Photocatalytic hydrogen generation from water reduction using orchestrated photosensitizers

Vinyl (-CH=CH₂) is a functional group in chlorophyll molecules that are essential in natural photosynthesis, which is crucial for tuning the electronic properties and the interaction between chlorophyll and other biological cofactors. Approaches to apply a vinyl group in artificial photosynthesis have been reported to improve the electron transfer from an iridium complex photosensitizer (PS) to a colloidal platinum catalyst likely by chemical adsorption. However, versatile molecular design of Ir-PSs utilizing a vinyl group is still very important to further develop photocatalytically active compounds. Here we report two new Ir-PSs with a phenylvinyl (styrenyl) moiety in two different positions. Their hydrogen-generation performance was assessed in the presence of a triethylamine electron donor and a colloidal platinum catalyst. As expected, both the Ir-PSs show much higher turnover numbers than the non-styrenylic Ir-PS, and interestingly, the H₂ generation longevity was clearly observed to be dependent on the styrenyl position.