Synthesis and Structural Characterization of ... - Jacobs University

Chapter 1
Introduction
ligand for one of the cerium ions, and its presence during the synthesis is crucial since
replacement of HCl (aq.) by HNO 3(aq.) as acidification reagent and of KCl (aq.) by KNO 3(aq.) as
crystallization agent did not result in the desired product.
Figure 1.12 Combined polyhedral/ball-and-stick representation of [H 6 Ce 2 (H 2 O)ClW 15 O 54 ] 7− .
Red octahedra: WO 6 , blue balls: cerium, red ball: oxygen, pink ball: H 2 O, yellow ball:
chlorine.
The polyanion [H 6 Ce 2 (H 2 O)ClW 15 O 54 ] 7− consists of an assembly of 15 WO 6 octahedra
stabilized by two nonacoordinate cerium(III) ions by W–O–Ce bridges resulting in a
polyanion with idealized C 3 symmetry. The isopolyanion part corresponds to three {W 5 O 18 }
units, each comprising three edge-shared and two corner-shared WO 6 octahedra. These three
{W 5 O 18 } units are joined to form a 15-membered ring which is capped on each side by a
stabilizing cerium(III) ion. Six protons were also identified to be delocalized on the
isopolyanion. Each cerium(III) ion exhibits a highly distorted, tri-capped trigonal-prismatic
coordination, with eight oxygen donors from the isopolyanion units. One of the cerium ions
has a terminal aqua ligand and the other a chloro ligand. This polyanion was investigated in
solution by UV/Vis spectroscopy, photoluminescence and cyclic voltammetry studies.
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