Thermodynamic Viability of Hydrogen Atom Transfer from Water Coordinated to the Oxygen-Evolving Complex of Photosystem II

New Mononuclear Manganese(III) Complexes with Hexadentate (N4O2) Schiff Base Ligands: Synthesis, Crystal Structures, Electrochemistry, and Electron‐Transfer Reactivity towards Hydroxylamine

“…) is similar to that of the OϪH group of tyrosine (85.5 kcal·mol Ϫ1 ), [10,11] and so proton movement Ϫ as observed with tyrosine in PSII Ϫ may have some relevance to the observed reactions with hydroxylamine. Atom-labeling schemes and molecular views of complex 1 and 4 are shown in Figures 1 and 2, respectively, while selected bond lengths and angles are given in Tables 1 and 2, respectively.…”

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

“…The pK a of the oxo bridges in 5 are sensitive to the oxidation state of the manganese sites and have been predicted to drop approximately 10.5 pK a units upon oxidation of a Mn center [76]. When a modified salpn ligand, which creates a bridging oxo species by virtue of a tethered alkoxide, is used to form binuclear manganese complex 6, the molecule is known to reversibly bind water and engage in HAT reactivity [77]. The strength of the O-H bond in 6-H 2 O is measured to be 85 kcal mol −1 ; upon initial oxidation (0.54 V in 16 M H 2 O/MeCN vs. NHE), the bond strength is increased to 89 kcal mol −1 .…”

Functional models for the oxygen-evolving complex of photosystem II

“…10-20 turnovers using tert-butylhydrogenperoxide (TBHP) and with less efficiency using cerium(IV) as an oxidant (Table 1). In this system, the use of TBHP is an interesting choice of oxidant due to its tendency toward radical chemistry [90,91]. The authors address the concerns of water oxidation from radical versus oxo-based chemistry by repeating their water-oxidation experiments using ceric ammonium nitrate as the oxidant.…”