The use of EXAFS spectroscopy to determine metal coordination in solution

The availability of 3rd generation synchrotrons in Europe has strongly enhanced the use of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy to determine the structure of systems that are not accessible with X-ray diffraction or NMR techniques alone. This presentation intends to demonstrate how the combination of EXAFS, UV-Vis and XRD provide insight in the coordination of solution species. The combination of EXAFS and UV-Vis is often successful, because both techniques are sensitive in the same concentration range. Statistical approaches like factor analysis allow the analysis of large series of titration data providing the coordination of the solution species as well as species distribution functions. At the other hand, XRD is nowadays a standard technique to reveal atomic structures of single crystals. However, there is often no link between structures in solution and its solid state structure. The capability of EXAFS to detect both, the near-order structure in solution and solid state, provides the unique opportunity to follow structural modifications during the crystallization process and to use the solid state structure or its modifications to reveal the coordination of metal complexes in solution.