Near-Infrared Light-Driven Hydrogen Evolution from Water Using a Polypyridyl Triruthenium Photosensitizer

摘要

In order to realize artificial photosynthetic devices for splitting water to H-2 and O-2 (2H(2)O + hv - 2H(2) + O-2), it is desirable to use a wider wavelength range of light that extends to a lower energy region of the solar spectrum. Here we report a triruthenium photosensitizer [Ru-3(dmbpy)(6)(mu-HAT)](6+) (dmbpy = 4,4'-dimethyl-2,2'-bipyridine, HAT = 1,4,5,8,9,12-hexaazatriphenylene), which absorbs near-infrared light up to 800 nm based on its metal-to-ligand charge transfer ((MLCT)-M-1) transition. Importantly, [Ru-3(dmbpy)(6)(mu-HAT)](6+) is found to be the first example of a photosensitizer which can drive H-2 evolution under the illumination of near-infrared light above 700 nm. The electrochemical and photochemical studies reveal that the reductive quenching within the ion-pair adducts of [Ru-3(dmbpy)(6)(mu-HAT)](6+) and ascorbate anions affords a singly reduced form of [Ru-3(dmbpy)(6)(mu-HAT)](6+), which is used as a reducing equivalent in the subsequent water reduction process.