LAUSR

Catalytic water oxidation is an important process for the development of future clean energy solutions and energy storage. Despite a significant number of reported active catalysts, systematic control of the catalytic activity remains elusive. Here, we continue to explore descriptors which can be correlated with catalytic activity. [Ru(tpy)(pic) 2 (H 2 O)](NO 3 ) 2 ( 1 ) and [Ru(EtO-tpy)(pic) 2 (H 2 O)](NO 3 ) 2 ( 2 ) (where tpy = 2,2':6',2″-terpyridine, EtO-tpy = 4'(ethoxy)-2,2':6',2″-terpyridine, pic = 4-picoline), have been synthesized and characterized by NMR, UV-vis, electrochemical analysis, EPR, resonance Raman, and X-ray absorption spectroscopy. Addition of the ethoxy group increases catalytic activity in chemically driven and photocatalytic water oxidation. Thus, the effect of the electron-donating group known for the [Ru(tpy)(bpy)(H 2 O)] 2+ family is transferable to architectures with tpy ligand trans to the Ru-oxo unit. Under catalytic conditions, 2 displays new spectroscopic signals tentatively assigned to a peroxo intermediate. Reaction pathways were analyzed using DFT. Currently 2 is one of the most active catalysts functioning via water nucleophilic attack mechanism.