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Fig. 3.9 The structural characteristics of the trigonal-planar branch constructed from DMeQ[5]
molecules and K + ions
the interplay between alkyl substituents of neighboring Q[5]s was expected to lead
to novel solid-state structures or metal-organic frameworks (MOFs) with unusual
structures, including bracelet motif structures (Scheme 3.3 ) [ 20 ].
Our recent work revealed that SQ[5]s generally coordinate directly with
metal ions to form various SQ[5]-based MOFs with unusual structures. In such
cases, a common structural motif, the trigonal-planar branching unit, is observed
(Fig. 3.9 ). As mentioned, the dihedral angles between the junction plane and
the center junction plane could indicate the construction of 2D networks or 3D
frameworks through SQ[5]/M n + direct coordination [ 18 - 20 ]. When the dihe-
drals between any two K + -based junction planes have the same angle of 70.53°
in the trigonal-planar branch, the trigonal-planar branches fuse into 10-membered
SQ[5] bracelets, but the six-membered SQ[5]s can further fuse into 2D network
coordination polymers, and which then fuse into 3D frameworks. Remarkably,
two identical but independent 3D infinite frameworks are generated, which are
mechanically linked through catenation. The resulting 3D frameworks are there-
fore composed of catenated, multifused 10-membered bracelets incorporating
potassium ions that link adjacent SQ[5] units through simultaneous coordina-
tion to their portal oxygens. Figure 3.10 a-c shows three alkyl-substituted Q[5]s
and their supramolecular assemblies through direct coordination with potassium
cations.
We closely inspect the trigonal-planar branch constructed from three 1,2,4-
HMeQ[5] molecules (Fig. 3.10 d). Two different K + ions (K1 and K2), located at
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