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(C-HO
=
C, another type of pseudo-hydrogen bonding) is in the range of 3.076-
3.242 Å. Using a similar strategy, ZnCl
2
, CuCl
2
, and CoCl
2
were introduced into
the Sr
2
+
-Q[8]-HCl systems to give isomorphous compounds that exhibit similar
coordination features and supramolecular assemblies.
We have introduced the honeycomb effect of the ([M
trans
Cl
4
]
2
−
anions, which
form honeycomb-shaped cells via ion-dipole interactions and C-HCl interac-
tions, as well as tubular Q[
n
]/M
n
+
coordination polymers that fill the honeycomb
cells. M
trans
in the ([M
trans
Cl
4
]
2
−
anions could be Cd, Zn, Cu, Co, Ni, or others;
the Q[
n
]s in the tubular Q[
n
]/M
n
+
coordination polymers include Q[6], Q[7], and
Q[8]. The metal in the tubular Q[
n
]/M
n
+
coordination polymers could be a lantha-
nide or alkaline earth metal. The process is summarized in Scheme
3.5
[
56
].
We have observed various 2D coordination polymers involving Q[5]s, Q[6]s,
and Q[7]. Herein, we introduce the 2D-network coordination polymers involv-
ing Q[8]. Thuéry first demonstrated a Q[8]/UO
2cluster
-based 2D network coordi-
nation polymer by chance when he simply mixed Q[6] with UO
2
(NO
3
)
2
6H
2
O
in sulfuric acid in a tightly closed glass vessel under hydrothermal conditions.
The obtained product probably includes Q[8] as an impurity in Q[6]. Figure
3.35
shows an overall view of the Q[8]/UO
2cluster
-based 2D-network coordination poly-
mer, which is the third example of metal-coordinated Q[8] after the Bi(III) [
57
]
and Sr(II) [
58
] complexes, which are the first known Q[8]-based 2D-network
coordination polymers. Each Q[8] molecule is thus bound to four uranium atoms
through two centrosymmetrically related groups of two adjacent glycoluril units,
Scheme 3.5
Representation of the honeycomb effect derived from the cucurbit[
n
]urils-based
coordination chemistry. Adapted from Ref. [
56
] with permission from The Royal Society of
Chemistry
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