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planar arrangement with an average Cl- • -O distance of
3.01 A creating a two-dimensional array (Figure 89). Hydrogen bonding
between layers generates a three-dimensional network with 4.6 x 3.4 A
wide channels (Figure 90).
41 / Porphyrin Materials Chemistry
Figure 66. Helical packing in Zn[T(p-CI)PP]-C6H2NO;,. Reprinted with
permission from Goldberg, I.; Krupitsky, H.; Stein, Z.; Hsiou, Y.;
Strouse, Ñ. E. Supramol. Chem. 1995, 4, 203. (c) 1995 Gordon and Breach
When the hydroxyl substituents are simply changed from Ihe meta- to
the ortho-phenyl positions, an essentially two-dimensional layered
material results. The peripheral hydroxyl groups of H2|T(2',(V-DHP)PJ -
4EtOAc induce a slight ruffling of the porphyrin macrocyclic rings and
show strong directional hydrogen bonding (Figure 91). Channels 3.0 x 3.6
A wide were formed by the packing of the layers (Figure 92). A similar
packing motif was observed for (he Zn(II) metalloporphyrin species.1''1
3. Metal-lon Coordination Network Materials
In the last decade significant progress toward the rational construction
of three-dimensional solids constructed from metal cations and organic
molecules has been described.1'71's Of particular interest have been
metal-organic coordination networks possessing nanoscale pores.I W Metal-
ligand interactions are often quite strong and should therefore provide a
more robust framework than those based on van der Waals, hydrogen bonding
or n-n interactions.
Goldberg and coworkers have reported a number of inclusion compounds
utilizing coordination of substituted
letraphenylporphyrins. Porphyrinic-inclusion compounds of
5,10,15,20-tetra(4-pyridyl(porphyrin. H2(TPyP), exhibited two general
motifs.140 Crystallization of the Zn(TPyP) complex resulted in a geometry
featuring "zigzag" polymer chains in which the central Zn(ll) ion is
axially ligated by pyridyl substituent from an adjacent porphyrin (Figure
93). A similar arrangement was observed for inclusion compounds of
aromatic solvents such as aniline (Figure 94). Only one pyridyl moiety
per porphyrin building block coordinates to another porphyrin, thereby
limiting ligand-metal interactions to one-dimensional polymeric chains.
The guest species is located in a cavity adjacent to the pyridyl
substituent tram- to the pyridyl axially ligating the metal center of an
adjacent porphyrin in the zigzag chain.
A second motif encountered in tetrapyridylporphyrin systems is
typified by inclusion compounds with wet methanol and water that produce
three-dimensional coordination polymers. 7>w?5-pyridyl substituents on a
Zn(TPyP) were observed to axially ligate the metal centers of adjacent
porphyrin moieties generating a polymeric chain in one dimension. Cross-
linking in a second dimension occurs when the original porphyrin molecule
is coordinated by two pyridyl moieties from two additional porphyrin
Figure 67. Herring-bone packing arrangement of Zn(T(p-CI)PP),C7H7CI.
Reprinted with permission from Krupitsky, H.; Stein, Z.; Goldberg, I. /.
Inclusion Phenom. Mol. Recognit. Chem. 1995, 20, 211.
(Figure 95). The two remaining pyridyl groups participate in hydrogen
bonding with included water molecules. An intricate three-dimensional
framework results (Figure 96).
For inclusion solids of 5,10,15,20-tetra(4-cyano)phenyl-porphyrin,
H2[T(p-CN)PP], one of the four structural motifs encountered by Goldberg
involved ligand to metal interactions.131 Two-dimensional coordination
networks similar to those observed for Zn(TPyP) materials were found in
Zn[T(p-CN)PPJ-2CfiH5N02 (nitrobenzene), Zn[T(p-CN)-PP]-CHC13 (chloroform)
and Zn[T(p-CN)PP] • C7H80 (anisole) materials (Figure 97). The guest
species intercalate between the porphyrin layers (Figure 98).
Attempting to mimic the topology of the PtS structure, Robson and
coworkers explored metal-to-ligand coordina-tive bonding as a means to
build more robust porphyrinic materials. They reported a structure in
which Pd(TPyP) molecules are interconnected by Cd(II) centers.141 Each
porphyrin is coordinated by two frans-pyridyl donor porphyrin molecules
and by two cis donor porphyrin molecules (Figure 99). The overall neutral
framework [Pd(TPyP) • Cd(N03)2 • 8.6H20] features infinite interwoven
layers of the porphyrin network.
In subsequent work, Robson and coworkers142 reported three-dimensional
network solids using the copper por-
41 / Porphyrin Materials Chemistry
Figure 68. Corrugated layer arrangement in Zn(T(p-Br)PP)-4C6H7N.
Reprinted with permission from Dastidar, P.; Krupitsky, H.; Stein, Z.;
Goldberg, I. j. Inclusion Phenom. Mol. Recognit. Chem. 1996, 24, 241.
phyrin complexes of 5,10,15,20-tetra-4'-pyridylporphyrin, Cu(TPyP), and
5,10,15,20-tetra-4'-cyanophenylpqrphyrin, Cu(TCNPP). Large extended
channels (10-20 A) were observed in which tetrahedral Cu(I) ions (as
opposed to the square planar Cu(II) ions bound to the center of the