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Fig. 2.20
X-ray crystal structures of tetranuclear lanthanide aqua hydroxo-Q[6] sandwich com-
plexes:
a
representative tetranuclear lanthanide aqua hydroxo core; typical sandwich complexes
in which
b
Ln
=
Gd [
55
], Ho [
55
], Er [
55
,
56
], Yb [
56
];
c
Ln
=
Dy [
57
], Ho [
57
], Er [
57
];
d
Ln
=
La [
57
];
e
Ln
=
Pr [
56
,
57
], Nd [
56
]; and
f
Ln
=
La [
57
], Pr [
57
], Dy [
57
]; the tetrahedral
Ag
+
centers are shown above and below the
top
and
bottom
portals of the Q[6] sandwich structure
linked via coordination of their nitrogen atoms to Ag
+
ions to yield repeating units
of the type shown in Fig.
2.20
f.
Although Fedin et al. originally focused on the preparation of polynuclear lan-
thanide complexes, the approaches that they adopted greatly aided the develop-
ments in Q[
n
]-based host-guest coordination chemistry.
Since 2008, Thuéry have synthesized numerous Q[6]-based complexes with
lanthanides and actinides in various media, such as neutral aqueous solution,
nitric acid, sulfuric acid, formic acid, and perrhenic acid. These reactions have
been carried out in the presence of various species, which could behave as struc-
tural inducers: examples include sebacic acid, L-(
+
)-tartaric acid, citric acid, and
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