Chemistry Reference
In-Depth Information
Fig. 3.28
The common X-ray crystal structures of the Q[7]/Ln
3
+
-based 1D coordination poly-
mers with
a
zigzag and
b
tubular structures in the presence of the [CdCl
4
]
2
−
atoms of the anions and the methine groups on the surface of the Q[
n
] mole-
cules (C-H
methylene
Cl
−
-CdCl
3
). Electrostatic interactions between Ln
3
+
cati-
ons and [CdCl
4
]
2
−
anions could be another important driving force resulting in
the formation of the [CdCl
4
]
2
−
honeycomb in both zigzag and tubular structures
(Fig.
3.29
a-d). Notably, ion-dipole interactions exist between the methine groups
of the Q[7] molecules in the zigzag structure (Fig.
3.29
a, b), which are inclined on
the portals of the neighboring Q[7] molecules (Fig.
3.29
b).
Apart from the Q[7]/Ln
3
+
-based 1D coordination polymers, the uranyl ion
presents an unusual affinity for Q[
n
], and even Q[7]. By dissolving Q[7] and
UO
2
(NO
3
)
2
6H
2
O in excess perrhenic acid under hydrothermal conditions,
Thuéry synthesized two isomeric 1D zigzag polymers in which the uranyl ion
is bound to two carbonyl groups from two neighboring Q[7] ligands. Each Q[7]
molecule acts as a bidentate ligand and coordinates with a uranyl cation at each
portal (Fig.
3.3
a, b) [
50
,
51
]. Moreover, Thuéry first demonstrated a Q[7]/UO
2
2
+
-
based 2D coordination network by dissolving Q[7] and UO
2
(NO
3
)
2
st demon-
strated 6H
2
O in excess sulfuric acid under hydrothermal conditions (Fig.
3.31
a,
b) [
44
]. The crystal structure of the network shows that each Q[7] molecule coor-
dinates with four UO
2
2
+
cations (Fig.
3.31
c), while two sulfate anions coordinate
with two uranyl cations and form a pentagonal bipyramidal uranium environment
(Fig.
3.31
d). The combined coordination of Q[7] molecules and uranyl/sulfate
units leads to the formation of novel Q[7]-based coordination networks.
In the presence of CsNO
3
, which may function as a structure inducer, the
Q[7]-UO
2
(NO
3
)
2
system may also yield a 2D coordination network under
hydrothermal conditions (Fig.
3.32
a) [
51
]. Similarly, each Q[7] molecule
coordinates with four UO
2
2
+
cations, while two uranyl cations form a planar
−
Search WWH ::
Custom Search