Inversion of excited States of transition-metal complexes.

The nature of the emission from central metal ions in complexes can be controlled by chemical alteration of the ligands. For iridium(III) species three types of emission have been observed, each originating from a different and orbitally identifiable excited state. Principles useful for designing new luminescent materials are formulated. They can be used for guiding photochemical research and for designing new analytical methods.