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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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Substitution of the larger tetra(trimethylamino)-4-phenyl)porphyrin
Zn(II) derivative, inhibited evolution of hydrogen gas from a similar
system. Examining the electrochemistry of adsorbed Zn(TMPyP)Cl and
Zn(TMPyP)Cl on zeolite Y, a positive shift of the reduction potential by
200 mV was reported versus aqueous solution.151
Other zeolitic materials with adsorbed porphyrins on external surface
include the immobilization of Sn(TMPy P)C12 and Sn(TPy P)C12 on zeolite Y
for use as a solid photosensitizer material in the photodegradation of
organic substrates.152 Zeolite supported Fe[T("-MPy)P] (n =2, 3 or 4) was
explored in heterogeneous catalytic autoxidations of sulfite.
It was observed that the ortho-methyl pyridyl-substituted porphyrinic
materials demonstrated approximately twice the catalytic activity of the
meta- and para-substituted systems.153 A Cu(TPP) / zeolite Y material was
coated onto an electrode as part of a carbon paste to be used as an
electrochemical sensor. No catalytic activity was noted when glutathione
was used as a substrate for electroxidation, and cysteine was observed to
block electroxidation, but efficient activity for the electrocatalytic
oxidation of hydrazine was observed. The authors cited this as an example
of conferred selectivity due to the presence of the Cu(TPP) / zeolite
material (Figure 107).154
The first of the so-called "ship-in-bottle" porphyrin systems, in
which the porphyrin macrocycle is synthesized from molecular precursors
inside the zeolite cavities, was
41 / Porphyrin
Materials Chemistry
91
Figure 72. Packing arrangement observed in Zn(T(p-OH)PP)'3C7H8 and xylene
species (average guest position represented by hexamethylbenzene).
Reprinted with permission from Goldberg, I.; Krupitsky, H.; Stein, Z.;
Hsiou, Y.; Strouse, . E. Supramol. Chem. 1995, 4, 203. (c) 1995 Gordon and
Breach Publishers.
reported by Tatsumi and coworkers.155 Refluxing pyrrole and acetaldehyde
under Rothmund conditions in the presence of ion-exchanged zeolite Y led
to the formation of metalated 5,10,15,20-tetramethylporphyrin, H2(TMP)
within the zeolitic pore structure. H2(TMP) is cited as being sterically
amenable to the internal zeolite pores. Diffuse reflectance UV-Vis
spectroscopy was used to characterize the materials (Figure 108).
Significantly increased yields of cyclohexanol and cyclohexanone from the
oxidative conversion of cyclohexane were reported for the ion-exchanged
xeolite complexes of Mn(II) and
Fe(II) complexes of TMP versus the free metalloporphyrins.
The dioxygen affinity of Co(TMP) encapsulated in zeolite Y by similar
"ship-in-bottle" methodology was studied by Govind et al.l5b The
porphyrin-free zeolite exhibits quantitatively similar absorption
isotherms for both oxygen and argon. In comparison, the Co(TMP) encapsu-
Iated-zeolite compound was observed to absorb eight times the amount of
oxygen to argon (Figure 109).
A larger-pore zeolite, MCM-41, was used for the first reported
encapsulation of a tetraphenylporphyrin and the
92
Chou et al.
2--
Figure 73. Crystal packing in Zn[T(p-OH)PP]-2C7H802H20. Reprinted with
permission from Goldberg, I.; Krupitsky, H.; Stein, Z.; Hsiou, Y.;
Strouse, . E. Supramol. Chem. 1995, 4, 203. (c) 1995 Gordon and Breach
Publisher.
Figure 74. Layered structure in Zn[T(p-OCH i)PP]-CfiH,;OH;0 (top):
illustration of channels in the same material (bottom). Reprinted with
permission from Goldberg, I.; Krupitsky, H.; Stein. Z.; Hsiou, Y.;
Strouse, . E. Supramol. Chem. 1995, 4, 203 c'- 1995 Gordon and Breach
Publishers.
first porphyrin-ligated second-row transition metal. Surface modification
of the zeolite with 3-aminopropyltiiethoxysi-lane (APTES) was necessary
to achieve encapsulation of ruthenium (11) 5.10.15.20-teira(4-
chlorophenyl)poiphyrin, Ru|T(p-Cl)PP)(CO)(EtOH). The encapsulated
porphyrin/ zeolite material was characterized by vibrational and diffuse
reflectance spectroscopy and powder X-ray diffraction (Figure I 10).
Twenty-to-forty-times-highcr product turnovers were reported for
oxidative catalysis of alkcne substrates by /m-butylhydroperoxide with
the potphvrin/MCM-41 material versus free Ru[T(p-Cl)PP](CO)(ElOH).n'
Kevan and coworkers produced, via physisorption, H?(TPP) encapsulated
within mesoporous MCM-41 hosts. Generated by photoinduced electron
transfer, the long-lived I-- ) cation was characterized by electron
spin resonance (ESR) and dilTusc-reflectance electronic spectroscopy
(Figure 111). For a series of H:(TPP)/C,,-MCM-41. Cn = C|0. 11, |_| and
C-, materials, an increase in photo-vield was observed to correspond
with an increase in alkyl chain length (causing increased pore size). The
photoioni-zation efficiency was observed to increase along the series
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