Crystal structures of lanthanide terephthalate tetrahydrate, R2(C8H4O4)3(H2O)4, R = La–Er

Abstract

The crystal structures of 11 lanthanide terephthalate tetrahydrates have been refined using laboratory X-ray powder diffraction data and optimized using density functional techniques. The lattice parameters and R–O bonds exhibit expected trends based on the cation size. The R–O bond distances in the Rietveld-refined structures are similar. However, in the density functional theory (DFT)-optimized structures, the bond distances break into two distinct groups, longer and shorter R–O bonds. This indicates that the bond distance restraints imposed upon the refined structures may have a greater impact than is expected from their weights. The aromatic carboxyl groups were not completely planar, but it is known that the carboxyl groups can rotate to accommodate hydrogen bonding and coordination to the metal. Both water molecules coordinated to the lanthanides act as hydrogen bond donors, but only one of the three unique carboxyl groups acts as an acceptor.