Hydrated structures and dehydration processes of lanthanoid(III) chloranilates studied by EXAFS

The local structures of lanthanoid(III) chloranilate complexes of Pr(III), Nd(III), Tb(III) and Er(III) have been studied by EXAFS (extended X-ray abs orption fine structure). Hydrated structures of the lanthanoid(III) ions in these complexes have been investigated with respect to their coordination numbers and interatomic distances. Six or four water molecules coordinate t o the lanthanoid(III) ion of Pr(III) or Nd(III), respectively, just after p reparation of the complexes. The temperature dependence of the first coordi nated structures has been studied in order to reveal the behavior of the co ordinated water molecules in dehydration process. The coordination number a round the central lanthanoid(III) ion decreases stepwise as temperature inc reases, depending on the type of central lanthanoid(III) ion present. The i nteratomic distance between the central lanthanoid(III) ion and oxygen atom s in the first shell decreases, accompanying the decrease of the coordinati on numbers. A parameter representing proportion shows the reduction of inte ratomic distance as one coordinated water molecule removes from the central ion, depending on the type of lanthanoid(III) ions. (C) 1999 Elsevier Scie nce Ltd. All rights reserved.