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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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mixed-aldehyde condensation reactions. These arrays are soluble in common
organic solvents and can be easily metalated by treating the
corresponding arrays with Zn(02CCH3)2 in methanol. Two important results
with regard to the photophysical properties of the BDPY-porphyrin arrays
are: (1) the intense
blue-green absorption bands of the BDPY dyes complement the porphyrin
Soret bands; and (2) the energy-transfer efficiency between the BDPY dyes
and the central porphyrin is nearly quantitative in the arrays with one
or two BDPY units, but drops (to 80-90%) in the arrays with eight BDPY
units. The authors suggest that "the BDPY-porphyrin arrays are excellent
candidates for inclusion in light-harvesting model system and as input
elements of prototypical molecular photoic devices."
Another popular approach to the construction of suprarmolecular
porphyrin arrays uses metal-ligand interactions. 113-12(1 Most of this
work has concentrated on
5,10,15,20-pyridylporphyrin (TpyP) and the porphyrin arrays prepared from
TpyP range from the dimeric molecule to polymeric networks. This
synthetic strategy was adopted by Lehn and Drain for the preparation of
multiporphyrin arrays with square architecture (Figure 55).113 Their most
impressive assembly is a 21-component structure consisting of nine
porphyrins linked together by 12 palladium cations (Figure 56).121 It is
composed of three different kinds of porphyrins: a tetrapyridylporphyrin
coordinated to four metal ions forms the center of the array;
tripyridylporphyrins coordinated to three metal ions constitute the sides
of the array; and the dipyridyl porphyrins form the corners. The
synthesis involved placing these components in solution with the correct
ratio at room temperature. The product was isolated in an amazing yield
of 90%.
In an effort to prepare new biomimetic light-harvesting systems,
Therien and coworkers adopted recently developed metal-mediated cross-
coupling methodologies and synthesized a new class of poiphyrin arrays.
I_~ The porphyrins are linked together by yne and polyynyl units (Figure
57). They believe that ethyne, oligoethyne and multiethyne linkages
between the porphyrins will produce multichromophoric systems with
unusually strong excitonic and electronic coupling. The most important
feature of these porphyrin arrays is that their spectroscopic data bear
strong similarity to that of the purple bacterial light-harvesting
complexes as well as to the light-harvesting structures in green
photosynthetic bacteria.
III. Porphyrinic Solids
A. MICROPOROUS SOLIDS
A number of researchers have explored synthetic strategies for the
construction of porphyrinic solids that contain molecule-sized cavities
or channels. Porphyrin macrocycles can be envisioned as flat, rigid,
geometrically square building blocks approximately 1 nm wide. Out-of-
plane twisting by the 5,10,15,20-substituted phenyl rings (as
necessitated by steric constraints) provides a route to construct
structures extending beyond the porphyrin macrocycle plane. Chemical
modification of the perimeter is facile in many cases. Additionally the
thermal stability makes them an attractive precursor for potential use at
elevated temperatures. Furthermore, metalloporphyrins have demonstrated
catalytic ability in a wide variety of reactions;123'124
41 / Porphyrin Materials Chemistry
73
(-\)
Figure 50. 1,4-Phenylene-bridged linear porphyrin arrays. (A) dimer. (B)
trimer to nonamer. Reprinted with permission from Osuka, A . Shimidzu, H.
Anqew. Chem. Int. Ed. Engl. 1997, 16. 135- " 1 997 |ohn Wiley & Sons,
Inc.
Figure 51. 5,10,15,20-linked porphyrin arrays. Reprinted with permission
from Osuka, A.; Shimidzu, H. Angew. Chem. Int. Ed. Engl. 1997, 36, 1 35.
(5) 1 997 |ohn Wiley & Sons, Inc.
thus, porous metalloporphyi'in networks have the potential to act as
shape- and size-selective catalysts.
1. Porous Molecular Porphyrin Stuctures
Strouse and coworkers1 ^ examined the extensive crystal structure library
of free-base and metalated porphyrin lattice elathrates in which the
predominant inter-molecular bonding interactions were of a very weak
nature. In addition to Fb(TPP), their database included simple
substituted porphyrins such as u-ainino- HU[T(o-NH >)PP|, /;-methoxy-
H:[T(p-OCH,)PP| and/>-bromo-H.[T(p-Br)PP| tetraphenylporphyrins. While
the most commonly studied metalloporphyi'in was the Zn(ll) species, at
least eleven other metalloporphyrins were examined. They realized that
the large majority of these structures contained a high concentration of
solvates and were in effect '"porphyrin sponges."

These TPP-derivative materials were held together by van der Waals forces
and found to exhibit comparable
packing modes generalized as the simple hody-eentered-cubie (BCC)
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