Substituted phthalocyanines

LB films of 1,4,8,11,15,18-hexaoctyl-22,25-bis-(carboxypropyl)-phthalocyanine (2), an asymmetrically substituted phthalocyanine, were stable monolayers formed at the water—air interface that could be transferred onto hydrophilic siUca substrates (32—34). When a monolayer film of the phthalocyanine derivative was heated, there was a remarkable change in the optical spectmm. This, by comparison to the spectmm of the bulk material, indicated a phase transition from the low temperature herringbone packing, to a high temperature hexagonal packing. 

The increased solubility of substituted phthalocyanines (vide infra) enables more common purifications as used for other organic compounds. Usually the purification is done by chromatography either on alumina or silica gel, but recrystallization and extraction procedures can also be used. In some cases, the methods used for unsubstituted phthalocyanines can also be practiced, although the increased molecular weight accompanied by a reduced thermal stability makes sublimation more difficult.97 98 However, for substituted phthalocyanines, the stability towards acid may be reduced97 and, therefore, purification by treatment with sulfuric acid cannot generally be recommended. 

Although many attempts have been made to separate or exclusively synthesize one isomer of an unsymmetrically substituted phthalocyanine,72-89-296,297 the product mixture has been separated in only two cases.96 103,104 Besides the chromatographic separation of the statistical product mixture it is also possible to prepare exclusively the D4h isomer by use of steric hindrance of bulky substituents, e.g. 7-ferr-butylnaphthalene-l,2-dicarbonitrile only forms the respective An isomer of the tetra(to -butyl)-substituted 1,2-NcFe by heating in hexan-l-ol.73 Recently, some 1,8,1 5,22-substituted pure isomers have also been synthesized by the use of bulky substituents in 3-substituted phthalonitriles298,299 at low temperature (see Section 2.1.4.).94... 

Unsymmetrically substituted phthalocyanines can be prepared from two differently substituted phthalonitriles in a statistical condensation. It is obvious that a mixture of six different phthalocyanines (see p 738) can be obtained AAAB, ABAB (opposite type), AABB (adjacent type), ABBB and the products of the self-condensation of the respective phthalonitriles. If one of the phthalonitriles is substituted with bulky substituents, the yield of isomers with these groups in close vicinity can be reduced. In the following example no product of the self-condensation of tetraphenylphthalonitrile (BBBB type) can be detected. 

Unsymmetricaily substituted phthalocyanines are prepared from two differently substituted isoindolinediimines A and B, respectively. If one of the isoindolinediimines cannot undergo a self-condensation due to sterical hindrance, only a reduced number of different phthalocyanines is formed. 

Unsymmetrically substituted phthalocyanines 11 can be prepared out of two differently substituted phthalonitriles A and B, respectively. In the following example, one of the phthalonitriles is used in excess. 

Acylation of 22-(8-hydroxyoctyl)-25-methyl-l,4,8,ll,15,18-hcxaoctylphthalocyanine with ferrocenecarbonyl chloride in the presence of pyridine in dichloromethane at 25 C for 5 hours yields the corresponding 22-[8-(ferrocenecarbonyloxy)octyl]-substituted phthalocyanine in 38% yield.337... 

An easy approach to obtain amino-substituted phthalocyanines is the reduction of nitro groups, which are easily introduced into the macrocycle by condensation of the respective phthalonitrile. 

The redox potentials of zinc-substituted phthalocyanines are shown to be linearly dependent on the total Hammett substituent constant.837 In 1987, Stillman and co-workers used the absorption and magnetic circular dichroism spectra of the zinc phthalocyanine and its 7r-cation-radical species to assign the observed bands on the basis of theoretical calculations. The neutral and oxidized zinc phthalocyanine complexes with cyanide, imidazole, and pyridine were used with the key factor in these studies the stability of the 7r-cation-radical species.838 The structure of zinc chloro(phthalocyaninato) has been determined and conductivity investigated.839... 

Gregory, P. Thetford, D. (Zeneca). Poly-Substituted phthalocyanines. U S Patent 5486,274, January 23, 1996. 

Figure 13 Ring expansion of a haloboron(III) subphthalocyanine (49) to give an unsymmetrically substituted phthalocyanine, here the zinc(II) benzonaphthoporphyrazine (51).252,253 As usual, the product is...

The photobleaching kinetics for the zinc(II) complexes of several substituted phthalocyanines and analogues under a variety of conditions (e.g., aqueous media,265-267 organic solvents,230,235,265,266 polymer-bound266) have been reported. 

It should be noted that the basic reactions used to prepare phthalocyanine derivatives today are fundamentally those developed by Linstead and coworkers in the 1930s [52-54]. Due to the large number of substituted phthalocyanines described in the literature, space limitations mean that a detailed review of synthetic aspects cannot be provided here. The following discussion is concerned with the synthesis of lanthanide phthalocyanines via (i) template tetramerization of phthalonitrile with lanthanide salts, (ii) direct metalation of the metal-free ligands by the salts or (iii) metal exchange of a labile metal ion or ions for a lanthanide. 

The series of Zn(II) complexes with 1-amidino-3-aryl-substituted-thioureas [121], acetamidomalondihydroxymate [122], benzilbisthiosemicarbazone [123], novel fluorene-substituted terpyridine [124], per-fluoroalkoxy-substituted phthalocyanine [125], and 3-carboxylacetonehydroxamic acid [126] were synthesized. The behavior of these complexes was investigated by spectroscopic and electrochemical methods. 

Fig. 15. The electroluminescent efficiency versus number of monolayers or substituted phthalocyanine for the device shown in Fig, 14...

Fig. 17. Saturation current versus NCT gas concentration for a device incorporating eight monolayers of the asymmetrically substituted phthalocyanine molecule shown in the inseri (Baker et al., 1983)...

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