Synthetic control and empirical prediction of redox potentials for Co4O4 cubanes over a 1.4 V range: implications for catalyst design and evaluation of high-valent intermediates in water oxidation. Issue 6 (20th April 2017)

• Record Type: Journal Article
• Authors: Nguyen, Andy I.; Wang, Jianing; Levine, Daniel S.; Ziegler, Micah S.; Tilley, T. Don
• Is Part Of: Chemical science. Volume 8:Issue 6(2017)
• Page Start: 4274
• Page End: 4284
• Publication Date: 2017-04-20
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c7sc00627f
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : The oxo-cobalt cubane unit [Co4 O4 ] is of interest as a homogeneous oxygen-evolution reaction (OER) catalyst, and as a functional mimic of heterogeneous cobalt oxide OER catalysts. Abstract : The oxo-cobalt cubane unit [Co4 O4 ] is of interest as a homogeneous oxygen-evolution reaction (OER) catalyst, and as a functional mimic of heterogeneous cobalt oxide OER catalysts. The synthesis of several new cubanes allows evaluation of redox potentials for the [Co4 O4 ] cluster, which are highly sensitive to the ligand environment and span a remarkable range of 1.42 V. The [CoIII4O4 ] 4+ /[CoIII3Co IV O4 ] 5+ and [CoIII3Co IV O4 ] 5+ /[CoIII2CoIV2O4 ] 6+ redox potentials are reliably predicted by the p K a s of the ligands. Hydrogen bonding is also shown to significantly raise the redox potentials, by ∼500 mV. The potential-p K a correlation is used to evaluate the feasibility of various proposed OER catalytic intermediates, including high-valent Co-oxo species. The synthetic methods and structure–reactivity relationships developed by these studies should better guide the design of new cubane-based OER catalysts.