Oxyl radical required for o-o bond formation in synthetic Mn-catalyst.
DFT calculations using the B3LYP functional support the suggestion that the [(terpy)(H(2)O)Mn(IV)(micro-O)(2)Mn(III)(H(2)O)(terpy)](3+) (terpy=2,2':6,2' '-terpyridine) complex functions as a synthetic O(2) 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 Mn(IV)-oxyl radical. From comparisons with inactive Mn(V)-oxo complexes, it is proposed that radical formation is actually a requirement for O(2) formation activity in Mn-complexes.
Lundberg
Marcus
M
Department of Physics, Stockholm University, AlbaNova University Center, Stockholm Center for Physics, Astronomy and Biotechnology, SE-106 91 Stockholm, Sweden. marc@physto.se
Blomberg
Margareta R A
MR
Siegbahn
Per E M
PE