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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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mesophasic behavior (~ 20 癈) than those with two lateral chains (Figure
17). Nematic mesophases, more disordered than the smectic type, were
observed for these materials. This is also attributed to the presence of
the lateral chains.27
Further attempts to restrict porphyrin-to-porphyrin interactions
culminated in the synthesis of novel "donor-acceptor" and "strapped"
porphyrin compounds. Instead of alkoxyl chains, lateral p-
nitrophenylsulfonyl groups were substituted on the 5,10,15,20-phenyl ring
(Figure 18). The phenyl ester species (R = 󙾼-0-镅7蛗5) displayed a
high melting point and a small nematic mesomorphic range (28 癈) before
decomposing. The cyclohexane ester (R = CftHiQ-nCyHij) decomposed
directly from the melt. Significant distortion of the macrocyclic ring in
the xylene
Figure 16. Structure of ester-substituted di-phenyl porphyrin with single
lateral chain.
Figure 18. Structure of o-(p-nitrophenylsulfonyl)oxy-substituted Zn" di-
phenyl porphyrin (R = C6H4-0-nC7HiS or R = C6H10-nC7H15). Reprinted with
permission from Wang, Q. .; Bruce, D. W. /. Chem. Soc., Chem. Commun.
1996, 2505.
Figure 17. Structure of ester-substituted di-phenyl porphyrins with two
lateral chains (R = C6Hio-n-C7Hls; or R = C6H4-0-n-CmH2m + b m = 7,8.).

Figure 19. Structure of "strapped" Zn" di-phenyl porphyrin
(R = C6H4-0-nC7H15). Reprinted with permission from Wang, Q. .;
Bruce, D. W. Tetrahedron Lett. 1996, 37, 7641.
41 / Porphyrin Materials Chemistry
"strapped" porphyrin complex (R = C6H4-0-nC7H|5), was cited for the lack
of mesogenic behavior (Figure 19).28
Efforts have been directed to increasing the "rod-like" geometry of
the zinc porphyrin systems by extending the linear expanse through
additional phenyl ester groups (Figures 20 and 21). This approach
generally resulted in lower temperatures for the onset of the first phase
transition, however, in the some cases, this was a crystalline-to-
crystalline phase change. At high temperatures, both a smectic and a
nematic phase were observed in the 3,4-n-dodecyloxyphenyl compound. One
system that featured eight linear phenyl ester moieties but no lateral
chains dangling over the porphyrin macrocyclic ring (Figure 20, Y =
OC12H25; n= 12, m = 2) manifested a columnar mesophase. A relatively low
phase transition (50 癈) to a nematic phase was seen in the material with
both lateral chains and eight linear phenyl ester groups (Figure 21, Y =
OC|2H2S; m - 2). The material cleared to an isotropic fluid at 153 癈.29
Ohta and coworkers studied the liquid-crystalline behavior of a series
of disubstituted phenyl porphyrins. Similar to the highly substituted
tetraphenyl species, 5,15-bis[3,4,3",4"-tetra(alkoxy-o-
terphenyl)]porphyrins, H2[B-(CnH2nflO)mTPj where n = 12 or 16 and m =4 or
8, were prepared with as many as eight long alkoxyl chains (Figure 22). A
discotic, rectangular disordered columnar (Drd), arrangement was observed
for H2[B(C|2H2sO)8TP]. Increasing the alkyl chain length (e.g.,
2[(褆6顽30)8倚)] produced a material that also exhibited a Drd columnar
mesophase, which cleared to an isotropic liquid at nearly the same
temperature as the dodecyloxy compound. Substitu-
Figure 20. Structure of catenane-substituted di-phenyl porphyrin systems
(Y = H; n = 10, m = 0; or Y = H; n - 12, m = 1;
Y = OC12H25; n = 12, m = 2). Reprinted with permission from Wang, Q. .;
Bruce, D. W. Angew. Chem. Int. Ed. Engl. 1997, 36, 150.
Figure 21. Structure of catenane-substituted di-phenyl porphyrin systems
with lateral chains (Y = H; m = 1; or Y = OC^H^; m =2). Reprinted with
permission from Wang, Q. .; Bruce, D. W. Angew. Chem. Int. Ed. Engl.
1997, 36, 150.
Figure 22. Structure of 5,15-bis(3,4,3",4"-tetradodecyloxy-o-ter-
phenyl)porphyrin derivatives (R1 = R2 = C12H250; or R1 =
R2 = C16H 330; or R1 =C12H250, R2= H).
Figure 23. Structure of 5,15-bis(3,4-didodecyloxyphenyl) porphyrin.
Figure 24. Structure of 5,15-bis(4-didodecyloxybiphenyl) porphyrin.
tion of one of the dodecyloxyl chains on each porphyrin with a proton
generated a material with two discotic lamellar mesophases. The clearing
point of this compound (228.6 癈) was approximately 100 higher than that
of either di-substituted compounds (136.7 and 132.9 癈, respectively).18
Two other di-substituted species were examined by Ohta and coworkers.
The tetra alkoxyl-containing 5,15-bis(3,4-didodecyloxyphenyl)porphyrin
displayed a discotic lamellar mesophase with a melting point of 60.4 癈
and clearing point of 200.7 癈 (Figure 23). Four crystalline phases and
one undetermined mesophase were delineated for 5,15-bis(4-
didodecyloxybiphenyl)porphyrin between initial crystalline phase
transitions at 40.1 癈 to melting to the mesomorphic material at 430.9 癈
(Figure 24). The material was observed to decompose at 450.5 癈.18
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