Highly Phosphorescent Cyclometalated Iridium(III) Complexes for Optoelectronic Applications: Fine Tuning of the Emission Wavelength through Ancillary Ligands

A series of novel, highly phosphorescent cyclometalated iridium(M) complexes of type [(X2C boolean AND N)(2)Ir(Q(2)bpy)]+PF6- (where X2C boolean AND N is 2-phenylpyridine or 2-(2,4-difluorophenyl)pyridine anion and Q(2)bpy are 4,4'-bifunctionalized 2,2'-bipyridines) is presented. The complexes were fully characterized by means of NMR spectroscopy, high-resolution mass spectrometry (HRMS), cyclic voltammetry, and UV-vis. For several compounds also the crystallographic structures were obtained. The cyclometalates exhibited efficient photoluminescence at 298 K both in solution and in the solid state with good intensity and color purity. The emission wavelength range covered almost the whole visible spectrum and was strongly correlated with the EWG/ERG character of the Q substituent in the ancillary ligand. For further insight into the electronic structure of the complexes, a comprehensive electrochemical support (CV) was introduced, and finally, it was confronted with theoretical background using a density functional theory approach together with time-dependent calculations of the excited states.