Dilithium phthalocyanine

Disodium phthalocyanine (PcNa2) can be prepared in the same way as the dilithium compound by reacting sodium pentoxide in pentan-l-ol with phthalonitrile. It is more sensitive towards moisture and even alcohol than the dilithium phthalocyanine and is readily demeta-lated.58... 

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... 

Lead(II) phthalocyanine can be prepared by heating lead(II) oxide with the respective phthalonitrile without solvent150-159 or in 1-chloronaphthatene.154 Addition of anhydrous lead(II) acetate to a solution of dilithium phthalocyanine in anhydrous alcohol gives a precipitate of lead phthalocyanine.59 Lead phthalocyanine can also be obtained by electrosynthesis.160... 

Arsenic phthalocyanine (PcAsCl) can be prepared by metal exchange starting from dilithium phthalocyanine and arsenic(lll) chloride in dimethylformamide.163... 

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. 

Dilithium phthalocyanines are readily converted to metal-free phthalocyanines on hydrolysis. To prepare 1,8,15,22-tetrasubstituted phthalocyanines 4 the corresponding 3-monosubstituted phthalonitriles 3 have to be used. 

In the preparation of lutetium(III) 2,9,16,23-tetra-ter -butylbis(phthalocyanine) from lutetium(III) acetate, dilithium phthalocyanine and dilithium 2,9,16,23-tetra-terr-butyl-phthalocyaninc in refluxing 1 -chloronaphthalene for one hour, only one of the phthalocyanine moieties carries all of the substituents (yield 20%).185... 

Chloroindium(III) phthalocyanine 16 can be synthesized from dilithium phthalocyanine 15 in 19% yield.432... 

Silver(II) phthalocyanine has been obtained by the action of silver nitrate on dilithium phthalocyanine in absolute alcohol at room temperature, or by the action of silver sulfate upon lead phthalocyanine in boiling 1-chloronaphthalene.496,561 ESR studies confirmed the presence of the paramagnetic d9 Ag ion, and for a frozen solution in 1-chloronaphthalene showed well-resolved nitrogen hyperfine lines. In the undiluted solid at room temperature, only a broad resonance was observed at g < 2.016. This may have been caused by aggregation.562... 

Oxidation of dilithium phthalocyanine Li2Pc affords a mono-lithium Pc rr-radical, LiPc, in which one unpaired electron resided in HOMO aiu n-orbital [23-25], ESR spectrum in chloronaphthalene solution was reported by Simon et al. [26], LiPc... 

Phthalocyanine itself is best prepared3 by self-condensation of phthalimidine, which is available from the reaction of phthalonitrile with ammonia. However, in many cases, direct metalation of the macrocycle cannot be achieved. Instead, metalation by means of dilithium phthalocyanine or a template reaction, whereby the macrocycle is formed around the metal using phthalonitrile (or one of its derivatives), must be employed for the synthesis of metallophthalocyanins. 

A portion of the product (0.5 g, 0.95 mmole) is dissolved in freshly distilled dry acetone (100 mL) and the solution is filtered. The filtrate is reduced in volume to about 10 mL, dry toluene/hexane, 49 1 (50 mL) is added, and the mixture is allowed to stand overnight to give crystals of the solvated product, which, after filtration and washing with a little toluene/hexane (49 1), are heated under vacuum at 250° for 2 hours to give pure dilithium phthalocyanine, 0.45 g (90%). Anal. Calcd. for C32H16N4Li2 C, 73.0 H, 3.04 N, 21.30. Found C, 72.8 H, 3.08 N, 21.10. 

Dilithium phthalocyanine is obtained as dark-blue crystals. The compound has high thermal stability, as is typical of many phthalocyanines. It is soluble in acetone, giving a deep-blue solution that deposits phthalocyanine when in contact with even trace amounts of water. The material is also soluble in ethanol and tetrahydrofuran, but it is insoluble in diethyl ether, hexane, or chloroform. Solutions of the dilithium complex in ethanol react rapidly and quantitatively with a variety of metal salts to give the metallophthalocyanines, which precipitate, in very pure form, from solution. The electronic spectrum contains the bands (acetone solution) 370 (e = 24,800), 596 (e = 17,300), 630 (e = 16,100), 655 nm (e = 11,100). 

