Recent Advances on Phosphorescent Cycloplatinated Compounds Containing Tetradentate Nitrogen Ligands for OLED Applications

Tetradentate Pt(II) emitters have attracted great interest since they can be used as dopants for organic light emitting diodes (OLEDs). These compounds benefit from the square-planar geometry of Pt(II) and the rigidity of the tetradentate ligand. Cyclometallated ligands are particularly appealing since they are thermally stable and display a high ligand field splitting which favours efficient emission. The photophysical properties of these complexes can be tuned by structural modifications, introduction of substituents or control of the intermolecular interactions. Several of the studied compounds have been successfully tested for electroluminescent devices. An overview of the advances reported in this field for the last five years is presented in this work.