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Modeling near-edge ...
Abstract
Ämnesord
Stäng
- The Mn 1s near-edge absorption fine structure (NEXAFS) has been computed by means of transition-state gradient-corrected density functional theory (DFT) on four Mn 4Ca clusters modeling the successive S 0 to S 3 steps of the oxygen-evolving complex (OEC) in photosystem II (PSII). The model clusters were obtained from a previous theoretical study where they were determined by energy minimization. They are composed of Mn(III) and Mn(IV) atoms, progressing from Mn(III) 3Mn(IV) for S 0 to Mn(III) 2Mn(IV) 2 for S 1 to Mn(III)Mn(IV) 3 for S 2 to Mn(IV) 4 for S 3, implying an Mn-centered oxidation during each step of the photosynthetic oxygen evolution. The DFT simulations of the Mn 1s absorption edge reproduce the experimentally measured curves quite well. By the half-height method, the theoretical IPEs are shifted by 0.93 eV for the S 0 → S 1 transition, by 1.43 eV for the S 1 → S 2 transition, and by 0.63 eV for the S 2 → S 3 transition. The inflection point energy (IPE) shifts depend strongly on the method used to determine them, and the most interesting result is that the present clusters reproduce the shift in the S 2 → S 3 transition obtained by both the half-height and second-derivative methods, thus giving strong support to the previously suggested structures and assignments.
Ämnesord
- NATURVETENSKAP -- Kemi (hsv//swe)
- NATURAL SCIENCES -- Chemical Sciences (hsv//eng)
Nyckelord
- Absorption edges
- Absorption fine structure
- Catalytic sites
- Clusters modeling
- Energy minimization
- Fine structures
- Gradient-corrected density functional theory
- Inflection points
- Oxygen evolution
- Oxygen-evolving complexes
- Photosystem II
- Theoretical study
- Transition-state
- Water oxidation
- X-ray spectra
- Catalytic oxidation
- Density functional theory
- Manganese
- oxygen
- water
- article
- catalysis
- chemical structure
- energy
- molecular model
- oxidation
- photosynthesis
- roentgen spectroscopy
Publikations- och innehållstyp
- ref (ämneskategori)
- art (ämneskategori)
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