X-RAY SPECTROSCOPIC STUDIES OF NICKEL-COMPLEXES, WITH APPLICATION TO THE STRUCTURE OF NICKEL SITES IN HYDROGENASES
X-RAY SPECTROSCOPIC STUDIES OF NICKEL-COMPLEXES, WITH APPLICATION TO THE STRUCTURE OF NICKEL SITES IN HYDROGENASES
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DOI：
10.1021/ic00005a010
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发表时间：
1991-03-06
影响因子：
4.6
通讯作者：
MASCHARAK, PK
中科院分区：
文献类型：
--
作者：
COLPAS, GJ;MARONEY, MJ;MASCHARAK, PK
报道了44个Ni（II）和Ni（III）与N-和/或S-配体配合物的X射线吸收近边光谱（XANES）。 光谱揭示了与1 s-> 3d和1 s-> 4p（z）电子跃迁相关的特征，其存在或不存在以及强度提供了允许在大多数情况下确定络合物的配位数/几何形状的信息。 在这项研究中的配合物被选择，以检查的可靠性的配合物的配位数/几何结构的分配与低对称性和检查的影响，从+II到+III的正式氧化态的变化的光谱。 由于在配体环境的变化对光谱的影响进行检查，和边缘的能量和宽度的边缘被发现与配体环境的平均硬度。 通过使用几对Ni（II/III）isoleptic配合物的光谱，由于氧化态的变化的影响进行检查。 这些化合物表明，在Ni中心的正式氧化态的变化的影响是强烈依赖于存在的配体的性质，与S-供体配体引起的边缘能量比N，O-供体配体较小的位移。 这些趋势表明配体氧化在镍（III）硫醇盐配合物中的作用越来越大。 这些趋势得到了X射线光电子能谱（XPS）研究的证实，该研究表明配体和金属电子结合能具有类似的趋势。 从模型研究中获得的信息用于检查从以C型稳定的Thiocapsa roseopersicina氢化酶样品获得的Ni K边XANES光谱。 该光谱被证明是一致的扭曲的三角双锥几何形状和混合的O，N-和S-供体配体环境，这个生物镍网站。
X-ray absorption near-edge spectra (XANES) are reported for 44 Ni(II) and Ni(III) complexes with N- and/or S-donor ligands. The spectra reveal features associated with 1s --> 3d and 1s --> 4p(z) electronic transitions, whose presence or absence and intensity provide information that allows the coordination number/geometry of the complex to be determined in most cases. The complexes in this study were selected in order to examine the reliability of coordination number/geometry assignments in complexes with low symmetry and to examine the effects on the spectra of a change in formal oxidation state from +II to +III. The effects on the spectra due to changes in the ligand environment are examined, and the edge energy and the breadth of the edge are found to correlate with the average hardness of the ligand environment. The effects on the spectra due to oxidation state changes are examined by using several pairs of Ni(II/III) isoleptic complexes. These compounds reveal that the effects of changes in the formal oxidation state of the Ni center are strongly dependent on the nature of the ligands present, with S-donor ligands giving rise to smaller shifts in edge energy than N,O-donor ligands. These trends are indicative of the increasing role of ligand oxidation in Ni(III) thiolate complexes. These trends are corroborated by X-ray photoelectron spectroscopic (XPS) studies that show a similar trend in both ligand and metal electron binding energies. The information obtained from the model studies is used to examine the Ni K-edge XANES spectrum obtained from a sample of Thiocapsa roseopersicina hydrogenase poised in form C. This spectrum is shown to be consistent with a distorted trigonal-bipyramidal geometry and a mixed O,N- and S-donor ligand environment for this biological Ni site.