Phthalocyanines, polymeric, synthesis

Table 2. Synthesis of Phthalocyanines by Conversion of Substituents at the Central Metal Giving (Oligo)Polymerization...

Synthesis and properties of polymeric phthalocyanines and their metal derivatives. A. A. Berlin and A. I. Sherle, Inorg. Macromol. Rev., 1971,1, 235-270 (129). 

We have demonstrated a new class of effective, recoverable thermormorphic CCT catalysts capable of producing colorless methacrylate oligomers with narrow polydispersity and low molecular weight. For controlled radical polymerization of simple alkyl methacrylates, the use of multiple polyethylene tails of moderate molecular weight (700 Da) gave the best balance of color control and catalyst activity. Porphyrin-derived thermomorphic catalysts met the criteria of easy separation from product resin and low catalyst loss per batch, but were too expensive for commercial implementation. However, the polyethylene-supported cobalt phthalocyanine complex is more economically viable due to its greater ease of synthesis. 

Most reported phthalocyanine derivatives (sulfo-, nitro-, amino-, triphenylmethyl-, polymeric, etc.) are copper complexes, although at present the synthetic chemistry of other d- and /-metal Pc derivatives is being rapidly developed (Examples 30-36) [5,6,116-118]. Some of them (in particular, copper phthalocyanine sulfonic acids) are of industrial interest because of their usefulness as dyes. Phthalocyanine sulfonic acids themselves are prepared both by urea synthesis from sulfonated phthalic anhydride and by the sulfonation of the phthalocyanine [6], Some substituted metal phthalocyanines can be obtained by chemical or electrochemical reduction [118e]. Among a number of reported peculiarities of substituted phthalocyanines, the existence of three electronic isomers for magnesium derivative PcMn was recently confirmed [118f]. 

The well known synthesis of low molecular phthalocyanines Pc, 2) starts from phthalic add derivatives like 1,2-dicyanobenzene, 1,3-diiminoisoindolenine and jAthalic anhydride The yield of metal free or metal containing Pc is often high (80-100%). By starting with a Wfunctional material like 1,2,4,5-tetracyanobenzene (TCB) or pyromellitic dianhydride (PMDA) a polymeric phthalocyanine (polyPc) (86) must be formed under the same conditions (Eq. 40). But the determination of structure and molecular weight is very difficult. Byproducts may be formed and the resulting polymers are often less soluble. But structure investigations are very important to correlate structure and property. 

In another synthesis the phthalocyanine molecules are polymerized via groups at the end of the side chains (217). This polymer also shows hardly any luminescence at 4.2 K. 

Polymeric phthalocyanines (Chap. 5.2) indude a great variety of properties. The construction of electrical devices or catalysts for spedal use is most hopeful. But all these applications depend on the reproduribility of well defined structural uniform polymers. Preparative work must help to standardize synthetic procedures and to investigate structures. The well reproducible in situ synthesis of thin layers of pure polymeric phthalocyanines from the gas phase opens a way for electrocatalysis and visible light energy changing devices. Another new kind of preparation goes via prepolymers which may be converted to mechanically and thermally stable, infusible polymers. 

The synthesis and characterization of coordination polymers was supported by the U.S. Air Force in a search for materials that exhibited high thermal stabilities. However, attempts to prepare stable, tractable coordination polymers that simulate the exceptional thermal and/or chemical stability of model monomeric coordination compounds such as copper(II) ethylenediaminobisacetylacetonate or phthalocyanine have been disappointing ". Typically, only short chains are formed, and the thermally stable monomers lose most of their stability when linked by the metals into polymeric units. The principles in designing coordination polymers are ... 

While the types of MCMs described earlier have already received comparatively wide popularity in polymerization practice, polymers based on metal-containing monomers of the chelate type have only been prepared more recently. The methods of assembly of such MCMs, i.e. the simultaneous formation of the ligand and the corresponding complex, have been substantially developed. The synthesis of MCMs from /7-aminostyrene, 2-formylpyrrole and Cu(II) or Co(III) salts is an example of such a method. The last approach is especially characteristic of the preparation of MCMs with macrocyclic chelate nodes, in particular, from porphyrins, phthalocyanines and other macrocycles with exocyclic multiple bonds. It is worth noting that traditional methods of chelation are used for preparing MCMs when scientists want to ensure strong multicenter fixation of metals into monomer molecules, and, thus, into (co)polymers. 

These are the same chelate-type MCMs, but with tetradentate coordination (Table 4-1). Moreover, MCMs with a small strained structure (vinylimine, epoxide) have already been considered above. By considering MCMs with macrocycles in a separate section, we wish to focus attention on monomers of this type because of their widespread use in polymerization practice, especially, porphyrin and phthalocyanine derivatives. As we know, such macrocycles are n-conjugated planar tetradentate ligands and capable of forming rather stable chelates with almost all metals. A basic method of MCM synthesis is based on the incorporation of metal ions into a window of macrocycles completed by an exocyclic multiple bond [45 8]. Examples are 74-76. 

A linear phthalocyanine containing polyesters 46 has been described [128,129], Recently, a linear polymeric phthalocyanine 47 prepared in a multistep synthesis with an iptycene architecture was briefly described [130]. At first two differently substituted l,3-dihydro-l,3-diiminoisoindolenines were statistically reacted. In the mixture of phthalocyanines obtained, the ethylenedioxythiophene part is introduced and the bis(ethyleneoxythiophene) oppositely substituted phthalocyanine was isolated by flash chromatography. Afterwards the thiophene parts in the phthalocyanine were electrochemically polymerized to obtain 47. 

Recently, Wynne and co-workers [1,2] and Marks and co-workers [3-6] described the synthesis and characterization of inorganic-organic polymers, in which a metallic or pseudometallic element alternates with a linear-chain bridging atom, like oxygen or fluorine. The metallic or pseudometallic element is usually the centr atom of a phthalocyanine system, and the bridge-stacked polymeric structure is rigid. These derivatives are electrical conductors after iodine oxidation. 

Several types of porphyrin and phthalocyanine ligand modification have been performed to create a new family of electrochemically polymerizable complexes. The most commonly used porphyrins are the amino " hydroxy methoxy ° ° , vinyl- and other " substituted macrocyclic complexes (see examples in Figure 8.13). In the case of phthalocyanine, tetra-amino-substituted macrocycle was exclusively and intensively developed. Studies of these complexes have focused on the electrochemical synthesis and characterization of conductive polymeric or copolymeric materials. 

Besides their potential applicability as NLO materials noncentrosymmetri-cal phthalocyanines with different substituents on adjacent pairs of isoindole units promise intriguing new aspects in phthalocyanine chemistry polymeric phthalocyanines without crosslinking could lead to linear polymers, controlled binding of the phthalocyanine ring to a substrate could improve the synthesis of novel catalysts [188] and the preparation of highly ordered thin films should be possible [189]. 

---