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Published January 5, 2015 | Published + Supplemental Material
Journal Article Open

Investigations of the Effect of the Non-Manganese Metal in Heterometallic-Oxido Cluster Models of the Oxygen Evolving Complex of Photosystem II: Lanthanides as Substitutes for Calcium

Abstract

We report the syntheses and electrochemical properties of nine new clusters ([LLnMn^(IV)_(3)O_4(OAc)_3(DMF)_n]^+ (Ln = La^3+, Ce^3+, Nd^3+, Eu^3+, Gd^3+, Tb^3+, Dy^3+, Yb^3+, and Lu^3+, n = 2 or 3)) supported by a ligand (L^3–) based on a 1,3,5-triarylbenzene motif appended with alkoxide and pyridine donors. All complexes were obtained by metal substitution of Ca2+ with lanthanides upon treatment of previously reported LMn_3CaO_4(OAc)_3(THF) with Ln(OTf)_3. Structural characterization confirmed that the clusters contain the [LnMn_3O_4] cubane motif. The effect of the redox-inactive centers on the electronic properties of the Mn_3O_4 cores was investigated by cyclic voltammetry. A linear correlation between the redox potential of the cluster and the ionic radii or pKa of the lanthanide metal ion was observed. Chemical reduction of the LMn^(IV)_3GdO_4(OAc)_3(DMF)2 cluster with decamethylferrocene, resulted in the formation of LGdMn^(IV)_2Mn^(III)O_4(OAc)_3(DMF)_2, a rare example of mixed-valence [MMn_3O_4] cubane. The lanthanide-coordinated ligands can be substituted with other donors, including water, the biological substrate.

Additional Information

© 2014 American Chemical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. Received: June 28, 2014; Published: December 18, 2014. This work was supported by the California Institute of Technology and the NIH R01 GM102687A (T.A.). T.A. is a Sloan, Dreyfus, and Cottrell fellow. We thank Lawrence M. Henling for assistance with crystallography and Zhiji Han for assistance with the characterization of the Ce complexes. The Bruker KAPPA APEXII X-ray diffractometer was purchased via an NSF Chemistry Research Instrumentation award to Caltech (CHE-0639094).

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Created:
August 20, 2023
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October 19, 2023