Thermodynamic viability of hydrogen atom transfer from water coordinated to the oxygen-evolving complex of photosystem II
- Univ. of Michigan, Ann Arbor, MI (United States)
Critical to any evaluation of the role of proton transfer in S-state advancement is understanding of proton-coupled electron transfer effects in model manganese complexes in high oxidation states. In an initial attempt to address this hypothesis through biologically relevant model complexes, our group has recently measured the homolytic bond dissociation energy (BDE{sub OH}) for a bridging hydroxide ligand in Mn{sup III}Mn{sup IV}({mu}-O, {mu}-OH)(salpn){sub 2} dimers (salpn = 1,3-bis(salicylideneamino)propane) to be 77-({+-}3) kcal/mol. The data presented here show that the BDE{sub OH} for water directly bound to a higher-valent Mn complex is dramatically less than that for a simple bulk water. The most recent data on the structure and function of Y{sub z}{center_dot} combined with the model studies reported here make a circumstantial though compelling case for hydrogen atom transfer from a ligated water to Y{sub z}{center_dot} as the mechanism for the stepwise cluster oxidation in the OEC. 16 refs., 2 figs., 2 tabs.
- OSTI ID:
- 535448
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 14 Vol. 119; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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