Polyoxometalates excited state energies

It is known that molecules in photoexcited states are stronger oxidants and reductants than those in the ground states. The potentials of the excited states of polyoxometalates can be estimated by adding the energy of 0,0-transitions to the ground-state reduction potentials (257, 405). 

However, the emission from the excited states of polyoxometalates is usually so weak that it is difficult to determine the 0,0-transition energies exactly (257). 

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