Oblique bisporphyrins

The excited triplet state of the zinc porphyrin subunit decayed with a lifetime 

Excitation of either porphyrin subunit in this bisporphyrin results in electron transfer from zinc to gold porphyrins to form the respective %-radical ions. For the zinc porphyrin, both singlet and triplet excited states function as electron donors whereas for the gold porphyrin intersystemcrossing to the triplet manifold is quantitative and the triplet acts as an electron acceptor. Consequently, virtually every photon absorbed by the bisporphyrin results in charge separation and the compound provides a unique opportunity to compare singlet and triplet state photoinduced electron transfer processes. 

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A further improvement in the status of bisporphyrin photoredox chemistry came with the synthesis of an oblique zinc(II)/gold(III) bisporphyrin by Sauvage and coworkers [16]. This compound (Figure 7) has a constrained geometry that somewhat resembles the arrangement of the porphyrin... 

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