6533b81ffe1ef96bd1278f3b

RESEARCH PRODUCT

Cobaltocenium substituents as electron acceptors in photosynthetic model dyads

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Abstract Cobaltocenium carboxylic acid hexafluorophosphate has been attached to a zinc(II) meso-tetraphenyl porphyrin chromophore via an amide linkage. Optical and electrochemical studies reveal that the metallocene and the porphyrin interact only negligibly in the ground state of the dyad. Photoinduced charge-shift from the zinc porphyrin to the cobaltocenium substituent to give the zinc porphyrin radical cation and the cobaltocene occurs upon exciting the porphyrin with light. Steady state emission, time-resolved fluorescence and transient absorption pump–probe spectroscopy in addition to density functional theory calculations suggest that the charge shift to the cobaltocenium substituent can occur from several excited states of the porphyrin, namely from the S2, S1 and T1 states. The triplet states of the cobaltocenium substituent (3E1g) and the triplet state of the zinc porphyrin (T1) are higher in energy than the charge-shifted state. This energy sequence of states of the dyad is beneficial for photoinduced charge-shift reactions.