EXAFS characterisation of metal bonding in highly luminescent, UV stable, water-soluble and biocompatible lanthanide complexes

A Kalyakina,Y Zubavichus,N Kuzmina,V Utochnikova,S Bräse,A Trigub

doi:10.1088/1742-6596/712/1/012137

Abstract

The combination of X-ray diffraction with EXAFS was employed to assess the coordination environment of lanthanide complexes in solutions. This method is based on the assumption that the local structure of lanthanide complexes in solution combines elements of the crystal structure of the complex in the solid state (single- or polycrystalline) and the elements of the local structure of a lanthanide salt, completely dissociated in the solvent (usually chlorides). The success of this approach is demonstrated with the lanthanide (III) 2,3,4,5,6-pentafluorobenzoate complexes, where the local structure in aqueous and methanol solutions were estimated. Moreover, the dissociation degree of the complexes in aqueous and methanol solutions was evaluated.

Highlights

Over the past decades EXAFS has been widely used for structural analyses of various compounds and materials, when X-ray diffraction methods are not applicable or their application is relatively limited
To estimate the composition of coordination sphere around the lanthanide ion, EXAFS spectra were obtained for aqueous (H2O-Ln) and methanol solutions (CH3OH-Ln)
EXAFS spectroscopy allows us to distinguish them by the appearance of the Ln⋯C scattering path in the second shell

Summary

Introduction

Over the past decades EXAFS has been widely used for structural analyses of various compounds and materials, when X-ray diffraction methods are not applicable or their application is relatively limited. The main idea underpinning the present study is the finding that pfb ligands possess different coordination modes depending on the metal used, and even complexes with the same metal can give rise to different molecular structures. To estimate the composition of coordination sphere around the lanthanide ion, EXAFS spectra were obtained for aqueous (H2O-Ln) and methanol solutions (CH3OH-Ln).

Results

Conclusion