Chemistry Reference
In-Depth Information
A
B
C
D
E
F
G
H
I
J
J'
J''
Scheme 2 Various molecular networks consisting of aromatic units (
ellipsoids
) and linkers (
lines
or curves
)
2.4 Classification of Aromatic Networks
The modes of network structures can be classified according to theories in related
research fields. The graph theory studies structures of graphs consisting of nodes
and edges (links), which are equivalent to arene units and linkers, respectively, in
aromatic networks [
23
]. In the field of network topology, topologies are classified
into several basic types such as ring, mesh, star, and hybrid. The features of typical
networks with at least one ring structure (Scheme
2
) are briefly discussed with the
aid of those theories.
Aromatic networks are chiefly characterized by the numbers of arene units and
linkers and then by the mode of linkage. Network A with two arene units and two
linkers is the simplest; it represents the structure of cyclophanes, which are funda-
mental cyclic compounds in aromatic chemistry. Two arene units can be connected
by three or more linkers to form multiply bridged cyclophanes, as illustrated in
network B. Three arene units are connected by three linkers in cyclic form C,orby
four linkers to form multi-layer architecture D. Cyclic structure E with four arene
units and four linkers is a typical ring-type network and called a simple graph. In
contrast, every pair of arene units is connected in network F by a linker, and this is
called a fully connected mesh or a complete graph.
