Phthalocyanine Metal Complexes

Figure 8.4 The structure of metal-phthalocyanine complexes, with increased complexity adapting to the requirement of different metal ionic species.

Metal phthalocyanine complexes may be obtained by one of the following methods ... 

The use of heterogeneous catalysts in the synthesis of urethanes from aliphatic and aromatic amines, C02 and alkyl halides has been explored only recently. Titanosilicate molecular sieves [60a], metal phthalocyanine complexes encapsulated in zeolite-Y [60a], beta-zeolites and mesoporous silica (MCM-41) containing ammonium cations as the templates [60b, c], and adenine-modified Ti-SBA-15 [60d, e] each function as effective catalysts, even without any additional base. 

Fig. 1 Schematic energy levels of the d orbitals in square-planar coordination of 3d metal phthalocyanine complexes. The ordering of the energy levels can be changed except for the highest orbital. The labels on the right are the irreducible representation in the D41, point group...

Metal phthalocyanine complexes are also frequently used as autoxidation catalysts (see Section II.B.2). They have generally been found to be more active than the corresponding stearates or acetylacetonates. Thus, Uri145 compared the catalytic activity of a series of transition metal stearates with the corresponding metal phthalocyanines in the autoxidation of methyl linoleate. The phthalocyanine complexes afforded faster rates of oxidation. In addition, the phthalocyanine ligand is stable and is not easily destroyed under autoxidizing conditions. Interest in metal phthalocyanine catalysts has also been stimulated by their resemblance to the metal-porphyrin structures contained in many oxidative enzymes (see Sections II.B.2 and V). 

One of the first examples of a metal or metal salts facilitating the formation of a macrocycle was the self-condensation of o-phthalonitrile to give metal phthalocyanine complexes from which the free ligand was easily displaced (89) ... 

In addition, the electronic spectrum of uranyl superphthalocyanine 160 is significantly different from those of known metal phthalocyanine complexes... 

Reactions of the uranyl superphthalocyanine complex 160 with anhydrous metal salts (e.g. C0CI2, NiClj, FeClj, CuClj, ZnClj, SnClj, and PbCl2) also results in a ring contraction. In this case, the corresponding metal phthalocyanine complexes are formed (Scheme 24) [132, 133], These contraction reactions indicate... 

The porphyrins constitute another class of nitrogen donor ligands which favor Ag(II) over Ag(I). Their macrocychc stmeture provides strong in-plane ligand fields, which facilitate oxidation of the metal. Phthalocyanine complexes of Ag(II) are very stable and can be oxidized electrochemically to Ag(III) further oxidation gives a Ag(III) phthalocyanine cation radical. The oxidation of Ag(I) complexes of sulfur macrocycles also leads reversibly to Ag(II) complexes. ... 

Figure 4.13 Molecular structures of macrocyclic metal complexes metal bis(glyoximate), metal tetraazaanulene and metal phthalocyanine complexes...

The hybrid metal phthalocyanine complexes may find application for specific pollution control processes such as S02 stack-gas scrubbing, post-Klaus plant scrubbing of H2S and S02, sweetening of sour oil-refinery wastes, odor and corrosion control in wastewater facilities, and the elimination of excess rocket fuel wastes. 

Boyce, S. D., M. R. Hoffmann, P. A. Hong, and L. M. Moberly (1983), Catalysis of the Autoxidation of Aquated Sulfur Dioxide by Homogeneous Metal-Phthalocyanine Complexes, Environ. Sci. Technol. 17, 602-611. 

Transition metal complexes of phthalocyanine encaged in faujasite type zeolites have been reported as efficient catalysts in the oxidation of alkanes at room temperature and atmospheric pressure [6-13]. These catalysts constitute potential inorganic mimics of remarkable enzymes such as monooxygenase cytochrome P-450 which displays the ultimate in substrate selectivity. In these enzymes the active site is the metal ion and the protein orientates the incoming substrate relative to the active metal center. Zeolites can be used as host lattices of metal complexes [14, 15]. The cavities of the aluminosilicate framework can replace the protein terciary structure of natural enzymes, thus sieving and orientating the substrate in its approach to the active site. Such catalysts are constructed by the so-called ship in a bottle synthesis the metal phthalocyanine complexes are synthesized in situ within the supercages of the zeolite... 

