11 Layered Hydrogen-Bonded Organic …
203
on shape-fitted docking strategy with hexaazatriphenylene (HAT) derivatives 6a, b
[32, 33, 41]. Stoddart and co-workers reported that triptycene derivative 7 provided
interpenetration polymorphs of H-bonded networks [39].
It is remarkable that reported building blocks contain carboxyphenyl groups
instead of carboxy groups. This is probably because such building-block molecules
can easily synthesized by metal-catalyzed cross-coupling reactions between
aryl groups such as Suzuki–Miyaura reaction [49]. Moreover, introduction of
carboxyphenyl groups into π-conjugated skeleton improves solubility of the
molecule into solvents compared with those directly bonded by carboxy groups
[50, 51]. The phenylene group also acts as a spacer to generate pores [52]. However,
systematic construction of carboxylic-acid-based HOFs is still challenging.
In connection with this, we have proposed that C 3 -symmetric π-conjugated
building blocks (C 3 PIs) possessing three o-bis(4-carboxyphenyl)benzene moieties
in periphery of the core can systematically provide isostructural H-bonded hexagonal networks (H-HexNets) with multiple void spaces, and that the HexNets are
stacked without interpenetration to give porous layered assembly of H-HexNets
(LA-H-HexNets). This working hypothesis to achieve formation of H-HexNet-based
layered HOF is summarized in Fig. 11.4. C 3 -symmetric, rigid, planar cores with sides
of two different lengths are applied for the central part of C 3 PIs. Such C 3 PIs enable
the formation of a planar 2D H-HexNet motif with multivoid spaces. Moreover, the
size and shape of the void can be varied by changing the side length of the C 3 PIs. The
peripheral o-bis(4-carboxyphenyl)benzene moieties can form a H-bonded triangular
porous motif, so-called phenylene triangle (PhT) motif to network the C 3 PI. The PhT
motif was first observed in a crystal of hexakis(4-carboxyphenyl)benzene reported
by Kobayashi and co-workers in 2000 [53].
Fig. 11.4 Schematic representation for construction of layered assembly of hydrogen-boned hexagonal networks (LA-H-HexNet) with planar C 3 -symmetric π-conjugated molecules (C 3 PIs) via
formation of a cyclic hydrogen-bonded motifs, so-called phenylene triangle (PhT) motif
203
on shape-fitted docking strategy with hexaazatriphenylene (HAT) derivatives 6a, b
[32, 33, 41]. Stoddart and co-workers reported that triptycene derivative 7 provided
interpenetration polymorphs of H-bonded networks [39].
It is remarkable that reported building blocks contain carboxyphenyl groups
instead of carboxy groups. This is probably because such building-block molecules
can easily synthesized by metal-catalyzed cross-coupling reactions between
aryl groups such as Suzuki–Miyaura reaction [49]. Moreover, introduction of
carboxyphenyl groups into π-conjugated skeleton improves solubility of the
molecule into solvents compared with those directly bonded by carboxy groups
[50, 51]. The phenylene group also acts as a spacer to generate pores [52]. However,
systematic construction of carboxylic-acid-based HOFs is still challenging.
In connection with this, we have proposed that C 3 -symmetric π-conjugated
building blocks (C 3 PIs) possessing three o-bis(4-carboxyphenyl)benzene moieties
in periphery of the core can systematically provide isostructural H-bonded hexagonal networks (H-HexNets) with multiple void spaces, and that the HexNets are
stacked without interpenetration to give porous layered assembly of H-HexNets
(LA-H-HexNets). This working hypothesis to achieve formation of H-HexNet-based
layered HOF is summarized in Fig. 11.4. C 3 -symmetric, rigid, planar cores with sides
of two different lengths are applied for the central part of C 3 PIs. Such C 3 PIs enable
the formation of a planar 2D H-HexNet motif with multivoid spaces. Moreover, the
size and shape of the void can be varied by changing the side length of the C 3 PIs. The
peripheral o-bis(4-carboxyphenyl)benzene moieties can form a H-bonded triangular
porous motif, so-called phenylene triangle (PhT) motif to network the C 3 PI. The PhT
motif was first observed in a crystal of hexakis(4-carboxyphenyl)benzene reported
by Kobayashi and co-workers in 2000 [53].
Fig. 11.4 Schematic representation for construction of layered assembly of hydrogen-boned hexagonal networks (LA-H-HexNet) with planar C 3 -symmetric π-conjugated molecules (C 3 PIs) via
formation of a cyclic hydrogen-bonded motifs, so-called phenylene triangle (PhT) motif