Transition Metal Complexes as Sensitizers

The wealth of information that has accumulated on ruthenium complexes make them the ideal substrate for studying energy and electron transfer in a variety of applications, and were not ruthenium a very limited resource, one may think of a large-scale use of such complexes, e.g., for solar energy cmiversion. 

A further property that makes transition metal ions tremendously useful in photochemistry is obviously the possibility of complexing several mmio- or polydentate ligands around a number of metal ions and thus to assemble sophisticated structures where electronic and geometric factors drive the photochemical processes. This principle has been largely applied in artificial photosynthesis for optimizing light collection and make migration of excitation toward a specific site preferred. 

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Photosensitized oxidations involve either organic dyes or transition metal complexes as sensitizers. Most organic sensitizers operate in their triplet states, as they are relatively longer lived than the singlet states. 

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