Synthesis of Phthalocyanines

Although these methods were applied for the synthesis of a number of various phthalocyanines with different central atoms (e.g., H2, Cu, Zn, Ni, Pt, Pd, Lu, etc.) not all metal phthalocyanines can be prepared by one of these methods. For example, the synthesis of silicon phthalocyanine, rhenium phthalocyanine and boron subphthalocyanine need more drastic conditions. In the following, an overview of the synthesis of phthalocyanines containing all central metals which have hitherto been inserted into the ring is given. 

Other examples of the synthesis of phthalocyanines by conversion of substituents of the macrocycle by hydrolysis are given below,... 

Table 1. Synthesis of Phthalocyanines by Ether Formation at the Central Metal...

Although direct reaction of lanthanide mono-porphyrins with free phthalo-cyanine or its lithium derivatives is generally more efficient than the template synthesis, and gives rise to mixed-ligand complexes, the template strategy can also be applied for synthesis of phthalocyanine-porphyrin complexes, as in the case of unsymmetric bisphthalocyanine complexes (Scheme 8.2, B(b)) [106, 136, 145, 146]. Thus, metallation of free porphyrins with lanthanide salts in TCB or n-octanol leads to single-decker complexes, which then react with phthalonitriles under the action of DBU in alcoholic media to give the desired compounds. 

In contrast to the azo dyes the synthesis of phthalocyanine blue is easy. It is made in one step from readily available compounds phthalic anhydride, urea, and a copper salt. 

The template synthesis of phthalocyanine complexes [ZnL] by the condensation of dicyano compounds with urea in the presence of zinc chloride and ammonium molybdate has been described.1136,1137... 

In this context it is interesting to note that benzonitrile, Ph—C=N, trimerizes to a triazine on a Raney nickel surface. It was assumed that Jt-bonded nitriles were involved in the reaction mechanism.10 This reaction resembles the well-known template synthesis of phthalocyanine complexes from phthalodinitrile. Formation of linear polymers [—C(R)—N—] occurs on heating aryl or alkyl cyanides with metal halides.11... 

Table 5.5 Influence of UV Irradiation on the Synthesis of Phthalocyanine Starting from 1,3-D in Different Solvents...

Scheme 4 Synthesis of phthalocyanine-polypyridyl ruthenium(II) dyad 46...

The use of metal ions as templates for macrocycle synthesis has an obvious relevance to the understanding of how biological molecules are formed in vivo. The early synthesis of phthalocyanins from phthalonitrile in the presence of metal salts (89) has been followed by the use of Cu(II) salts as templates in the synthesis of copper complexes of etioporphyrin-I (32), tetraethoxycarbonylporphyrin (26), etioporphyrin-II (78), and coproporphyrin-II (81). Metal ions have also been used as templates in the synthesis of corrins, e.g., nickel and cobalt ions in the synthesis of tetradehydrocorrin complexes (64) and nickel ions to hold the two halves of a corrin ring system while cycliza-tion was effected (51), and other biological molecules (67, 76, 77). 

Although the precise mechanism of formation of phthalocyanines is unknown, it is generally thought that isoindoline intermediates are involved. A notional cyclization process could be that shown in equation (43). Template synthesis of phthalocyanines can also be achieved starting with 1,3-diiminoisoindoline and various analogs can be obtained from combinations of starting materials. Ligands such as (96) and (97) can be synthesized in this manner. 

The macrocycle phthalocyanine contains 8 N atoms, but usually only the four N-atoms on the inner side of the cycle are able to coordinate. In fact, in most cases the synthesis of phthalocyanine is realized in the presence of a metal ion as the template. It is also possible to attach various substituents on the phthalocyanine macrocycle. As for porphyrin, when coordinating to a metal ion, the H-atoms of the two NH groups on the inner side of the phthalocyanine cycle are replaced. The incorporation of metal porphyrin and phthalocyanine complexes into porous crystals has been gaining increasing interest. The properties of the complexes located in zeolite channels or cages are usually different from those of the compounds in solution, and they may find applications in areas such as catalysis, photochemistry, electrochemistry, and biomimetics. 

