Electric field tunable light emitting diodes containing europium β-diketonates with [2.2]paracyclophane moiety

• Europium β-diketonates with [2.2]paracyclophane moiety were synthesized.
• Electroluminescent properties of europium complexes are reported.
• New complexes were used to fabricate organic light emitting diodes (OLEDs).
• Electric field tunable OLED using a single electroluminescent layer was obtained.

The synthesis and electroluminescent (EL) properties of two europium complexes with unsymmetrical β-diketonates and 1,10-phenanthroline are reported. The molecules are substituted by functional groups with different donor–acceptor properties and contain [2.2]paracyclophane moiety. They were used to fabricate the organic light emitting diodes (OLEDs). A large emission wavelength tunability by the applied electric field is observed for OLED containing europium β-diketonate substituted by phenyl group, with the maximum of luminance of 8 cd/m2. Such tunability disappears for OLED based on europium β-diketonate substituted by CH3 group, for which the luminance decreases to ca 2.5 cd/m2. Also in that case an emission band in UV disappears. The OLED stability is lower in the latter case too, showing the importance of the substitution on the OLED operation. It shows also a high potential for the electroluminescent properties control and improvement of these Eu based macromolecules through a simple β-diketonate ligand chemical structure modification.