Aromatic phthalocyanine

The second process to finish phthalocyanine, which is more important for P-copper phthalocyanine, involves grinding the dry or aqueous form in a ball mill or a kneader (64). Agents such as sodium chloride, which have to be removed by boiling with water after the grinding, are used. Solvents like aromatic hydrocarbons, xylene, nitrobenzene or chlorobenzene, alcohols, ketones, or esters can be used (1). In the absence of a solvent, the cmde P-phthalocyanine is converted to the a-form (57,65) and has to be treated with a solvent to regain the P-modification. The aggregate stmcture also has an impact on the dispersion behavior of a- and P-copper phthalocyanine pigments (66). 

Metal-free copper phthalocyanine blue, ie. Pigment Blue 16 [574-93-6] is one of the eadiest forms of phthalocyanine. Environmental concerns about copper in pigments tended to increase the use of metal-free copper phthalocyanine, but certain shortcomings (greenish hue, lack of stabiHty in aromatic solvents) allowed only specialty uses (109). The stabiH2ed a-NC-type is used in certain automotive coatings. 

More recently, activity in the held of the preparation of phthalocyanine-like compounds useful in material science concentrated on compounds containing only one triazole subunit (triazolophthalocyanines) 89 [94JCS(CC)1525 95ICA(230)153].These aromatic compounds (without or with metals in the cavity) present a problem of annular tautomerism of triazoles, but as yet it is known only that the NH is outside the cavity. 

Unsymmetrically monosubstituted phthalonitriles produce a mixture of four structural isomers of tetrasubstituted phthalocyanines.71,295 Other derivatives of phthalonitrile without a mirror plane perpendicular to the aromatic ring also lead to the formation of structural isomers. 

Although the substitution of a preformed phthalocyanine always leads to a complex mixture of more- or less-substituted products, the reaction is of major industrial importance. Besides the chloro- and bromocopper phthalocyanines, also polysulfonated phthalocyanines, which are used as water-soluble dyes, are produced by the reaction of copper phthalocyanine with the respective reactant. While typical aromatic reactions of the Friedel-Crafts type are also possible,333 direct nitration of the macrocycle commonly results in oxidation of the phthalocyanine. However, under mild conditions it is possible to introduce the nitro group directly into several phthalocyanines.334... 

In addition to nonheme iron complexes also heme systems are able to catalyze the oxidation of benzene. For example, porphyrin-like phthalocyanine structures were employed to benzene oxidation (see also alkane hydroxylation) [129], Mechanistic investigations of this t3 pe of reactions were carried out amongst others by Nam and coworkers resulting in similar conclusions like in the nonheme case [130], More recently, Sorokin reported a remarkable biological aromatic oxidation, which occurred via formation of benzene oxide and involves an NIH shift. Here, phenol is obtained with a TON of 11 at r.t. with 0.24 mol% of the catalyst. 

Anionic complexes can easily be prepared by the sulfonation of the aromatic rings in the complexes. Sulfonated cobalt phthalocyanine intercalated in a layered double hydroxide host was a stable catalyst for the oxidation of thiols162,163 and phenol derivatives.164 It was concluded that the complex has been intercalated with the plane of the phthalocyanine ring perpendicular to the sheet of the host (edge-on orientation) (Fig. 7.2). 

For systemic administration, the photosensitizer usually has to be delivered into the bloodstream by intravenous injection. Since the photosensitizer is a solid, this means that a solution or a stable suspension has to be provided. Metal complexes of the basic porphyrin and phthalocyanine nuclei are insoluble in water, so that some effort has to be made to render the system water soluble, or at least amphiphilic, by placing various substituents (e.g., S03H, C02H, OH, NR3+, polyether, aminoacid, sugar) on the periphery of the molecule. The aromatic character of the ligand offers a suitable opportunity for such substitutions to be made. Examples will appear frequently in the following sections. 

Phthalocyanine (Pc) molecules consisting of four interconnected isoindole units are synthetic analogues of porphyrins. They represent planar aromatic macrocycles with an 18 Jt-electron aromatic system, which is delocalized over an arrangement of alternated carbon and nitrogen atoms. For years, phthalocyanines have... 

