Persson Ingmar, Lundberg Daniel, Bajnóczi Éva G, Klementiev Konstantin, Just Justus, Sigfridsson Clauss Kajsa G V
Department of Molecular Sciences, Swedish University of Agricultural Sciences, P.O. Box 7015, SE-750 07 Uppsala, Sweden.
MAX IV Laboratory, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden.
Inorg Chem. 2020 Jul 20;59(14):9538-9550. doi: 10.1021/acs.inorgchem.0c00403. Epub 2020 Jul 2.
The structures of the solvated copper(II) ion in water and nine organic oxygen donor solvents with similar electron-pair donor ability, but with different space-demanding properties at coordination, have been studied by EXAFS. -Dimethylpropyleneurea and -tetramethylurea are sufficiently space demanding at coordination to make the axial positions not accessible, resulting in square-planar copper(II) solvate complexes with an intense green color. The mean Cu-O bond distances in these two solvate complexes are 1.939(3) and 1.935(3) Å, respectively. The best fits of the remaining solvates, which are light blue in different hues, are obtained with a Jahn-Teller distorted-octahedral model consisting of four strongly bound solvent molecules in the equatorial positions at 1.96(2) Å and two in the axial positions but with different Cu-O bond distances: ca. 2.15 and 2.32 Å. This is in agreement with observations in solid-state structures of compounds containing hexaaquacopper(II) complexes crystallizing in noncentrosymmetric space groups and all reported crystal structures containing a [Cu(HO)(O-ligand)] complex with Jahn-Teller distortion. Such a structure is in agreement with previous EPR and EXAFS studies proving the hydrated copper(II) ion to be a noncentrosymmetric complex in aqueous solution. The refinements of the EXAFS data of the solids Cu(HO), Cu(HO), [Cu(HO)]SiF, Cu(NO)·2.5HO, and CuSO·5HO gave Cu-O bond distances significantly different from those reported in the crystallographic studies but similar to the configuration and bond distances in the hydrated copper(II) ion in aqueous solution. This may depend on whether the orientation of the axial positions is random in one or three dimensions, giving a mean structure of the solid with symmetry higher than that of the individual complexes. This study presents the very first experimental data from the new X-ray absorption spectroscopy beamline Balder at the MAX IV synchrotron radiation facility in Lund, Sweden, as well as the utilized properties of the beamline.
利用扩展X射线吸收精细结构谱（EXAFS）研究了水合铜（II）离子在水中以及九种具有相似电子对给体能力、但配位时空间需求特性不同的有机氧给体溶剂中的结构。N,N-二甲基丙撑脲和N,N,N',N'-四甲基脲在配位时空间需求足够大，使得轴向位置无法被占据，从而形成具有强烈绿色的平面正方形铜（II）溶剂化物配合物。这两种溶剂化物配合物中铜-氧键的平均键长分别为1.939(3) Å和1.935(3) Å。其余呈不同色调浅蓝色的溶剂化物，其最佳拟合结果是采用一个 Jahn-Teller 畸变八面体模型，该模型由四个在赤道位置以1.96(2) Å键合的强配位溶剂分子和两个在轴向位置但铜-氧键长不同的溶剂分子组成：约为2.15 Å和2.32 Å。这与在非中心对称空间群中结晶的含六水合铜（II）配合物的化合物固态结构观测结果以及所有报道的含[Cu(HO)(O-配体)]且具有 Jahn-Teller 畸变的晶体结构一致。这种结构与之前的电子顺磁共振（EPR）和EXAFS研究结果相符，这些研究证明水合铜（II）离子在水溶液中是一种非中心对称配合物。对固体Cu(HO)、Cu(HO)、[Cu(HO)]SiF、Cu(NO)·2.5HO和CuSO·5HO的EXAFS数据进行精修，得到的铜-氧键长与晶体学研究报道的显著不同，但与水溶液中水合铜（II）离子的构型和键长相似。这可能取决于轴向位置在一维或三维中是否随机取向，从而使固体的平均结构对称性高于单个配合物。本研究展示了来自瑞典隆德MAX IV同步辐射设施新的X射线吸收光谱光束线Balder的首批实验数据，以及该光束线的应用特性。
