Our investigations refer to highly efficient emitting materials used in organic light-emitting diodes (OLED). We are
especially interested in the possibility of shifting the emission wavelength in phosphorescent iridium(III) complexes.
Depending on the mesomeric and inductive behavior of different substituents, the emission spectrum can be varied by
introducing those substituents at various positions of the chromophoric ligand. Therefore, we synthesized Ir(ppy)<sub>3</sub>-
analogue complexes with nitrile, trifluoromethyl and methoxy groups at different positions of the ligand's phenyl ring to
determine the influence of the position and of each substituent on the emission spectrum. To further study the
adjustability we prepared several heteroleptic complexes and changed the ancillary ligand therein. In addition, we
developed a new and as yet unknown ligand system based on hetero five membered rings, cyclometalated to iridium to
generate homo- and heteroleptic complexes. Devices obtained with these emitting materials have shown high
luminescence efficiencies of up to 30 lm/W @ 500 cd/m<sup>2</sup>.