Spectroscopy of mixed-valence CuA-type centers:: Ligand-field control of ground-state properties related to electron transfer

被引:171
作者
Gamelin, DR
Randall, DW
Hay, MT
Houser, RP
Mulder, TC
Canters, GW
de Vries, S
Tolman, WB
Lu, Y
Solomon, EI [1 ]
机构
[1] Stanford Univ, Dept Chem, Stanford, CA 94305 USA
[2] Univ Illinois, Dept Chem, Urbana, IL 61801 USA
[3] Univ Minnesota, Dept Chem, Minneapolis, MN 55455 USA
[4] Univ Minnesota, Ctr Met Biocatalysis, Minneapolis, MN 55455 USA
[5] Delft Univ Technol, Dept Microbiol & Enzymol, NL-2628 BC Delft, Netherlands
[6] Leiden Univ, Leiden Inst Chem, Gorlaeus Labs, NL-2300 RA Leiden, Netherlands
关键词
D O I
10.1021/ja973161k
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Using a combination of electronic spectroscopies, electronic structural descriptions have been developed for a series of binuclear Cu-A-type centers in Bacillus subtilis CcO and engineered into the blue copper proteins Pseudomonas aeruginosa azurin and Thiobacillus versutus amicyanin. Parallel descriptions are developed for two structurally characterized mixed-valence (MV) and homovalent (II,II) synthetic copper thiolate dimers. Assignment of the excited-state spectral features allows the electronic structures of Cu-A and the MV model to be understood and compared in relation to their copper coordination environments. These electronic structural descriptions are supported by SCF-X alpha-SW MO calculations, which are used to test systematically the effects of major structural perturbations linking the MV model geometry to that of CUA It is determined that both Cu-Cu compression and removal of the axial ligands are critical determinants of the orbital ground state in these dimers. The weakened axial interactions in CUA appear to parallel the mechanism for protein control of electron transfer (ET) function observed in blue copper centers. The major geometric and electronic features of Cu-A, including metal-ligand covalency, redox potentials, reorganization energies, valence delocalization, and the weakened axial bonding interactions, are discussed in relation to its ET function, and specific potential ET pathways are identified and compared.
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页码:5246 / 5263
页数:18
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