文章基本信息

标题：Structure of an Iron(II) Dioxygen Complex; A Model for Oxygen Carrying Hemeproteins
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作者：James P. Collman ; Robert R. Gagne ; Christopher A. Reed 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1974
卷号：71
期号：4
页码：1326-1329
DOI：10.1073/pnas.71.4.1326
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The preliminary structural characterization of a reversible ferrous dioxygen complex is reported. Mono(N-methyl imidazole) (dioxygen) meso-tetra ([α],[α],[α],[α]-o-pivalamidephenyl) porphinatorino(II), [Fe(O2)-(N-Me imid) ([α],[α],[α],[α]-TpivPP)], 1, isolated from toluene solution, crystallizes in the monoclinic system with four molecules in a unit cell of dimensions a = 18.690 (3), b = 19.514 (3), c = 18.638 (3) A, and {beta} = 91.00 (1){degrees}. R = 0.15 for 841 reflections having F2 > 3{sigma} (F2). The complex 1 has four pivalamido groups on one side of the porphyrin forming a hydrophobic pocket of 5.4-A depth which encloses coordinated dioxygen. The dioxygen is coordinated "end-on," with a bent Fe-O-O bond. The Fe-O-O plane bisects an N-Fe-N right angle of the equatorial iron porphyrin plane and is four way statistically disordered. In addition there is a crystallographic 2-fold axis through iron, coordinated oxygen, and nitrogen of the axially bound N-methyl imidazole. Thus there are two types of coordinated dioxygen with the Fe-O-O plane either parallel or perpendicular to the trans axial imidazole plane. Corresponding values for the Fe-O-O bond angles are 135-(4){degrees} and 137(4){degrees} and for the O-O bond lengths are 1.23 (0.08) and 1.26 (0.08) A, with a dihedral angle of 90{degrees} between alternative orientations of the Fe-O-O plane. The Fe-O distance is 1.75 (0.02) A and Fe-N (imidazole) is 2.07 (0.02) A, suggesting multiple bond character in the Fe-O moiety. The similarity of the Mossbauer spectrum of the model complex, 1, with oxyhemoglobin indicates that 1 may be a good model for oxygen binding in the oxygen transport hemeproteins.
关键词：picket fence porphyrin ; x-ray diffraction