The Role of the -OH Groups within Mn Clusters in Electrocatalytic Water Oxidation.

The formidable reactivity of the oxygen-evolving center near photosystem II is largely based on its protein environment that stabilizes it during catalysis. Inspired by this concept, the water-soluble Mn clusters Mn O (O CC H (OH) ) (H O) (3,5DHMn ) and Mn O (O CC H (OH) ) (H O) (3,4,5THMn ) were developed as efficient electrocatalysts for water oxidation. In this work, the role of the -OH groups in the electrocatalytic process was explored by describing the structural and electrocatalytic properties of two new Mn clusters, 3,4DHMn and 2,3DHMn , having one -OH group in the meta position relative to the benzoate-Mn moiety, and one at the para or ortho position, respectively. The Mn centers in 3,4DHMn were discovered to have lower oxidation potential compared with those in 2,3DHMn , and thus, 3,4DHMn can catalyze water oxidation with higher rate and TON than 2,3DHMn . Hence, the role of the -OH groups in the electrocatalysis was established, being involved in electronic stabilization of the Mn centers or in proton shuttling.