Synthesis and Structural Characterization of ... - Jacobs University

Chapter 4
Unpublished Results
of disorder is also found in the previously reported Fe 16 P 8 W 48 . Finally, the BVS of Fe7–O–
Fe8 is ca. 1.70 and of Fe13–O–Fe14 is ca. 1.65, indicating that these oxo bridges are non
protonated. These protonations lead to a total charge of –11 for polyanions 24 and 25. In
addition, terminal aqua ligand molecules coordinate to the lanthanide ions. All terminal W=O
oxygen have lower BVS values than expected (~ 1.5), which is typical for a distorted W=O
bond and does not indicate additional protonation.
Polyanions 24 and 25 are synthesized under mild acidic conditions by interaction of the
precursor P 8 W 48 with Fe(III) and Ln(III) ions in aqueous lithium acetate buffer solution and
in the presence of hydrogen peroxide. We followed the synthetic procedure of the previously
reported Fe 16 P 8 W 48 which has been done based on H 2 O 2 (Bremen method). 10 Polyanions 24
and 25 can also be synthesized in 1 M sodium acetate buffer solution, as confirmed by FTIR.
Besides 24 and 25 we were also able to synthesize the samarium analogue, as confirmed by
FTIR (see Figure 4.6).
Figure 4.6. IR spectra of KLiNaEu-24 and KLiNaGd-25 and samarium analogue measured
on KBr pellets (from bottom to top).
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