Macrocycles Phthalocyanines

Large macrocyclic phthalocyanines can be obtained from the condensation reactions of 2,5-diamino-l,3,4-thiadiazole <2006SC1801,2006MI837,20010L2153>. Diaminothiadiazole reacts with 5- z/-butyl-l,3-diiminoisoindoline in 2-ethoxy-ethanol at 135 °C for 24 h to give macrocycles 107 and 108 in 54% and 15% yields, respectively <20010L2153>. 

The macrocyclic phthalocyanine ligand will form a complex Pt(phthalocyanine).1106 The crystal structure shows two polymorphs present because of molecular packing.1107 The platinum is in a square planar coordination geometry with a mean Pt—N distance of 1.98 A. The complex can be partially oxidized with iodine to give conducting mixed valence solids.1108 Eighteen fundamental and overtone combination bands are observed in the resonance Raman spectrum of platinum phthalocyanine, and from this data the symmetry of the excited singlets are found to be Dy.. Qlv or D2.1109... 

The macrocycle phthalocyanine contains 8 N atoms, but usually only the four N-atoms on the inner side of the cycle are able to coordinate. In fact, in most cases the synthesis of phthalocyanine is realized in the presence of a metal ion as the template. It is also possible to attach various substituents on the phthalocyanine macrocycle. As for porphyrin, when coordinating to a metal ion, the H-atoms of the two NH groups on the inner side of the phthalocyanine cycle are replaced. The incorporation of metal porphyrin and phthalocyanine complexes into porous crystals has been gaining increasing interest. The properties of the complexes located in zeolite channels or cages are usually different from those of the compounds in solution, and they may find applications in areas such as catalysis, photochemistry, electrochemistry, and biomimetics. 

ARTIFICIAL PLANAR MACROCYCLES - PHTHALOCYANINES AND OTHER CYCLIC SYSTEMS... 

Artificial Planar Macrocycles - Phthalocyanines and Other Cyclic Systems... 

Halide complexes are also well known but complexes with nitrogen-containing ligands are rare. An exception is the blue phthalocyanine complex formed by reaction of Be metal with phthalonitrile, 1,2-C6H4(CN)2, and this affords an unusual example of planar 4-coordinate Be (Fig. 5.5). The complex readily picks up two molecules of H2O to form an extremely stable dihydrate, perhaps by dislodging 2 adjacent Be-N bonds and forming 2 Be-O bonds at the preferred tetrahedral angle above and below the plane of the macrocycle. 

Macrocyclic effect and specific character of complex formation with phthalocyanins 97MI8. 

Phthalocyanines (Pc) consist of a planar macrocycle with an 18tt-electron system. 

The solubility of phthalocyanines in common organic solvents can be increased by introducing bulky or long-chain substituents either in the periphery of the macrocycle or, if the... 

Thallium phthalocyanine (PcT12) can be obtained by heating phthalonitrile with an inter-metallic alloy of indium and thallium in an evacuated glass ampule.145 The structure of this compound is unique among metal phthalocyanines as the two thallium cations occupy two opposite corners of an octahedron, which is formed by the thallium cations and the four iso-indolinc nitrogen atoms facing the center of the macrocycle.147 Another unusual type of phthalocyanine can be prepared by heating phthalonitrile with thallium metal.148 It was identified as a bicyclic thallium(III) phthalocyanine (Pc3/2T1).14S... 

Phthalocyanines are commonly very stable compounds. Therefore, the macrocyclic structure of these compounds is maintained during most of the chemical reactions. If reaction conditions are harsh enough to break bonds ofthe macrocyclic skeleton, usually defined or undefined97-361 products of minor interest are obtained. Usually, however, reactions on phthalocyanines can be regarded as syntheses of other phthalocyanine compounds. 

Almost every metal atom can be inserted into the center of the phthalocyanine ring. Although the chemistry of the central metal atom is sometimes influenced in an extended way by the phthalocyanine macrocycle (for example the preferred oxidation state of ruthenium is changed from + III to + II going from metal-free to ruthenium phthalocyanine) it is obvious that the chemistry of the coordinated metal of metal phthalocyanines cannot be generalized. The reactions of the central metal atom depend very much on the properties of the metal. 

This compound has been investigated by several groups,379- 384 but due to its practical insolubility it has not been fully characterized. Another approach to obtain phthalocyanine network polymers is with the use of crown ethers385 or other groups like di oxy -para-p h enyle n e3 8 6 as bridging units between the macrocycles. Some attempts to obtain metal phthalocyanine substructures arranged as ladder polymers have also been proposed (see below).344... 

Bicyclic phthalocyanines possess an unusual skeleton built from three halves of a normal phthalocyanine macrocycle, arranged like a propeller. Such compounds are formed by treating phthalonitrile at low pressure and high temperature (0.1 atm, N2,210 C, 1-2 d) in the presence of thallium148 or indium (yield 5%).146... 

Octasubstituted bis(phthalocyanines) 22 have been reported in the case of lanthanide elements. They contain eight bidentate substituents bound to the macrocycle.159,194... 

Although the substitution of a preformed phthalocyanine always leads to a complex mixture of more- or less-substituted products, the reaction is of major industrial importance. Besides the chloro- and bromocopper phthalocyanines, also polysulfonated phthalocyanines, which are used as water-soluble dyes, are produced by the reaction of copper phthalocyanine with the respective reactant. While typical aromatic reactions of the Friedel-Crafts type are also possible,333 direct nitration of the macrocycle commonly results in oxidation of the phthalocyanine. However, under mild conditions it is possible to introduce the nitro group directly into several phthalocyanines.334... 

Other examples of the synthesis of phthalocyanines by conversion of substituents of the macrocycle by hydrolysis are given below,... 

The oxidation of the macrocycle in phthalocyanines does not generally lead to stable molecules. One-electron oxidations of the macrocyclc(s) in bis(phthalocyanines) leading to species which can be isolated have been carried out chemically or electrochemically,... 

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. 

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