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(III) complexes
of type [(X2C^N)2Ir­(Q2bpy)]+PF6– (where X2C^N is 2-phenylpyridine
or 2-(2,4-difluorophenyl)­pyridine anion and Q2bpy 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.