Polymers of Phthalocyanines

Network Planar Polymers of Phthalocyanines as Catalysts or Adsorbents... 

Electrodes of two-dimensional sheet polymers of phthalocyanines prepared by in situ reaction of tetracyanobenzene with thin metal films were prepared and characterized in their photoelectrochemical characteristics. Anodic photocurrents were detected, characterizing these films as n-type semiconducting materials. It was also found that such films could be reduced at more positive potentials than unsubstituted phthalocyanines. This change when compared to films of divalent unsubstituted phthalocyanines is caused by unreacted CN groups that were found in the films " . Such films therefore can be looked at as substituted phthalocyanines with electron-withdrawing CN groups which explains their photoelectrochemical characteristics. 

In contrast to phthalocyanines (tetra- or octasubstituted) in which the isoindoline units carry all the same substituents, reports of phthalocyanines with lower symmetry, which have been prepared by using two different phthalonitriles, have rarely appeared. This is due to the problems which are associated with their preparation and separation. For the preparation of unsymmetrical phthalocyanines with two different isoindoline units four methods are known the polymer support route,300 " 303 via enlargement of subphthalocyanines,304 " 308 via reaction ofl,3,3-trichloroisoindoline and isoindolinediimine309,310 and the statistical condensation followed by a separation of the products.111,311 319 Using the first two methods, only one product, formed by three identical and one other isoindoline unit, should be produced. The third method can be used to prepare a linear product with D2h symmetry formed by two identical isoindoline units. For the synthesis of the other type of unsymmetrical phthalocyanine the method of statistical condensation must be chosen. In such a condensation of two phthalonitriles the formation of six different phthalocyanines320 is possible. 

Hanack has reviewed a number of phthalocyanine and tetrabenzopor-phyrin shish-kebab porphyrin polymers (102). 

The cobalt(II)15 and zinc(II)16 complexes of phthalocyanine(Pc), octcyano-Pc, and tetrasulfon-ato-Pc incorporated in poly(4-vinylpyridine-co-styrene) or Nafion films coated on graphite have also been examined as catalytic devices for dihydrogen electrogeneration in phosphate buffer. These catalytic systems were strongly suggested to be dominated by the electron transfer within the polymer matrix. The best catalytic film is that constituted of the nonsubstituted Con-Pc complex in poly(4-vinylpyridine-co-styrene), giving a turnover number of 2 x 10s h-1 at an applied potential of —0.90 V vs. Ag Ag Cl. 

It has long been known (93) that cobalt(II) complexes of phthalocyanines interact with molecular oxygen. The water-soluble tetrasulfonato derivative of the parent phthalocyanine selectively and catalytically oxidizes 2,6-di-tert-butylphenol to the benzoquinone and the dipheno-quinone in both homogeneous solution (94) and when polymer-supported (95). The active intermediate in the catalytic cycle is proposed to be the (as expected) mononuclear dioxygen complex of the cobalt-tetrasulfonatophthalocyanine system (92). It has been proposed that the formation of a peroxo-bridged dinuclear complex is responsible for the deactivation of the cobalt(II)-tetrasulfonatophthalocyanine system, since such a dinuclear system would be unable to further bind and activate dioxygen (96). Such deactivation results, ultimately, in loss of the catalyst and low turnover ratios. 

In this context it is interesting to note that benzonitrile, Ph—C=N, trimerizes to a triazine on a Raney nickel surface. It was assumed that Jt-bonded nitriles were involved in the reaction mechanism.10 This reaction resembles the well-known template synthesis of phthalocyanine complexes from phthalodinitrile. Formation of linear polymers [—C(R)—N—] occurs on heating aryl or alkyl cyanides with metal halides.11... 

Several polymers of Ni and Cu-phthalocyanine appeared to be more active than the corresponding monomers, and this was correlated with the thermal activation energy of the electrical conductivity. A complicating factor was that the H2 to C02 ratio was always smaller than one with the polymers, which means that part of the hydrogen was absorbed by the polymer, a phenomenon we have encountered earlier in the section on hydrogen activation. 

Similar to the cases in other small molecules and polymers, most materials composed of phthalocyanine compounds are revealed to work as p-type semiconductors for OFET applications with only few phthalocyanine materials as n-type semiconductors and even less as ambipolar ones. Among the p-type tetrapyrrole semiconductors, monomeric phthalocyanine compounds hold all the trumps with only a few double- and triple-deckers together with some porphyrin derivatives having been reported. 

In addition, the polymers of intrinsic microporosity (PIMs), such as phthalocyanine networks and the Co phthalocyanine network-PIM (CoPc20), display high specific surface area, as confirmed by the N2 adsorption isotherm at 77 K, and by the adsorption of small organic probe molecules from aqueous solutions at 298 K [236], This material is basically microporous with an increased concentration of effective nanopores. 

Physical incorporatiem of phthalocyanines and porphyrins in polymers was mentioned in Chap. 2.1.1 and 2.1.2. Moreover, photovoltaic properties of Schottky bavier solar cells were checked by dispersing metal free Pc in a polymer binder At peak solar power (135 mW/cm ) a power conversion efficiency of 1,2% has been obtained. 

In an early investigation poly(4-vinylphthalic add anhydride) was converted with urea and CuQ to a polymer copper phthalocyanine . This polymer decomposes at 583 K. Because of the unsolubility, it was only possible to detect many unreacted carboxyl groups in the polymer. 

Some authors describe the covalent polymer bindii of phthalocyanines Co(II)-tetraammophthalocyanine (12 c) was coupled with cyanuric chloride to the amino groups of crosslinked aminated polystyrene or polyacrylamide (with aniline substituted groups) to get (45) and (46) >. 

Functionalized alkoxy derivatives of phthalocyanine complexes have been used to prepare polymeric PC materials and a number of studies have investigated the physical and mesomorphic properties of these and related polymers.300-306... 

Polymerization of phthalocyanines in water occurs for derivatives substituted with oligo (ethylene oxide) side-chains (27c).167 168 In the lyotropic mesophases in water supramolecular polymers are present, and a comparative aggregation study between tetraphen-ylporphyrins and phthalocyanines proved the polymerization of the phthalocyanines to be stronger.168 The strong arene—arene interactions and the flatness of the aromatic core in the phthalocyanines causes them to aggregate more strongly, also mediated by the additional hydrophobic effect. 

Scheme 4.1 Synthesis of phthalocyanine-based sheet polymer 2.

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