Selective Formation of 1:1 Dyads of a Saddle‐Distorted Sn(IV)‐Porphyrin as an Acceptor With Donor Molecules as Axial Ligands for Photoinduced Electron Transfer

We have revealed that a 1:1 complex can be selectively formed with a saddle‐distorted Sn IV ‐dodecaphenylporphyrin, Sn IV (DPP), and sterically hindered p ‐ferrocenylbenzoate derivatives through axial coordination of the carboxy group to the Sn IV center of Sn IV (DPP). In the 1:1 complex, we observed photoinduced electron transfer (PET) from the ferrocene moiety as an electron donor to the singlet excited state of the Sn IV (DPP) moiety as an electron acceptor and analyzed the PET by femtosecond transient absorption spectroscopy. The rate constant of the PET was determined to be k ET = (1.35 ± 0.03) × 10 10 s –1 , for p ‐ferrocenylbenzoate as an electron donor. We observed the reduced species of Sn IV (DPP) in the charge‐separated state with a nanosecond‐order lifetime and also revealed that, considering the Marcus theory of electron transfer, the PET proceeded with relatively small reorganization energy of 0.75 eV. The function of Sn IV (DPP) as an electron acceptor is unprecedented. Consequently, we have revealed that Sn IV (DPP) works as a good electron acceptor in the PET system, based on the axial coordination of an electron donor to the metal center.