Bioinspired Water-Splitting Catalysts for Artificial Photosynthesis

SIGNORELLA, S. R.

Chascomús

Encuentro; Latin American Meeting on Biological Inorganic chemistry ? IV LABIC and V WOQUIBIO; 2014

UBA

Manganese is low-cost, environmentally friendly, and is used by nature to oxidize water; therefore, Mn compounds are among candidates as biomimetic water oxidizing catalysts.4-6 Most homogeneous manganese-based complexes are able to catalyse water oxidation only if O-transfer oxidants are used, and their activity is strongly improved by using heterogeneous systems.4-6 It must be stressed that although the Mn ligand environment in OEC is mainly oxygen-based,2 most of the Mn complexes evaluated as water-oxidation catalysts contain ligands with high proportion of N-donor sites.4-6 Based on this, efforts need to focus on testing the feasibility of obtaining Mn-based water-splitting catalysts employing ligands with predominant O-donor sites, with different geometrical arrangement around the Mn ions, and compare their activity in homogeneous phase and heterogeneous assemblies based on surface covalent attachment. This integrated effort of ligand design, synthesis and assembly to surfaces started to render some clues for catalysis: in homogeneous phase, efficiency of the tested complexes to catalyze water oxidation by one-electron oxidants strongly depends on the presence of CO2- bound to Mn and the number of such groups in the ligand; in heterogeneous systems, the generation of neighbor substitution-labile axial sites and formation of tetra-Mn clusters from bi-layered adsorbed diMn complexes, are key for catalysis and represent one step forward toward the rational design of water-splitting catalysts for artificial photosynthesis.