The crystallization of zeolites and molecular sieves with metal complexes represents a fresh strategy for the synthesis of these materials as well as a novel method for encapsulation of metal chelate complexes. We have shown that several first row tranistion metal phthalocyanines complexes can be encapsulated in X and A type zeolites by synthesizing the zeolite around the metal complex. Preliminary results indicate the concentration and type of phthalocyanine complex modify the crystallization of X type zeolites. The extension of this method to other metal chelate complexes and molecular sieves is currently under investigation. 

Phthalonitrile was reduced at controlled potential in alcoholic solution at a C cathode in a two-compartment cell in which cathode and anode were separated by a Nafion cation-exchange membrane. The anolyte contained metallic salts such as CUSO4, NiS04, etc. The products formed in the cathode compartment were metal phthalocyanine complexes. Low yields were obtained when the metal ions were placed into the cathode compartment. The phthalonitrile radical anion formed by a 1-electron transfer was invoked as being important in the cyclization process leading to the metal complexes. Several intermediates... 

P-12 - Effects of molecular confinement on structure and catalytic behaviour of metal phthalocyanine complexes encapsulated in zeolite-Y... 

Metal phthalocyanine complexes (MPc M = V, Co and Cu) encapsulated in zeolite-Y were prepared by in-situ ligand synthesis and characterized by chemical and thermal analyses and FT-IR, diffuse reflectance UV-vis and EPR spectroscopic techniques. The studies provided evidence for the encapsulation of MPc inside the supercages of zeolite-Y. The Pc moiety distorts from square planarity as a consequence of encapsulation. The encapsulated complexes exhibited enhanced styrene epoxidation activity with /e/-/-butylhydroperoxide compared to the neat complexes in homogeneous medium. The activity and product selectivity of the encapsulated complexes varies with the central metal atom. 

In organic solar cells consisting of zinc phthalocyanine and a perylene pigment it was possible to raise the short-eircuit eurrent by a factor of 1.5 when increasing the partial pressure of oxygen by a factor of three in comparison to that of ordinary atmosphere. The structure of a metal phthalocyanine complex is shown in Figure 1.15. 

Metalloporphyrins 3 and metal phthalocyanine complexes 4, as well as the metal-free ligands, commonly engage in aromatic-aromatic interactions. 

Hoffmann M. R. and J. O. Edwards (1975) Kinetics of the oxidation of sulphite by hydrogen peroxide in acidic solution. Journal of Physical Chemistry 79, 2096-2098 Hoffmann, M. R. and B. C. H. Lim (1979) Kinetics and mechanism of the oxidation of sulfide by oxygen Catalysis by homogeneous metal phthalocyanine complexes. Environmental Science and Technology 13, 1406-1414... 

A more recent focus of attention has been the oxidation reactions with O2 in the presence of so-called enzyme mimics [15, 58 - 71]. The most recent discoveries in connection with the selective partial oxidation of nonactivated alkanes over metal phthalocyanine complexes (MPc) enclosed in faujasite super-cages are very promising and many potential applications for these inorganic simulations of enzymes, for example of the natural monoxygenase enzyme cytochrome P 450 are possible. 

Electrocatalytic reduction of oxygen molecules was observed with graphite electrode coated with PXV-PSS complex. With respect to oxygen reduction, the catalytic activity of metal porphyrin complexes or metal phthalocyanine complexes adsorbed on the graphite surfaces has been reported by many workers and the mechanism was elucidated by using the rotatii disk or rotatii rii -disk voltammetry25.26 there are a few reports concernii the activity of electrode coated with... 

In another approach [77] (Scheme 31) 4-nitro substituted dimethylphthalate 118 was reacted with fluorinated alcohol in DMF in the presence of NaH at room temperature to give 4-fluoroalkoxy substimted diester 119. It was then converted to 4-fluoro-alkoxy substituted phthalic anhydride 120, which was directly used in template cyclotetramerization with metal acetates (Mg", Co", Zn") or chlorides (Cu, Fe" , Al ") by urea melt method (urea, ammonium molybdate, NH4CI) to give directly the corresponding p-tetrasubstituted metal phthalocyanine complexes (yields 7-26 %). 

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