Crystal structure of a metal ion-bound oxoiron(IV) complex and implications for biological electron transfer.
Critical biological electron-transfer processes involving high-valent oxometal chemistry occur widely, for example in haem proteins [oxoiron(IV); Fe(IV)(O)] and in photosystem II. Photosystem II involves Ca(2+) as well as high-valent oxomanganese cluster species. However, there is no example of an interaction between metal ions and oxoiron(IV) complexes. Here, we report new findings concerning the binding of the redox-inactive metal ions Ca(2+) and Sc(3+) to a non-haem oxoiron(IV) complex, [(TMC)Fe(IV)(O)](2+) (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane). As determined by X-ray diffraction analysis, an oxo-Sc(3+) interaction leads to a structural distortion of the oxoiron(IV) moiety. More importantly, this interaction facilitates a two-electron reduction by ferrocene, whereas only a one-electron reduction process occurs without the metal ions. This control of redox behaviour provides valuable mechanistic insights into oxometal redox chemistry, and suggests a possible key role that an auxiliary Lewis acid metal ion could play in nature, as in photosystem II.
Fukuzumi
Shunichi
S
Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, SORST, Japan Science and Technology Agency, Suita, Osaka 565-0871, Japan. fukuzumi@chem.eng.osaka-u.ac.jp
Morimoto
Yuma
Y
Kotani
Hiroaki
H
Naumov
Pance
P
Lee
Yong-Min
YM
Nam
Wonwoo
W
D000473:Alkanes / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D004583:Electrons; D007501:Iron / Q000737:chemistry*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D012493:Samarium / Q000737:chemistry*
D000473:Alkanes; C066317:ferryl iron; D012493:Samarium; D007501:Iron; D002118:Calcium