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Evaluation of Manganese Cubanoid Clusters for Water Oxidation Catalysis: From Well-Defined Molecular Coordination Complexes to Catalytically Active Amorphous Films.

ABSTRACT: With a view to developing multimetallic molecular catalysts that mimic the oxygen-evolving catalyst (OEC) in Nature's photosystem II, the synthesis of various dicubanoid manganese clusters is described and their catalytic activity investigated for water oxidation in basic, aqueous solution. Pyridinemethanol-based ligands are known to support polynuclear and cubanoid structures in manganese coordination chemistry. The chelators 2,6-pyridinedimethanol (H₂ L¹ ) and 6-methyl-2-pyridinemethanol (HL² ) were chosen to yield polynuclear manganese complexes; namely, the tetranuclear defective dicubanes [Mn^II ₂ Mn^III ₂ (HL¹ )₄ (OAc)₄ (OMe)₂ ] and [Mn^II ₂ Mn^III ₂ (HL¹ )₆ (OAc)₂ ] (OAc)₂ ⋅2 H₂ O, as well as the octanuclear-dicubanoid [Mn^II ₆ Mn^III ₂ (L² )₄ (O)₂ (OAc)₁₀ (HOMe/OH₂ )₂ ]⋅3MeOH⋅MeCN. In freshly prepared solutions, polynuclear species were detected by electrospray ionization mass spectrometry, whereas X-band electron paramagnetic resonance studies in dilute, liquid solution suggested the presence of divalent mononuclear Mn species with g values of 2. However, the magnetochemical investigation of the complexes' solutions by the Evans technique confirmed a haphazard combination of manganese coordination complexes, from mononuclear to polynuclear species. Subsequently, the newly synthesized and characterized manganese molecular complexes were employed as precursors to prepare electrode-deposited films in a buffer-free solution to evaluate and compare their stability and catalytic activity for water oxidation electrocatalysis.

SUBMITTER: Hosseinmardi S

PROVIDER: S-EPMC8596818 | biostudies-literature |

REPOSITORIES: biostudies-literature

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