Issue 11, 2016

Mononuclear ruthenium polypyridine complexes that catalyze water oxidation


Over the past decade, significant advances have been made in the development of molecular water oxidation catalysts (WOCs) in the context of developing a system that would accomplish artificial photosynthesis. Mononuclear ruthenium complexes with polypyridine ligands have drawn considerable attention in this regard, due to their high catalytic activity and relatively simple structure. In this perspective review, we will discuss mononuclear Ru polypyridine WOCs by organizing them into four groups according to their ligand environments. Each group will be discussed with regard to three fundamental questions: first, how does the catalyst initiate O–O bond formation? Second, which step in the catalytic cycle is rate-determining? Third, how efficient is the catalyst according to the specific descriptors such as turnover frequency? All discussion is based on the high-valent ruthenium intermediates that are proposed in the catalytic cycle according to experimental observation and theoretical simulation. Two fundamental mechanisms are set forth. An acid–base mechanism that involves the attack of a water molecule on the oxo of a high valent Ru[double bond, length as m-dash]O species to form the O–O bond. Subsequent steps lead to dissociation of O2 and rehydration of the metal center. A second mechanism involves the formation of a Ru–O˙ radical species, two of which then couple to form a Ru–O–O–Ru species that can release O2 afterwards. The acid–base mechanism appears to be more common and mechanistic differences could result from variation directly related to polypyridine ligand structures. Understanding how electronic, steric, and conformational properties can effect catalyst performance will lead to the rational design of more effective WOCs with not only ruthenium but also other transition metals.

Graphical abstract: Mononuclear ruthenium polypyridine complexes that catalyze water oxidation

Article information

Article type
22 Jun 2016
05 Aug 2016
First published
05 Aug 2016
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2016,7, 6591-6603

Author version available

Mononuclear ruthenium polypyridine complexes that catalyze water oxidation

L. Tong and R. P. Thummel, Chem. Sci., 2016, 7, 6591 DOI: 10.1039/C6SC02766K

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity