Reversible Structural Isomerization of Nature's Water Oxidation Catalyst Prior to O-O Bond Formation

Guo, Y.Center of Artificial Photosynthesis for Solar Fuels and Department of Chemistry, School of Science, Westlake University, Hangzhou 310024, China;Institute of Natural Sciences, Westlake Institute for Advanced Study, Hangzhou 310024, China (författare)

QC 20230421
Photosynthetic water oxidation is catalyzed by a manganese-calcium oxide cluster, which experiences five "S-states" during a light-driven reaction cycle. The unique "distorted chair"-like geometry of the Mn4CaO5(6)cluster shows structural flexibility that has been frequently proposed to involve "open" and "closed"-cubane forms from the S1 to S3states. The isomers are interconvertible in the S1 and S2states, while in the S3state, the open-cubane structure is observed to dominate inThermosynechococcus elongatus (cyanobacteria) samples. In this work, using density functional theory calculations, we go beyond the S3+Yzstate to the S3nYz•→ S4+Yzstep, and report for the first time that the reversible isomerism, which is suppressed in the S3+Yzstate, is fully recovered in the ensuing S3nYz•state due to the proton release from a manganese-bound water ligand. The altered coordination strength of the manganese-ligand facilitates formation of the closed-cubane form, in a dynamic equilibrium with the open-cubane form. This tautomerism immediately preceding dioxygen formation may constitute the rate limiting step for O2formation, and exert a significant influence on the water oxidation mechanism in photosystem II.

Messinger, Johannes,1963-Uppsala universitet,Umeå universitet,Kemiska institutionen,Molecular Biomimetics, Department of Chemistry Ångström Laboratory, Uppsala University, Uppsala, Sweden,Molekylär biomimetik,Department of Chemistry, Umeå University, Linnaeus väg 6 (KBC huset), SE-90187 Umeå, Sweden(Swepub:uu)johme269 (författare)
Kloo, LarsKTH,Kemi,Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden(Swepub:kth)u1jrdr1m (författare)
Sun, L.Center of Artificial Photosynthesis for Solar Fuels and Department of Chemistry, School of Science, Westlake University, Hangzhou 310024, China;Institute of Natural Sciences, Westlake Institute for Advanced Study, Hangzhou 310024, China (författare)
Center of Artificial Photosynthesis for Solar Fuels and Department of Chemistry, School of Science, Westlake University, Hangzhou 310024, China;Institute of Natural Sciences, Westlake Institute for Advanced Study, Hangzhou 310024, ChinaKemiska institutionen (creator_code:org_t)

Ingår i:Journal of the American Chemical Society: American Chemical Society (ACS)144:26, s. 11736-117470002-78631520-5126

Av författaren/redakt...: Guo, Y.; Messinger, Johan ...; Kloo, Lars; Sun, L.

Om ämnet

Av lärosätet: Kungliga Tekniska Högskolan; Umeå universitet; Uppsala universitet

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