C∧ C* cyclometalated platinum (II) NHC complexes with chelating acetylacetonate ligands have been recently shown to be an interesting class of phosphorescent emitters. We sought to clarify the role of the acetylacetonate ligand by replacing one of the coordinating oxygen atoms in the auxiliary ligand with an NH group. This allowed us to study the effect on the emission, and we found that the nature of the emission process changes significantly. We ...