The use of vibrational spectroscopy in determining types of excited states is discussed.
Focus is given to metal polypyridyl complexes in which metal-to-ligand charge-transfer is important.
More complex systems with a number of close lying low energy excited states are described, such as dipyridophenazine complexes.
Engineered multichromophore systems are described in which there is weak and strong inter-chromophore coupling.