Phthalocyanine crystal modifications

The cmde copper phthalocyanine must be treated to obtain a satisfactory pigment in regard to the crystal modification and optimal particle size... 

Some references cover direct preparation of the different crystal modifications of phthalocyanines in pigment form from both the nitrile—urea and phthahc anhydride—urea process (79—85). Metal-free phthalocyanine can be manufactured by reaction of o-phthalodinitrile with sodium amylate and alcoholysis of the resulting disodium phthalocyanine (1). The phthahc anhydride—urea process can also be used (86,87). Other sodium compounds or an electrochemical process have been described (88). Production of the different crystal modifications has also been discussed (88—93). 

Copper Phthalocyanine Blue exhibits more than one crystal modification. This is also true for the metal-free ligand whose greenish blue crystal phase was used on a large industrial scale for a certain period of time (Sec. 3.1.2.6). Free-base Phthalocyanine Blue was largely displaced by (3-Copper Phthalocyanine Blue as it became possible to produce the latter more economically (Sec. 3.1.2.3). 

Knowledge of the most important types of copper phthalocyanine pigments is useful for the understanding of the processes concepts underlying pigment manufacture. Heading the list are the a- and [i-modil i cations of unsubstituted Copper Phthalocyanine Blue (Sec. 3.1.2.3). The a-modification exhibits an unstabilized and a stabilized form as to change of crystal modification. 

Unsubstituted Copper Phthalocyanine Blue is polymorphous. X-ray diffraction diagrams point to five different crystal modifications (a, (3, y, 8, e) (Fig. 91). The relative thermodynamic stability of the individual cystal phases decreases in the following order (3>e>8>a = y [13-16],... 

The synthesis of the crystal modification is controlled primarily by the finishing technique of the crude pigment. There are basically two different methods to produce a finely dispersed pigment treatment with acid to form copper phthalocyanine salts, followed by precipitation in water on the one hand, and mechanical treatment (milling, kneading) on the other hand. The following methods are used ... 

The similarly blue and equally polymorphous metal-free phthalocyanine existing in five different crystal modifications (a, (3, y, k, t) is chemically somewhat less stable than its copper complex [26] it decomposes slowly in a sulfuric acid solution. On the other hand, it can be chlorinated to afford metal-free Phthalocyanine Green. 

The five crystal modifications of copper phthalocyanine blue pigments which have been discovered thus far differ in terms of coloristics. The (3-modification provides the most greenish and cleanest shades of blue, the a-form is distinctly redder than the (3-modification, and the e-phase is even redder than the a-form. y- and S-Copper Phthalocyanine Blue have not yet been commercialized. 

The a- and (i-types of Copper Phthalocyanine Blue reign supreme among commercially available phthalocyanine pigments. There is also an increasing amount of interest in the phase-stabilized form of the a-crystal modification. Both modifications are also supplied as flocculation resistant types. 

P.Gr.7 type pigments provide a bluish green shade. The fact that P.Gr.7 only exists in one crystal modification which resembles that of a-Copper Phthalocyanine Blue eliminates the problems which are associated with the possibility of phase transition. 

Defintion Bright blue copper phthalocyanine pigment avail, in the a or p crystal modification Empirical CjjHieCuN,... 

The ability to nucleate p crystals can be explained by the surface geometry of phthalocyanine crystals. For a modification of the phthalocyanine the distance between grooves on the lateral surfaces equals 1.19 nm (Honigmann et al. 1%5). This dimension is comparable with the spacing of 1.1 nm between helices of the same hand in the trigonal cell of the P form of polypropylene. 

Definition Bright blue copper phthalocyanine pigment avail, in the a or p crystal modification Empirical C32H16CUN8 Formula (C6H4C2N)4N4Cu Properties Bright blue microcryst. with purple luster insol. in water, alcohol m.w. 576.08 Toxicology LD (oral, rat) >15 g/kg, (IP, rat) > 3 g/kg TSCA listed... 

The reaction of urea, CuCl and phthalic anhydride is carried out at ca.200 °C in a process lasting 2 to 3 hours, using ammonium molybdate as a catalyst nitrobenzene, trichlorobenzene or kerosene can be used as solvents. When phthalodinitrile is used, the reaction is carried out without catalyst at ca. 200 °C as a baking process or in solution. When the crude phthalocyanine has been produced, it is conditioned to suitable crystal modifications, e.g. by dissolving in sulfuric acid and subsequent hydrolysis, or treatment with organic solvents. 

Photoelectrical properties of phthalocyanine powders and their films on a variety of substrates have been the object of numerous investigations. Photoconductivity is affected by the nature of the phthalocyanine substrate as well as its crystal modification, doping agents employed [201], and by the way the... 

As in many other pigment classes such as copper phthalocyanines and quinacri-dones, different crystal modifications of DPP pigments have been identified. ... 

Phthalocyanine blue is known to exist in several crystal modifications, with its three more important crystal forms, alpha, beta and epsilon, all industrially available. The beta form is greenish blue, and the important epsilon form is the most reddish shade of blue. Its halogenated derivatives are also used as important green pigments. 

Although titanyl phthalocyanine is known to have two crystal forms (alpha and beta), in the course of OPC investigations over the past fifteen years, many new crystal modifications were discovered, exhibiting different patterns of X-ray diffraction spectra. 

The shape of the titanyl phthalocyanine molecule is not planar but pyramidal, where the titanium atom is out of the plane of the phthalocyanine macrocycle and the symmetry of the molecule is reduced from D4h to C4h. Accordingly, titanyl phthalocyanines can have more crystal modifications than such planar molecules as copper phthalocyanine or metal-free phthalocyanine. General procedures used in the development of new crystal modifications involve solvent treatment of amorphous titanyl phthalocyanines obtained by acid pasting or milling procedures. 

Like many of the high-performance pigments such as quinacridones, DPPs and phthalocyanine pigments, THI pigments can exist in more than one crystal form. So far, three different crystal modifications with different crystal packings have been identified. 

Very unstable modifications, like the reddish, chlorine-free a-copper phthalocyanine, can be stabilized with amides or salts of copper phthalocyanine sulfonic acids (59—63). Mixture with other metal phthalocyanines, eg, tin, vanadium, aluminum, or magnesium, also inhibits crystallization change and poor performance in binders and prints (flocculation) due to the hydrophobic character of unsubstituted phthalocyanines. 

Abstract In this chapter, recent progress in the synthesis, crystal structures and physical properties of monomeric phthalocyanines (Pcs) is summarized and analysed. The strategies for synthesis and modification of Pcs include axial coordination of central metal ions, peripheral substitution of Pc rings and the ionization of Pcs. The crystal structures of various typical Pcs, especially the effects of different synthetic and modification strategies on the supramolecular assemblies of Pcs via %—% interactions between Pc rings, are discussed in detail. Finally, the UV-vis spectroscopic, conducting, magnetic and catalytic properties of some Pcs with crystal structures are presented briefly, and the correlations between various properties and the molecular structure discussed. 

Keywords Crystal structure Modification Phthalocyanine Property Synthesis... 

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. 

---