescent iridium complexes containing phenypyridine (ppy) derivatives and pyridyltetrazole were synthesized and their photophysical and electroluminescent properties were investigated. In the complex, the phenyl moiety which is mostly the highest occupied molecular orbital (HOMO) site was modified with the electron-withdrawing groups F and CF3. By doing so, the emission maxima were expected to shift hypsochromically due to the HOMO level decrease. Furthermore, addition of the modest electron donating group, CH3, to the pyridyl moiety in the ligand could slight raise the lowest unoccupied molecular orbital (LUMO) level of the complex. Therefore, the energy gap increase of the main ligands, phenylpyridine derivatives, might lead to blue emission of their iridium complexes. Previously reported pyridyltetrazole, an ancillary ligand, were also introduced to the iridium complexes for efficient blue phosphorescence and charge balance. The complexes prepared herein exhibited the blue emission at 467 and 486 nm with a shoulder peak at the longer wavelengths, respectively. We also investigated the luminescence properties of the complexes in a polymer film of PMMA (poly(methylmetacrylate)) for their application to the solution process. The photoemission of the complex in PMMA showed similar pattern with that of the complex itself.