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Fig. 3.20
X-ray crystal structures of a 1D polymer through direct coordination of Q[6] mol-
ecules;
a
and
b
tetranuclear cluster uranyl clusters;
c
and
d
carboxylate-bridged dinuclear units
with a chelate ring;
e
and
f
carboxylate-bridged dinuclear units
bonding and formation of a chelate ring is present in only the first isomorphous
group (Fig.
3.20
d, f).
On the basis of experiences in the preparation of tubular coordination poly-
mers involving Q[
n
]s other than Q[6], we introduced transition metal salts, such
as Cd
2
+
or Zn
2
+
salts, into Q[6]-Ln
3
+
-HCl systems [
41
]. From this procedure,
we obtained a series of supramolecular assemblies of lanthanide cations and
Q[6] molecules in the presence of [CdCl
4
]
2
−
or [ZnCl
4
]
2
−
anions, which were
formed in aqueous HCl solution containing the Cd
2
+
or Zn
2
+
salt. The [MCl
4
]
2
−
(M
=
Cd, Zn) anions displayed a “honeycomb effect”, forming honeycomb-like
hollows that could accommodate the 1D supramolecular chains or tubes con-
structed from Ln
3
+
cations and Q[6] molecules through direct coordination.
Considering the similar chemical properties of the lanthanides due to the poor
shielding of nuclear charge by filling of the 4f electron shell, it is reasonable to
expect that the interaction of the various lanthanide cations with Q[6] molecules
give rise to similar coordination features and supramolecular assemblies. Indeed,
the solid-state structures of the obtained complexes, as determined by X-ray crys-
tallography, were all isomorphous in the presence of [CdCl
4
]
2
−
anions. Similar
results could be observed in the Q[6]-Ln
3
+
-[ZnCl
4
]
2
−
systems [
41
].
An overall view of the coordination features and the supramolecular assembly
of the Q[6]/Sm
3
+
complex is given in Fig.
3.21
a as a representative example of
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