Correlation between local structure and molar ratio of Au (III) complexes in aqueous solution: An XAS investigation |
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| Authors: | Xing Chen Wangsheng Chu Dongliang Chen Zhonghua Wu A Marcelli Ziyu Wu |
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| Institution: | aNational Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China;bBeijing Synchrotron Radiation Facility, Institute of High Energy Physics, CAS, 100049 Beijing, China;cLaboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, 00044 Frascati, Italy;dTheoretical Physics Center for Science Facilities, Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | The local and geometrical structure around gold (III) e.g., Au3+ ions in aqueous solution with different OH−/Cl− molar ratios, has been investigated by X-ray absorption spectroscopy (XAS). X-ray absorption near-edge structure (XANES) spectra of AuCln(OH)4−n]− solutions have been calculated and the multiple-scattering spectral features have been attributed to Cl d-states, axial water molecules and the replacement of Cl− ligands by OH− ligands. A square–planar geometry for AuCln(OH)4−n]− with two axial water molecules has been identified. Moreover, a spectral correlation between XANES features and the type of planar atoms has been identified. By extended X-ray absorption fine structure spectra (EXAFS), the planar Au bond distances in the solutions have also been determined, e.g., 2.28 Å for Au–Cl and 1.98 Å for Au–O, respectively. The same EXAFS analysis provides evidence that the peak at about 4.0 Å in solutions with the lowest OH−/Cl− molar ratio arises from collinear Cl–Au–Cl multiple-scattering contributions. For the first time, a complete detailed reconstruction of the hydration structure of an Au ion at different pH values has been achieved. |
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| Keywords: | Au3+ OH− /Cl− molar ratio The local structure XANES EXAFS |
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