The alkali metal phthalocyanines are, with the exception of the dilithium derivative, fairly insoluble in most organic solvents. The dilithium complex is unique in being soluble in a wide range of organic solvents including alcohol and acetone 11). All the complexes are readily demetallated by dilute aqueous acid. Dilithium phthalocyanine is rapidly demetallated by cold water 11), while disodium phthalocyanine is more resistant to hydrolysis, reacting slowly with hot water. The dipotassium derivative is said to be more readily demetallated than the sodium complex, perhaps because of its larger size 10). 

Dilithium phthalocyanine was originally prepared from lithium amyl-oxide and phthalonitrile in boiling amyl alcohol 11), but may also be prepared from lithium hydride 53) or lithium metal 214) and phthalonitrile. It is readily purified by recrystallization from acetone. A monolithium derivative, presumably lithium hydrogen phthalocyanine, is formed when a deficiency of lithium or lithium salt is used in these reactions. It is a black insoluble compound of unknown structure 11). The high solubility of the dilithium complex makes it a very useful intermediate in double decomposition reactions. Many comparatively unstable metal phthalocyanines can be formed by the reaction of dilithium phthalocyanine and the appropriate metal salt in a solvent such as acetone, dimethylformamide, or quinoline 11, 119, 120). 

This complex may be prepared from quicklime and phthalonitrile (10, 88) or from dilithium phthalocyanine and calcium chloride in ethanol (11). It does not sublime. 

Mercury(II) phthalocyanine is prepared by the interaction of mercuric chloride with dilithium phthalocyanine in absolute alcohol (11). It is readily demetallated in concentrated sulfuric acid and in boiling chloronaphthalene, and will not sublime (111, 226). 

Arsenic trichloride reacts with dilithium phthalocyanine in dimethyl-formamide to yield chloroarsenic phthalocyanine 808), which does not react with silver ions in pyridine. Its absorption spectrum has been recorded (Section V,B), but little else is known of the complex. 

Chlorotitanium(III) phthalocyanine is formed by the reaction of titanium trichloride with dilithium phthalocyanine in boiling quinoline in the absence of air. This d1 complex has a magnetic moment of 1.79 B.M. (see Section VI,D) 341). It is stable to air oxidation in the solid state but is oxidized in solution. The oxidation product is oxytitanium(IV) phthalocyanine (titanyl phthalocyanine). This latter diamagnetic complex may also be prepared by the reaction of titanium tetrachloride dipyridinate and phthalonitrile at 270°C followed by sublimation at 400°C/10 6 mm 213). Titanium tetrachloride reacts with phthalonitrile to yield, after recrystallization from sulfuric acid, dihydroxytitanium(IV) phthalocyanine 820). 

The reduction of ferrous phthalocyanine with lithium benzophenone in tetrahydrofuran yields the solvated lithium phthalocyanine ferrate(I) (having one unpaired electron) and dilithium phthalocyanine ferrate(O) (diamagnetic) (340). The reduction of (LXXI) with alkaline sodium boro-hydride in methanol has also been studied 48). 

A quinoline-soluble thorium phthalocyanine is formed in the reaction of thorium tetrachloride with phthalonitrile at 260°C 378), but no analytical data were reported. An ill-characterized sulfonated derivative has also been recorded 119). Uianyl phthalocyanine (U02Pc) has been observed as the product of the reaction of bis(dimethylformamide)uranyl acetate with dilithium phthalocyanine 119, 120), and of the reaction of uranyl acetate with phthalic anhydride 187, 233). Recently, however, Bloor et al. 31) reported that uranyl phthalocyanine formed by the reaction of uranyl chloride and phthalonitrile in dimethylformamide at 180°C has different infrared and visible absorption spectra from those originally quoted 187, 233) and they conclude, on the basis of infrared data, that the uranyl phthalocyanine obtained by previous workers was essentially a mixture of a metal-free phthalocyanine and inorganic uranium salts. 

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