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Systematic Study of the Interaction Between VIV Centres and LnIII Ions in Well Defined {V2IVLnIII}{AsIIIW9O33}2 Sandwich-Type Clusters: Part 2
Ist Teil von
Journal of cluster science, 2013-12, Vol.24 (4), p.979-988
Ort / Verlag
Boston: Springer US
Erscheinungsjahr
2013
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
The gadolinium (Gd) member of a new type of heteropolytungstates that contain one lanthanide and two transition metal ions in a triangular arrangement is reported. The compound NaK
6
Gd
0.33
[((VO)
2
Gd(H
2
O)
4
K
2
(H
2
O)
2
(Na)(H
2
O)
2
)(α-B-AsW
9
O
33
)
2
]·24H
2
O (
1
) was prepared from acidified aqueous solutions of Na
2
WO
4
·2H
2
O, As
2
O
3
and VOSO
4
·5H
2
O to which Gd
3+
ions were added. The single crystal X-ray structure analysis (monoclinic, space group
P
2
1
/
m
) shows that the anion consists of two [α-B-As
III
W
9
O
33
]
9−
trilacunary Keggin-type units linked by two VO
2+
, one Gd
3+
as well as weakly by two K
+
and one Na
+
ions, resulting in a sandwich-type structure with idealized
C
2v
symmetry. The problem of positioning crystal lattice and special polyoxometalate sites with different cations is discussed also in connection with supramolecular chemistry aspects and as an option for further research. A fit of the magnetic susceptibility yielded exchange coupling constants of
J
VV
= −2.55 cm
−1
(anti-ferromagnetic) between the vanadium ions and
J
GdV
= 0.6 cm
−1
(ferromagnetic) between the Gd and each of the two vanadium ions. The complete magnetochemical analysis also revealed a partial occupancy of the Na
+
sites in the counter-cation–water system by Gd
3+
ions (0.33 Gd
3+
ions in total).