Effective electroluminescent materials for OLED applications based on lanthanide 1.3-diketonates bearing pyrazole moiety

Abstract

A series of new pyrazole substituted 1.3-diketones bearing fluorinated alkyl groups were prepared and systematically explored as a ligands for the preparation of luminescent complexes with Eu(III) ion. First triplet levels energy values (T1) of above mentioned ligands were determined by low temperature (77K) phosphorescent spectra measurements of Gd(III) complexes. It was found that 4,4,5,5,6,6,6-heptafluoro-1-(1-methyl-1H-pyrazol-4-yl)hexane-1,3-dione is a superior ligand for synthesis of highly luminescent Eu (III) complexes with 1.10-phenanthroline or similar Lewis bases as auxiliary ligands. The complexes are sufficiently thermal stable, transparent, volatile in high vacuum and soluble in common solvents which make possible to produce OLEDs by dry and wet technology. OLED structures fabricated on the base of the above Eu(III) complexes demonstrated the higher energy efficacy comparing to the standard Eu(TTA)3(Phen) phosphor.