Issue 10, 2013

Role of oxido incorporation and ligand lability in expanding redox accessibility of structurally related Mn4 clusters

Abstract

Photosystem II supports four manganese centers through nine oxidation states from manganese(II) during assembly through to the most oxidized state before O2 formation and release. The protein-based carboxylate and imidazole ligands allow for significant changes of the coordination environment during the incorporation of hydroxido and oxido ligands upon oxidation of the metal centers. We report the synthesis and characterization of a series of tetramanganese complexes in four of the six oxidation states from MnII3MnIII to MnIII2MnIV2 with the same ligand framework (L) by incorporating four oxido ligands. A 1,3,5-triarylbenzene framework appended with six pyridyl and three alkoxy groups was utilized along with three acetate anions to access tetramanganese complexes, Mn4Ox, with x = 1, 2, 3, and 4. Alongside two previously reported complexes, four new clusters in various states were isolated and characterized by crystallography, and four were observed electrochemically, thus accessing the eight oxidation states from MnII4 to MnIIIMnIV3. This structurally related series of compounds was characterized by EXAFS, XANES, EPR, magnetism, and cyclic voltammetry. Similar to the ligands in the active site of the protein, the ancillary ligand (L) is preserved throughout the series and changes its binding mode between the low and high oxido-content clusters. Implications for the rational assembly and properties of high oxidation state metal–oxido clusters are presented.

Graphical abstract: Role of oxido incorporation and ligand lability in expanding redox accessibility of structurally related Mn4 clusters

Supplementary files

Article information

Article type
Edge Article
Submitted
20 5 2013
Accepted
18 7 2013
First published
19 7 2013

Chem. Sci., 2013,4, 3986-3996

Role of oxido incorporation and ligand lability in expanding redox accessibility of structurally related Mn4 clusters

J. S. Kanady, R. Tran, J. A. Stull, L. Lu, T. A. Stich, M. W. Day, J. Yano, R. D. Britt and T. Agapie, Chem. Sci., 2013, 4, 3986 DOI: 10.1039/C3SC51406D

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