Quenchers cage complexes

Caged Amine complexes of Co(III) The reduced form of Co(III) complexes such as Co(III)(NH3)5X2+ are substitutionally labile. A number of caged cobalt(II) compounds have been found to be fairly inert to substitution. The sar, sep or the sulfur-containing capten cage complexes have [Co(III)/Co(II)] potentials > -0.2V vs NHE are and efficient quenchers of Ru(bpy)3 [41-43]. Some of them have been found use as relays for water photoreduction. 

For excited states of metal complexes that are well characterized, the procedure can be reversed and the free energy dependence of the quenching can, in turn, be used to determine the quencher exchange rates and/or quencher potentials that may be difficult to obtain by other means. For practical applications, the cage escape yield must be high. Laser flash photolysis techniques allow measurement of cage escape yields of redox products and there have been a number of studies reporting such yields for various quenchers. 

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