Abstract
We have covalently connected the ruthenium trisbipyridine complex (bpyRu) as a photoredox module to an iron porphyrin catalyst (porFe) through an amido function for investigating the synergistic action to power the photocatalytic CO2 reduction. The electrochemical studies of the porFe-bpyRu dyad did not show any marked effect on the redox properties of the constitutive units. However, the photophysical properties of the porFe-bpyRu dyad point to the complete extinction of the photoredox module that undergoes ultrafast quenching processes with the porFe acolyte, the unavoidable dilemma in this type of molecular assemblies. Nevertheless, when exogenous bpyRu and a sacrificial electron donor were added to this dyad, we found that it exhibits much higher turnover number and selectivity towards CO2 photocatalytic reduction to CO than with the iron porphyrin analogue (porFe). Comprehensive analyses of the data suggest that this catalytic enhancement displayed by the dyad can be attributed to an interesting electron relay role played by the appended bpyRu moiety.
Highlights
At longer time scale (>60 μs in Figure 5(c)), this Fe(I) species decays back to the Fe(II) state after charge recombination with oxidized Asc·+ (Fe(I) + Asc·+ → Fe(II) + Asc) with a time constant of 610 μs. These photophysical investigations have shown that when the porFe-bpyRu dyad is assimilated as only the catalyst in the presence of exogenous ruthenium (II) trisbipyridine photosensitizer and a sacrificial electron donor, three electrons can be accumulated on the catalyst to form the Fe(I)–Ru(II) species: one electron coming from a dark reaction with the electron donor and two electrons coming from the photo-induced Ru(I) reductant
We have synthetized a new photoredox-catalyst couple, the porFe-bpyRu, where a ruthenium (II) trisbipyridine photosensitizer bpyRu is covalently attached to an iron porphyrin catalyst porFe through an amide linker
A comparative electrochemical study points to a change in the electrocatalytic pattern of the porFe-bpyRu dyad compared to the porFe catalyst
Summary
To the best of our knowledge, there are no reported supramolecular dyads consisting of an iron porphyrin catalyst and any photosensitizer [30]. Laser flash photolysis studies demonstated that upon excitation of the photosensitizer in the dyad, an efficient energy transfer occurs towards the porphyrin catalyst, leading to a very fast quenching (
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