RESUMO
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 Mn12 clusters Mn12 O12 (O2 CC6 H3 (OH)2 )16 (H2 O)4 (3,5DHMn12 ) and Mn12 O12 (O2 CC6 H3 (OH)3 )16 (H2 O)4 (3,4,5THMn12 ) 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 Mn12 clusters, 3,4DHMn12 and 2,3DHMn12 , 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 3,4DHMn12 were discovered to have lower oxidation potential compared with those in 2,3DHMn12 , and thus, 3,4DHMn12 can catalyze water oxidation with higher rate and TON than 2,3DHMn12 . 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.