Reactivity and Mechanisms of Photoactivated Heterometallic [RuIINiII] and [RuIINiIIRuII] Catalysts for Dihydrogen Generation from Water

Two heterometallic photocatalysts were designed and probed for water reduction. Both [(bpy)(2)(RuNiII)-Ni-II(L-1)](ClO4)(2) (1) and [(bpy)(2)(RuNiII)-Ni-II(L-2)(2)Ru-II(bpy)(2)](ClO4)(2) (2) can generate the low-valent precursor involved in hydride formation prior to dihydrogen generation. However, while the bimetallic [(RuNiII)-Ni-II] (1) requires the presence of an external photosensitizer to trigger catalytic activity, the trimetallic [(RuNiRuII)-Ni-II-Ru-II] (2) displays significant coupling between the catalytic and light-harvesting units to promote intramolecular multielectron transfer and perform photocatalysis at the Ni center. A concerted experimental and theoretical effort proposes mechanisms to explain why 1 is unable to achieve self-supported catalysis, while 2 is fully photocatalytic.

Automated summary

Two heterometallic photocatalysts were designed and tested for water reduction, with one requiring an external photosensitizer to trigger catalytic activity and the other displaying significant coupling between catalytic and light-harvesting units for self-supported photocatalysis.