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44
45
Scheme 15 Macrocyclic cage networks with benzene units and acetylene linkers
cage molecules have a microporous packing. Triptycene units were also
incorporated into calixarene macrocycles, and some derivatives could accommo-
date fullerenes C
60
and C
70
in their expanded cavity [
91
,
92
].
5.2 Cage Networks with Coordination Linkers
A variety of 3D cage networks can be constructed by spontaneous self-assembly of
rationally designed multitopic ligands with metal ions. Fujita et al. reported the
selective formation of octahedron-shaped M
6
L
4
complex 46 (M: metal, L: ligand)
from tris(4-pyridyl)triazine 47 and
cis
-coordinated Pd(II) complex in water
(Scheme
16
)[
93
]. The framework of 46 is ca. 20
˚
in diameter and this large
cavity accommodates various guest molecules. The cavity size in the octahedral
framework was increased by using large ligands with extra linkers between the
4-pyridyl groups and the triazine core. The shape and size of 3D networks can be
modified by designing the ligand in terms of orientation, direction, and number of
coordination sites [
94
]. According to these empirical predictions, a giant M
24
L
48
polyhedral cage was synthesized from 2,5-bis(4-pyridyl)pyrrole ligand [
95
]. The
cage cavities of these coordination networks are applicable to containers of guest
molecules, reaction vessels, and generation of novel molecular species [
96
-
98
].
The combination of multitopic ligands and Pt(II)-containing molecules sponta-
neously generates various 3D cages depending on the geometry of building units
[
21
]. The treatment of anthracene clip 49 with terminal
trans
-coordinated Pt(II)
atoms and planar tritopic ligand 50 gave 3D cage network 48 with a trigonal
prismatic frameworks (Scheme
17
)[
99
]. The formation of molecular prisms was
confirmed by ESI mass spectra. The use of a tripod donor instead of the trigonal
