Unique photophysical properties of chlorophyll derivatives linked with CO2-reducing moiety along the Qy axis

•We studied a molecular system for the photochemical CO2 reduction using a red-light.•Novel chlorophylls covalently linked to a rhenium bipyridine were synthesized.•The photophysical properties of the novel complexes were determined and analyzed.•A promising system for an effective photochemical CO2 reduction was constructed.

The electron transport system along the Qy axis of the chlorophyll derivatives has attracted considerable attention. Recently, we achieved the first photochemical CO2 reduction using very low energy light (>650 nm) and a synthetic chlorophyll derivative covalently linked with a rhenium bipyridine complex at the Qy axis. This result prompted us to construct an efficient photochemical CO2 reduction system with harvesting red light absorbed by a chlorophyll electron donor. In this study, we discuss the photophysical properties of modified chlorophyll and rhenium bipyridine conjugates comparing with the original one.

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