Phthalocyanines reactions

Fig. 6. The chemistry of silicon phthalocyanines. Reaction pathway (1) Py/NH4OH ...

Fig. 7. The chemistry of germanium phthalocyanines. Reaction pathway (1), (2) Quinoline at reflux (3) Py/NHUOH (4) CeEUOH/CuHe (5) heat (6) Ph2Si(OH)2/CeHe (7) CeH6CH2OH (8) 385°C.

Fig. 9. The chemistry of chromium phthalocyanines. Reaction pathway (1) sublime (2) CH3COOH (3) H20 (4) O2/H2O (5) alcohol (6) HCl/MeOH (7) H20/EtOH/ CH3COOH (8) alkali (9) acid (10) acid anhydride (11) KCN/EtOH (12) reflux acetic anhydride.

Fig. 10. The chemistry of manganese phthalocyanines. Reaction pathway (1) NaCN/EtOH/N2 (2) alcohol (3) EtOH/NaOH (4) Py/02 (5) CHsCOOH (6) heat (7) Py (8) CH,COOH (9) MeOH/KCN, KCNS, KCNSe (10) EtOH/NaOH.

In order to make these oxidative reactions of 1,3-dienes catalytic, several reoxidants are used. In general, a stoichiometric amount of benzoquinone is used. Furthermore, Fe-phthalocyanine complex or Co-salen complex is used to reoxidize hydroquinone to benzoquinone. Also, it was found that the reaction is faster and stereoselectivity is higher when (phenylsulflnyl)benzoquinone (383) is used owing to coordination of the sulfinyl group to Pd, Thus the reaction can be carried out using catalytic amounts of PdfOAcji and (arylsulfinyl)benzoquinone in the presence of the Fe or Co complex under an oxygen atmosphere[320]. Oxidative dicyanation of butadiene takes place to give l,4-dicyano-2-butene(384) (40%) and l,2-dicyano-3-butene (385)[32l]. 

Oxidation can also occur at the central metal atom of the phthalocyanine system (2). Mn phthalocyanine, for example, can be produced ia these different oxidation states, depending on the solvent (2,31,32). The carbon atom of the ring system and the central metal atom can be reduced (33), some reversibly, eg, ia vattiag (34—41). Phthalocyanine compounds exhibit favorable catalytic properties which makes them interesting for appHcations ia dehydrogenation, oxidation, electrocatalysis, gas-phase reactions, and fuel cells (qv) (1,2,42—49). 

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). 

Phthalocyanine sulfonic acids, which can be used as direct cotton dyes (1), are obtained by heating the metal phthalocyanines in oleum. One to four sulfo groups can be introduced in the 4-position by varying concentration, temperature, and reaction time (103). Sulfonyl chlorides, which are important intermediates, can be prepared from chlorosulfonic acid and phthalocyanines (104). The positions of the sulfonyl chloride groups are the same as those of the sulfonic acids (103). Other derivatives, eg, chlormethylphthalocyanines (105—107), / /f-butyl (108—111), amino (112), ethers (109,110,113—116), thioethers (117,118), carboxyl acids (119—122), esters (123), cyanides (112,124—127), and nitrocompounds (126), can be synthesized. 

Testing of phthalocyanines includes crystallization (qv), flocculation, and appHcation in paints, plastics (qv), and printing inks (1). The ASTM standard specifications include CuPc in dry powder form for various appHcations (153). The specifications cover color (qv), character or tint, oil absorption, reactions in identification tests, and dispersions and storage stabiUty. Quantitative deterrninations are possible with ceric sulfate (30) or sodium vanadate (154). Identification methods are given (155), including tests for different appHcations. 

Phthalocyanines are excellent lubricants at temperatures of 149—343°C (191). Combinations with other lubricants, like grease, molybdenum, or tungsten sulfides, have found appHcations in the automotive industry or professional drilling equipment (192—195). Further uses include indicators for iron(Il), molybdenum(V), and uranium(IV) (196) or redox reactions (197), medical appHcations like hemoglobin replacements (198) or sterilisation indicators (199), or uses like in gas filters for the removal of nitrogen oxides from cigarette smoke (200). 

Chemical and biological sensors (qv) are important appHcations of LB films. In field-effect devices, the tunneling current is a function of the dielectric constant of the organic film (85—90). For example, NO2, an electron acceptor, has been detected by a phthalocyanine (or a porphyrin) LB film. The mechanism of the reaction is a partial oxidation that introduces charge carriers into the film, thus changing its band gap and as a result, its dc-conductivity. Field-effect devices are very sensitive, but not selective. 

Dioxazine Violet. Carba2ole Dioxa2ine Violet is prepared by the reaction of two moles of 2-ainino-A/-ethylcarba2ole with chloranil. This violet may be used in most plastics for shading phthalocyanine blues, because it has comparable light fastness. At relatively high temperatures, it may be subject to slow decomposition. 

Halide complexes are also well known but complexes with nitrogen-containing ligands are rare. An exception is the blue phthalocyanine complex formed by reaction of Be metal with phthalonitrile, 1,2-C6H4(CN)2, and this affords an unusual example of planar 4-coordinate Be (Fig. 5.5). The complex readily picks up two molecules of H2O to form an extremely stable dihydrate, perhaps by dislodging 2 adjacent Be-N bonds and forming 2 Be-O bonds at the preferred tetrahedral angle above and below the plane of the macrocycle. 

