198 Topics in Current Chemistry Editorial Board: A. de Meijere KN ...

Functional Organic Zeolite Analogues 133
and prospects associated therewith. The dynamic nature, especially the catalysis,
is concerned, among others, with the author’s own work. Several proposals will be
made, whose generalisation awaits further testing in other systems.
2
Static Aspects
2.1
Molecular Networks Using Supramolecular Building Blocks
Porosity may be generated in crystals when the awkward shape of constituent
molecules prohibits their close packing. Examples are such hosts as 1–4. They
are all rigid and have bulky substituents (1 [18] and 2 [19]), inclined planes
(3 [20, 21]) [22] or bent surfaces (4 [23]) with or without polar groups capable of
intermolecular hydrogen bonding. They all form lattice inclusion compounds.
Indeed, the tetraarylporphyrins 3 and bile acid derivatives 4 constitute the most
comprehensively studied clathrate hosts. While general packing modes and
lattice patterns of the hosts are well conserved, the guest molecules are included
in open voids and the guest-binding modes are often guest-dependent, especially
when host-guest hydrogen-bonding comes into play [24].
1 2
3 4
In the context of zeolite analogues, we are concerned about closed voids,
which are more or less designable and hopefully modifiable systematically and
are less sensitive to the included guests. A common strategy is to network rigid
molecular building blocks [25] or tectons [26] by using directional intermolecular
interactions such as hydrogen bonding, metal coordination, and others
(e.g. X◊◊◊X, CN◊◊◊H, CN◊◊◊X, and CX◊◊◊p interactions; X=halogen) [27] as supramolecular
synthons [28] or modules [29]. A robust n-dimensional (nD) module
which competes favourably with van der Waals packing forces would reduce the
crystal engineering problem from 3D to (3–n)D in the resulting nD-controlled
material [30].