Ligand-induced symmetry breaking and concomitant blueshift in the emission wavelength of an octahedral chromium complex.

The resulting distortion of the octahedral symmetry of the complex [CrIII(NH3)6]3+ upon replacing the axial ligands with halides (i.e., weaker ligands) affects the stability of the doublet state with respect to that of the quartet ground state. This substitution affects the doublet-to-quartet transition responsible for phosphorescence. The position of the halide with respect to ammonia in the spectrochemical series is a major influence on the emission wavelength of the complex. The close proximity of fluorine and ammonia in the spectrochemical series leads to a blueshift in the emission wavelength when fluoride ions are introduced into the complex, thus providing a rational approach to the design of blue-phosphorescent materials, which are desirable for OLEDs used in full-color displays. Graphical abstract Shifts in the phosphorescence emission wavelength of an octahedral Cr(III) complex caused by axial ligand substitution. Replacing the axial ligands leads to a change in the relative positions of the axial and equatorial ligands in the spectrochemical series, which in turn induces a redshift or a blueshift in the emission wavelength.