Redox Tuning via Ligand-Induced Geometric Distortions at a YMn 3 O 4 Cubane Model of the Biological Oxygen Evolving Complex

• Published in: Inorganic chemistry Vol. 58; no. 22; pp. 14998 - 15003
• Main Authors: Lee, Heui Beom, Agapie, Theodor
• Format: Journal Article
• Language: English
• Published: United States 18.11.2019
• Subjects: Biomimetic Materials - chemistry; Coordination Complexes - chemistry; Electron Transport; Ligands; Manganese Compounds - chemistry; Models, Molecular; Oxidation-Reduction; Oxides - chemistry; Oxygen - chemistry; Photosystem II Protein Complex - chemistry
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.9b00510

The function of proteins involved in electron transfer is dependent on cofactors attaining the necessary reduction potentials. We establish a mode of cluster redox tuning through steric pressure on a synthetic model related to Photosystem II. Resembling the cuboidal [CaMn O ] subsite of the biological oxygen evolving complex (OEC), [Mn O ] and [YMn O ] complexes featuring ligands of different basicity and chelating properties were characterized by cyclic voltammetry. In the absence of ligand-induced distortions, increasing the basicity of the ligands results in a decrease of cluster reduction potential. Contraction of Y-oxo/Y-Mn distances by 0.1/0.15 Å enforced by a chelating ligand results in an increase of cluster reduction potential even in the presence of strongly basic donors. Related protein-induced changes in Ca-oxo/Ca-Mn distances may have similar effects in tuning the redox potential of the OEC through entatic states and may explain the cation size dependence on the progression of the S-state cycle.