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Oxyl Radical Required for O−O Bond Formation in Synthetic Mn-Catalyst

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journal contribution
posted on 12.01.2004 by Marcus Lundberg, Margareta R. A. Blomberg, Per E. M. Siegbahn
DFT calculations using the B3LYP functional support the suggestion that the [(terpy)(H2O)MnIV(μ-O)2MnIII(H2O)(terpy)]3+ (terpy=2,2‘:6,2‘ ‘-terpyridine) complex functions as a synthetic O2 catalyst. The calculated barrier for O−O bond formation with water is 23 kcal/mol. In this complex, as well as in models of the oxygen evolving complex in PSII, the active species is a MnIV-oxyl radical. From comparisons with inactive MnV-oxo complexes, it is proposed that radical formation is actually a requirement for O2 formation activity in Mn-complexes.