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Scheme 3.1
Assembly of 1D (
a
) and 2D (
b
) catenated frameworks based on metal-ion-linked
cucurbiturils
differences that lead to the formation of different six-membered rings with differ-
ent geometric patterns. These differences could in turn affect the structural con-
formation of the formed 2D networks and the superimposition of the networks in
the corresponding compounds. We closely inspect the trigonal-planar branch con-
structed from three DMeQ[5] moieties (Figs.
3.8
b and
3.9
). Both portals of each
DMeQ[5] molecule in the branch are fully covered by potassium cations through
direct coordination. Moreover, each capping K
+
ion is coordinated to a portal car-
bonyl oxygen of a neighboring DMeQ[5] in the trigonal-planar branch. Thus, three
capping potassium cations form a junction link of three DMeQ[5] molecules and
lead to the formation of the trigonal-planar branch. At the respective portals of the
DMeQ[5] molecule, one can see four junctions of three capping K
+
, which reside
in the same chemical environment. In other words, the four junctions of three cap-
ping K
+
are identical. The two adjacent DMeQ[5] portals are mutually offset in
the trigonal-planar branch, at offset angles of 61.79°, 62.13°, and 59.03°, as shown
in Fig.
3.9
. There are four identical junctions linked by three K
+
ions (K1, K2,
and K3) in the trigonal-planar branch. The dihedral angles between the junction
plane and the center junction plane are 6.75° for ∠S0S1, 32.12° for ∠S0S2, and
32.12° for ∠S0S3. The two junction planes S2 and S3 are clearly parallel in the
trigonal-planar branch, with a gap (
d
S2-S3
) of 5.534 Å. The dihedral angle seems
to be an important parameter that could indicate the construction of 2D networks
or 3D frameworks through SQ[5]/M
n
+
coordination [
19
].
Much attention in supramolecular chemistry has been focused on the design and
synthesis of interlocked molecules, such as rotaxanes, catenanes, and molecular
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