Green-yellow salts of the tetrahedral [MX4] (X = Cl, Br, I) ions can be obtained from ethanolic solutions and are well characterized. Furthermore, a whole series of adducts [MnX2L2] (X = Cl, Br, I) are known where L is an N-, P- or A -donor ligand, and both octahedral and tetrahedral stereochemistries are found. Of interest because of the possible role of manganese porphyrins in photosynthesis is [Mn (phthalocyanine)] which is square planar. The reaction of aqueous edta with MnC03 yields... 

Phthalocyanines have been synthesized with nearly all metals of the periodic table.77 Normally they are formed in a single-step reaction from available derivatives of phthalic acid, in particular phthalic acid (see Section 2.1.1.1.), phthalic anhydride (see Section 2.1.1.2.), phthalimide (see Section 2.1.1.3.), 2-cyanobenzamide (see Section 2.1.1.4.), phthalonitrile (see Section 2.1.1.5.), isoindolinediimine (see Section 2.1.1.6.), or 1,2-dibromobenzene (see Section 2.1.1.7.), usually in a high-boiling solvent or by heating the neat components.1 4... 

However, they can also be prepared by metal exchange from alkali-metal phthalocyanines. If proton donors like hydrochloric acid, water or methanol are added to the reaction mixture of a freshly prepared alkali-metal phthalocyanine, metal-free phthalocyanines (PcH2) are formed (see Section 2.1.4.1,). If, on the other hand, the appropriate metal salt is added to a solution of an alkali-metal phthalocyanine, the product is the metalated compound (PcM) (see Section 2.1.6.). 

Electrochemical methods 78,79 and reactions under high pressure have also been investigated.80 Due to the high resonance stabilization of the macrocyclc, the formation of the phthalocyanine is strongly exothermic. Nevertheless, a high thermal activation and therefore usually a high temperature is necessary. 

Especially in the case of metal-free phthalocyanines, a template effect cannot be involved and the reaction has to pass via intermediates 4, 5 and 6 which have been isolated6,87,88 or like 7 which has only been postulated.89... 

A second reaction which is very often used for the preparation of phthalonitriles, although the yields are usually not reproducible, is the Rosenmund-von Braun reaction (see Houben-Weyl, Vol. E5, p 1460).106 107 Herein, a benzene derivative with a 1,2-dibromidc or 1,2-dich-loride unit is treated with copper(I) cyanide in dimethylformamidc or pyridine. During this reaction the formation of the respective copper phthalocyanine often occurs. This can be used as an easy procedure for the exclusive synthesis of copper phthalocyanines (see Section 2.1.1.7.),1 os-109 but can also lead to problems if the phthalonitrile is required as the product. For example, if l,2-dibromo-4-trifluoromethyl-benzene is subjected to a Rosenmund-von Braun reaction no 4-trifluoromethylphthalonitrile but only copper tetra(tri-fluoromethyljphthalocyanine is isolated.110... 

Both 4,5- and 3,6-disubstituted phthalonitriles are commonly used to prepare phthalocyanines with liquid crystalline properties. An example of the Rosenmund-von Braun reaction is shown below.107... 

Usually metal-free phthalocyanine (PcH2) can be prepared from phthalonitrile with or without a solvent. Hydrogen-donor solvents such as pentan-l-ol and 2-(dimethylamino)ethanol are most often used for the preparation.113,127 128 To increase the yield of the product, some basic catalyst can be added (e.g., DBU, anhyd NH3). When lithium or sodium alkoxides are used as a base the reaction leads to the respective alkali-metal phthalocyanine, which can easily be converted into the free base by treatment with acid and water.129 The solvent-free preparation is carried out in a melt of the phthalonitrile and the reductive agent hydroquinone at ca. 200 C.130 Besides these and various other conventional chemical synthetic methods, PcH2 can also be prepared electrochemically.79... 

Calcium phthalocyanine (PcCa) can be prepared by the reaction of calcium oxide with phthalonitrile58 or by the reaction of dilithium phthalocyanine and calcium chloride in ethanol.59... 

Tin phthalocyanines can be prepared using tin(II)110 or -(IV)154 chlorides. The reaction can be performed in 1-chloro-1 10,1 37,1 55 or 1-bromonaphthalene,154 starting from phthalonitrile110137154,155 or phthalic anhydride. In the second case, urea and ammonium molyb-date(VI) arc added.137 The central tin atom can also be introduced into metal-free phthalocyanine by the reaction with tin(IV) chloride in dimethylformamide.141 Treatment of PcSnCl2 with disodium phthalocyanine in refluxing 1-chloronaphthalenc forms a sandwich-like bis-(phthalocyanine) Pc2Sn.154... 

Antimony phthalocyanine can be prepared in a melt of antimony(III) chloride and phthalonitrile. The obtained product is of the formula [PcSb(Cl)2] SbClfi.164 PcSbX is formed by the reaction of metal-free phthalocyanine with antimony(III) chloride in l-chloronaphthalene59 or by the reaction of metal-free phthalocyanine with antimony(III) fluoride.165... 

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