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The porphyrin handbook - Kadish K.M.

Kadish K.M. The porphyrin handbook - Academic press, 2000. - 368 p.
Download (direct link): kadishsmishgulilard2000.djvu
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omitted for clarity.135
Figure 93. Crystal packing in Zn(TPyP) coordination polymers. Reprinted
with permission from Krupitsky, H.; Stein, Z.; Goldberg, I. /. Inclusion.
Phenom. Mol. Recognit. Chem. 1994, 18, 177.
ing materials parallels the interest in synthetic metals. In a sense, the
copper-oxide high-temperature superconductors (e.g., YBa2Cu307_x with Tc.
~95K) are two-dimensional coordination polymers, but we will not discuss
them further
here.176-178

Porphyrins constitute a versatile building block for the preparation of
conductive polymers. The large n system of
porphyrins and metalloporphyrins yields a HOMO and LUMO which are
generally separated by only 2 eV.179 This gap can be narrowed via
polymerization or additional conjugation, leading to interesting
conductivity possibilities. In addition to conduction through the n
system, metal-metal conductivity is possible within a chain of
metalloporphyrins. Because porphyrins are able to coordinate a
104
Chou et al.
Figure 94. Zigzag packing in 2n(TPyP)-C6H7N. Reprinted with permission
from Krupitsky, H.; Stein, 2.; Goldberg, I. /. Inclusion. Phenom. Mol.
Recognit. Chem. 1994, 18, 177.
Figure 95. Three-dimensional interporphyrin bonding observed in Zn(TPyP)
3H20. Reprinted with permission from Krupitsky, H.; Stein, 2.;
Goldberg, I. j. Inclusion. Phenom. Mol. Recognit. Chem. 1994, 18, 177.
41 / Porphyrin Materials Chemistry
105
Figure 96. Crystal structure of Zn(TPyP)-CH30H-2H?0. The marked hexagons
indicate hydrogen-bonding interactions between six water molecules and
pyridyl groups of porphyrins in adjacent unit cells. Reprinted with
permission from Krupitsky, H.; Stein, Z.; Goldberg. I. j. Inclusion.
Phenom. Mol. Recognit. Chem. 1994, 18, 177.
wide range of metals, conductivity is readily tunable in these eases.
a. Sliisli Kebab Porphyrin Polymers
The "shish kebab" approachlsluls? yields a class of coordination
polymers based on stacked macrocyclic metal complexes (Figure 1 15).
Here, macrocyclic complexes are linked together by axial coordination of
bridging ligands. Until recently, shish kebab polymers with bridging
ligands larger than a single atom were rare. |Sni4(OEP))-
(pimelate)K and |Zr(OEP))(succinate)] 4 were two early examples.IM In the
late seventies, Hanack ct al. started to prepare a large family of such
polymers employing phthalocyanines of the type [M(Pe)(L-L)| x .ISI
(Tollman and coworkers have reported similar shish kebab polymers of
the type |M(OEP))(L-L)| " (M = Fe, Ru, Os, and L-L = pyz, hpy, dabco) and
examined their conductivities.1X2 ls4 IH'' Many of the these shish kebab
coordination polymers can be doped w'ith iodine, which drastically
increases their conductivity (e.g., (7i()0K -
106
Chou et al.
Figure 97. Interporphyrin coordination in Zn[T(p-CN)PP]-2 C6H5N02 to form
a two-dimensional network. Guest molecules removed for clarity. Reprinted
with permission from Kumar, R. K.; Balasubramanian, S.; Goldberg, I.
Inorg. Chem. 1998, 37, 541. (c) 1998 American Chemical Society.
Figure 98. Crystal structure of Zn[T(p-CN)PP]-2 C6H5N02 showing
arrangement of guest molecules. Reprinted with permission from Kumar, R.
K.; Balasubramanian, S.; Goldberg, I. Inorg. Chem. 1998, 37, 541. (c) 1998
American Chemical Society.
41 / Porphyrin Materials Chemistry
107
Figure 99. Schematic illustration of three-dimensional porphyrin network
in Pd(TPyP),Cd(N03)2'8.6H20 in which porphyrins are represented as
squares and cadmium ions as circles. Solvent molecules are omitted for
clarity. Reprinted with permission from Abrahams, B. F.; Hoskins, B. F.;
Robsin, R. /. Amer. Chem. Soc. 1991, 113, 3606. (c) 1991 American Chemical
Society.
10~6Q~ 'em- 1 for [Fe'^PcXpyz)]^; ( = 2 x 10" 1 Q_1cm_l for
[Fen(Pc)(pyz)I254]^). The conductivity of these doped shish kebab
polymers depends on the interaction of the metal dn orbitals with the n*
level of the bridging ligand. Collman et al. found that the metal-metal
commu-
nication is greater for the better 7i-bonding metals (e.g., Os
> Ru > Fe) and the more 7i-acidic bridging ligand (e.g., pyz
> bpy dabco). The X-ray single crystal structure of the related
nonmacrocyclic metal complex [Co"-(dmgH)2-(Pyz)Joc confirmed that the
polymeric shish kebab-type structure can be formed with symmetric
multiatom bridges.186
b. Covalent, Conjugated Porphyrin Polymers
Porphyrins linked with conjugated organic bridges form another
subclass of conductive porphyrin materials. Work toward such polymers was
done by Crossley and coworkers, who synthesized linearly conjugated
porphyrin systems.179 Figure 116 illustrates their conjugated
tetrakis(porphyrin) materials. Preliminary spectroscopic data on this
system indicated a significant decrease in the HOMO-LUMO gap (by about
0.8 eV) compared with the porphyrin monomer. In related studies, Yu et
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