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Tetranuclear [Mn^(III)Mn_3^(IV)O_4] Complexes as Spectroscopic Models of the S_2 State of the Oxygen Evolving Complex in Photosystem II

Lee, Heui Beom and Shiau, Angela A. and Oyala, Paul H. and Marchiori, David A. and Gul, Sheraz and Chatterjee, Ruchira and Yano, Junko and Britt, R. David and Agapie, Theodor (2018) Tetranuclear [Mn^(III)Mn_3^(IV)O_4] Complexes as Spectroscopic Models of the S_2 State of the Oxygen Evolving Complex in Photosystem II. Journal of the American Chemical Society, 140 (49). pp. 17175-17187. ISSN 0002-7863. PMCID PMC6574184. http://resolver.caltech.edu/CaltechAUTHORS:20181113-112610015

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Abstract

Despite extensive biochemical, spectroscopic, and computational studies, the mechanism of biological water oxidation by the oxygen evolving complex (OEC) of Photosystem II remains a subject of significant debate. Mechanistic proposals are guided by the characterization of reaction intermediates such as the S_2 state, which features two characteristic EPR signals at g = 2 and g = 4.1. Two nearly isoenergetic structural isomers have been proposed as the source of these distinct signals, but relevant structure–electronic structure studies remain rare. Herein, we report the synthesis, crystal structure, electrochemistry, XAS, magnetic susceptibility, variable temperature CW-EPR, and pulse EPR data for a series of [Mn^(III)Mn_3^(IV)O_4] cuboidal complexes as spectroscopic models of the S_2 state of the OEC. Resembling the oxidation state and EPR spectra of the S_2 state of the OEC, these model complexes show two EPR signals, a broad low field signal and a multiline signal, that are remarkably similar to the biological system. The effect of systematic changes in the nature of the bridging ligands on spectroscopy were studied. Results show that the electronic structure of tetranuclear Mn complexes is highly sensitive to even small geometric changes and the nature of the bridging ligands. Our model studies suggest that the spectroscopic properties of the OEC may also react very sensitively to small changes in structure; the effect of protonation state and other reorganization processes need to be carefully assessed.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1021/jacs.8b09961DOIArticle
https://pubs.acs.org/doi/suppl/10.1021/jacs.8b09961PublisherSupporting Information
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6574184PubMed CentralArticle
ORCID:
AuthorORCID
Oyala, Paul H.0000-0002-8761-4667
Marchiori, David A.0000-0001-9738-3674
Gul, Sheraz0000-0001-8920-8737
Chatterjee, Ruchira0000-0002-0865-061X
Yano, Junko0000-0001-6308-9071
Britt, R. David0000-0003-0889-8436
Agapie, Theodor0000-0002-9692-7614
Alternate Title:Tetranuclear [MnIIIMn3IVO4] Complexes as Spectroscopic Models of the S2 State of the Oxygen Evolving Complex in Photosystem II
Additional Information:© 2018 American Chemical Society. Received: September 13, 2018; Published: November 8, 2018. This research was supported by the NIH (R01-GM102687B), the Dreyfus Teacher-Scholar Program (T.A.), Dow Next Generation Educator (instrumentation), NSF-1531940 (Caltech EPR facility), the Division of Chemical Sciences, Geosciences, and Biosciences (R.D.B. Grant DE-SC0007203) of the Office of Basic Energy Sciences of the U.S. Department of Energy. Part of this work (XAS data collection) was carried out at Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract DE-AC02-76SF00515. XAS studies were performed with support of the Office of Science, OBES, Division of Chemical Sciences, Geosciences, and Biosciences (CSGB) of the DOE under contract DE-AC02-05CH11231 (J.Y.). We thank Dr. Michael K. Takase and Mr. Lawrence M. Henling for assistance with X-ray crystallography and Dr. Ignacio B. Martini for SQUID magnetometry. The authors declare no competing financial interest.
Funders:
Funding AgencyGrant Number
NIHR01-GM102687B
Camille and Henry Dreyfus FoundationUNSPECIFIED
Dow Next Generation Educator FundUNSPECIFIED
NSFCHE-1531940
Department of Energy (DOE)DE-SC0007203
Department of Energy (DOE)DE-AC02-76SF00515
Department of Energy (DOE)DE-AC02-05CH11231
PubMed Central ID:PMC6574184
Record Number:CaltechAUTHORS:20181113-112610015
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20181113-112610015
Official Citation:Tetranuclear [MnIIIMn3IVO4] Complexes as Spectroscopic Models of the S2 State of the Oxygen Evolving Complex in Photosystem II. Heui Beom Lee, Angela A. Shiau, Paul H. Oyala, David A. Marchiori, Sheraz Gul, Ruchira Chatterjee, Junko Yano, R. David Britt, and Theodor Agapie. Journal of the American Chemical Society 2018 140 (49), 17175-17187. DOI: 10.1021/jacs.8b09961
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90871
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:13 Nov 2018 21:31
Last Modified:19 Jun 2019 18:05

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