Zinc phthalocyanine preparation

Zinc phthalocyanine (PcZn) is prepared from phthalonitrile in solvents with a boiling point higher than 200 C, e.g. quinoline277,278 or 1-bromonaphthalene,137 or without solvent in a melt of phthalonitrile.83,116 The zinc compound normally used is zinc(ll) acetate or zinc powder. The reaction of zinc(II) acetate with phthalic acid anhydride, urea and ammonium mo-lybdate(VI) is also successful.262 The metal insertion into a metal-free phthalocyanine is carried out in an alcohol (e.g.. butan-l-ol).127,141,290 This reaction can be catalyzed by an alkali metal alkoxide.112,129... 

The tetrasubstituted phthalocyanines are formed as a mixture of four structural isomers (see p 736). The description of this substitution pattern is 1,8,15,22-, neglecting the existence of different isomers. Abbreviations, like 1,4-tetrasubstituted phthalocyanine, are often used. An example of the preparation of a tetrasubstituted phthalocyanine without solvent is the formation of zinc phthalocyanine 4. 

The preparation of a novel pentadentate ligand, 2-hydroxy-5-methylisophthalalde-hyde bis(p-methoxy thiobenzoylhydra-zone), was described together with the chloro-bridged Zn(II) complexes [127]. Synthesis and electrochemical properties of some long-chain 1,4,8,11,15,18,22,25-ocla-alkylaled metal-free and zinc phthalocyanines were presented by Swarts etal. [128]. Ihe zinc derivatives show higher liquid crystalline behavior than the free-metal compounds. 

Figure 29 MALDI-TOF mass spectrum of zinc phthalocyanine 42 showing the formation of coordinating pol3miers (a). TEiM images of samples of 42 prepared from a CHCI3 solution (b). (Reproduced from Ref. 57b. American Chemical Society, 2007.)...

The exchange of lithium in a dililhium phthalocyanine is a useful tool to prepare metal (e.g., zinc) or metal-free phthalocyanines. For this purpose, the dilithium phthalocyanine is prepared by reaction of phthalonitrile and lithium alkoxide in an alcohol, e.g. pentan-l-ol. In most cases, the lithium phthalocyanine is not separated but directly converted into the respective phthalocyanine by treatment with metal salts or, in the case of metal-free phthalocyanine, with acid or water. 

Similarly, zinc(II) l,8,15,22-tetra(4-butylbenzyloxy)phthalocyanine can be prepared.298 In this case only the C4ll isomer is produced in 80% yield.298... 

In the same manner, zinc(II) phthalocyanine 12 can be prepared by metal/metal exchange from a 2,3,9,10,16,17,23,24-octasubstituted alkali-metal phthalocyanine. 

Octaalkylphthalocyanines with the alkyl groups at the 1,4,8,11,15,18,22,25- positions have been synthesized as their zinc(II) complexes for PDT studies.238 Tumor localizing and tumor photosensitizing properties have been presented for the octapentyl239 and octadecyl240 compounds. Zinc(II) tetrakis(w-hydroxyalkyl)phthalocyanines have been prepared and tested in vivo, the tetrakis(3-hydroxypropyl) compound being the most active.241... 

Initial compounds tetracyanodibenzo(l,4,7,10-tetiathia-(12-crown-4)) 1, 4-nitro-1,2-dicyano benzene and 4,5-bis(hexylthio)phthalonitrile were available from earlier study. Nitro-substituted dimeric Co(II) phthalocyanine 3 was prepared by reaction of tetracyanodibenzol-(l,4,7,10-tetiathia-(12-crown-4)) 1, 4-nitro-l,2-dicyanobenzene 2 and zinc(ll) acetate in amyl alcohol. 

Although strictly not a dendritic system, Agar et al.[75] have reported the preparation of copper(n) phthalocyaninate substituted with eight 12-membered tetraaza macrocycles as well as its nickel(n), copper(n), cobalt(n), and zinc(n) complexes. Thus, the use of the l,4,7-tritosyl-l,4,7,10-tetraazacyclododecane offers a novel approach to the 1 — 3 branching pattern and a locus for metal ion encapsulation. 

Nucleobases and nucleosides are common motifs for hydrogen-bonded supramolecular arrays. Ng et al. first reported a series of phthalocyanine-nucleobase conjugates [64], The tetra-adenine phthalocyanine 64 was prepared by standard <9-alkylation of zinc(II) tetrahydroxyphthalocyanine with 9-(2-bromoethyl)adenine in the presence of K2CO3. The fluorescence of 64 is quenched substantially upon addition of thymine-substituted 9,10-anthraquinone 65, and the rate is much faster compared with that for the situation when the unsubstituted 9,10-anthraquinone is used as the quencher. These results suggest that 64 forms a supramolecular complex with 65 through the Watson-Crick base-pairing interactions. 

In order to increase the solubility of porphyrin and phthalocyanine complexes, several structural modifications have been made, a, jS, y, 6-Tetra-(4-pyridyl)-porphin complexes of copper(II), nickel(II), and zinc(II) have been synthesized (35) and their ultraviolet spectra determined in chloroform and in acid solution. By utilizing sulfonic acid groups to increase solubility, complexes of 4,4, 4",4" -tetrasulfophthalocyanine complexes of many metals were prepared (94j 95). This chelating agent was found to have a ligand field strength comparable to cyanide (94y 95). 

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