A more recent example of induction of chirality in a discotic using chiral side chains is hexabenzocoronene 45.46 In the solid state this large aromatic system exhibits a strong Cotton effect, indicating that in a similar mechanism to that of the phthalocyanines, a helical arrangement of the molecules occurs. 

The use of electrochemical methods for the destruction of aromatic organo-chlorine wastes has been reviewed [157]. Rusling, Zhang and associates [166, 167] have examined a stable, conductive, bicontinuous surfactant/soil/water microemulsion as a medium for the catalytic reduction of different pollutants. In soils contaminated with Arochlor 1260, 94% dechlorination was achieved by [Zn(pc)] (H2pc=phthalocyanine) as a mediator with a current efficiency of 50% during a 12-h electrolysis. Conductive microemulsions have also been employed for the destruction of aliphatic halides and DDT in the presence of [Co(bpy)3]2+ (bpy=2,2 -bipyridine) [168] or metal phthalocyanine tetrasulfonates [169]. 

Y. Qiu, Y. Gao, P. Wei, and L. Wang, Organic light-emitting diodes with improved hole-electron balance by using copper phthalocyanine aromatic diamine multiple quantum wells, Appl. Phys. Lett., 80 2628-2630 (2002). 

The phthalocyanine [1-4] system is structurally derived from the aza-[18]-annulene series, a macrocyclic hetero system comprising 18 conjugated n-electrons. Two well known derivatives of this parent structure, which is commonly referred to as porphine, are the iron(III)complex of hemoglobin and the magnesium complex of chlorophyll. Both satisfy the Htickel and Sondheimer (4n + 2)- electron rule and thus form planar aromatic systems. 

Copper Phthalocyanine Blue is the copper(II) complex of tetraazatetrabenzo-porphine. As shown below, the mesomeric structures indicate that all of the pyrrole rings simultaneously contribute to the aromatic system ... 

The -modification as a rule evolves as a more coarse-grained material than the a-phase. It is prepared by milling the crude Copper Phthalocyanine Blue with salt in the presence of a crystallization stimulating solvent. Aromatic hydrocarbons, esters, or ketones are normally used. 

Flocculation may likewise be prevented through partial introduction of dialkyl-aminomethylene groups into the aromatic ring system of the copper phthalocyanine molecule. The copper phthalocyanine structure tightly attaches the basic groups... 

Copper phthalocyanine pigments also demonstrate good overall stability to organic solvents. A number of solvents, however, especially aromatics, may cause a change of modification in unstable types or overcrystallization in stable varieties. This phenomenon is largely due to the tendency of the stable phase to nucleate. The particle size of the resulting cystals decreases as the number of nuclei rises. (3-Copper Phthalocyanine Blue is the thermodynamically stable modification. 

Under the designation P.B.15 4, the Colour Index lists (3-Copper Phthalocyanine Blue types which are stabilized towards flocculation. These products show largely the same coloristic and fastness properties as P.B.15 3 types, but often exhibit much better rheology. As with stabilized a-Copper Phthalocyanine Blue types, stabilization through surface treatment has proven to decrease the solvent fastness of 3-Copper Phthalocyanine Blue, sometimes considerably so, making the pigment more sensitive to aromatics, alcohols, ethylene glycol, and ketones. 

Phthalocyanines 244 and hemiporphyrins 245 and 246 are aromatic systems. Extended conjugation confers special properties to these molecules that make them building blocks for new molecular organic materials with useful electric and nonlinear optical applications (Scheme 85).288... 

Pyrenes appear to be once again amongst the most useful linkers, and the attachment of metal-complexed porphyrins has already been discussed in the section on small aromatic molecules. Porphyrin rings bearing a metal center can also be directly adsorbed on the CNTs sidewalls, and they have been shown to exhibit an increased charge transfer from the metal to the tubes, presumably mediated by the aromatic moieties [100]. A similar behavior is exhibited by the phthalocyanine-based complexes [101]. Other aromatic molecules can be used for appendages, including triphenylphos-... 

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