Scheme 4.1 Synthesis of phthalocyanine-based sheet polymer 2.

Traditional and electrochemical methods for the synthesis of phthalocyanines and their metal complexes 00KK323. 

The synthesis of phthalocyanines [118] under the action of microwave irradiation can be performed easily in less time by using phthalonitrile as the substrate. Solvent-free conditions led to by far the best results and an important specific microwave effect was apparent (Eq. 86) ... 

Synthesis of phthalocyanine-2,9,16,23-tetracarboxylic acid cobalt(II) complex 48 (R = -COOH M = Co(II)) 0.26 g (2 mmol) water-free cobalt chloride, 1.54 g (8 mmol) 1,2,4-benzenetricarboxylic acid anhydride, 4.8 g (80 mmol) urea and around 20 mg ammonium molybdate are intensively mixed and heated under inert gas in a 100-mL glass vessel at 270 °C for 1 h. The blue-colored reaction mixture was pulverized, stirred in 400 mL 6 M aqueous HCl, filtered, intensively washed with 6 M HCl and then water and acetone. The product was treated in a Soxhlet apparatus with acetone and dried. The phthalocyanine tetracarboxylic acid amide obtained was saponified to the tetracarboxylic acid as follows. 1 g of the tetracarboxylic acid amide was heated in a mixture of 6 g KCl and 15 mL 2 M aqueous KOH at 90 °C until the ammonia evolution became weak. The filtered product was dissolved in a fairly small amount of 2 M NaOH and after filtration from byproducts separated with 2 M HCl and isolated by centrifugation. Purification was achieved by dissolving in 0.05 M NaOH, separation with 2 M HCl and centrifugation until the filtrate is free of chloride ions. Yield from 1 g tetracarboxylic acid amide 0.56 g (38%). IR (KBr) 1698, 1373, 1326, 1150, 1091, 743 cm . 

Synthesis of phthalocyanine-2,9,16,23-tetrasulfonic acid aluminum(III) complex 48 (R = -SO3 , M == Al(OH)) 10.73 g (40 mmol) 4-sulfophthalic acid monosodium salt, 1.28 g (24 mmol) ammonium chloride, 24.02 g (400 mmol) urea and 0.185 g (0.15 mmol) ammonium molybdate (all chemicals dried) were intensively mixed and placed in a 250 mL glass vessel under dry inert gas. 2 g (15 mmol) water-free aluminum trichloride (purity 99.99%) was added under inert gas. The mixture was heated at first at 140 °C and then within 30 min with stirring to 190 °C, followed by heating at 210 °C for 24 h under inert gas. The blue-colored reaction product was pulverized, treated for 24 h with 1 M aqueous... 

T. Kamei, T. Kato, E. Itoh, K Ohta, Discotic liquid crystals of transition metal complexes 47 synthesis of phthalocyanine-fullerene dyads showing spontaneous homeotropic alignment. J. Porphyrins Phthalocyanines 16, 1261-1275 (2012)... 

Synthesis of phthalocyanines with an extended system of TT-electron conjugation 13UK865. 

Lithium alkoxides play an important role in the oligomeric cyclization of dinitriles in the synthesis of phthalocyanines. The combination of potassium alkoxide-crown ether complex in a hydrocarbon solvent gives a very powerful catalyst for production of vinyl ethers from alcohols and acetylene (Eq. 7.9). ... 

Yanagisawa M, Korodi F, Bergquist J, Holmberg A, Hagfeldt A, Akermark B, Sun L (2004) Synthesis of phthalocyanines with two carboxylic acid groups and their utilization in solar cells based on nano-stmctured Ti02- J Porphyrins Phthalocyanines 8 1228-1235... 

Abstract This chapter describes the synthesis of phthalocyanines, subphthalocyanines and porphyrazines bearing fluorine atoms and/or perfluorinated alkyl or aryl groups. Influence of fluorination of macrocycle on its physico-chemical properties and perspectives of application is also briefly considered. 

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