Cobalt phthalocyanine structure

At present, synthetic routes to more than 40 metal complexes other than the copper complex are known. Apart from a cobalt phthalocyanine pigment (P.B.75) which was introduced to the market just recently, none of the resulting products, however, has stimulated commercial interest as a pigment. Nickel complexes, however, are found in reactive dyes, while cobalt complexes of this basic structure are employed as developing dyes. 

We are still further from being able to explain the anodic activity of the CoTAA complex. The cobalt phthalocyanine, which is structurally identical with CoTAA in the inner coordination sphere, is completely inactive in the catalysis of anodic reactions. It therefore looks as if the central region is not exclusively responsible for the anodic activity. On the other hand, the fact that CoTAA is inactive for the oxidation of H2 points to n orbitals of the fuel participating in the formation of the chelate-fuel complex. A redox mechanism (cf. Section 5.2) can be ruled out because anodic oxidation proceeds only in the region below the redox potential of CoTAA (i.e. at about 600—650 mV). 

Cobalt complexes find various applications as additives for polymers. Thus cobalt phthalocyanine acts as a smoke retardant for styrene polymers,31 and the same effect in poly(vinyl chloride) is achieved with Co(acac)2, Co(acac)3, Co203 and CoC03.5 Co(acac)2 in presence of triphenyl phosphite or tri(4-methyl-6- f-butylphenyl) phosphite has been found to act as an antioxidant for polyenes.29 Both cobalt acetate and cobalt naphthenate stabilize polyesters against degradation,73 and the cobalt complex of the benzoic acid derivative (12) (see Section 66.4) acts as an antioxidant for butadiene polymers.46 Stabilization of poly(vinyl chloride)-polybutadiene rubber blends against UV light is provided by cobalt dicyclohexyldithiophosphinate (19).74 Here again, the precise structure does not appear to be known. 

The principal chromophores in pseudo sulfur dyes are copper and cobalt phthalocyanines, e.g., in C.I. Sulphur Green 25 (16), and the perylene tetracar-boxylic diimide structure in C.I. Sulphur Red 14 [81209-07-6] and C.I. Solubilised Sulfur Red 11 [61969-41-3] (17). In contrast to the sulfur dye made from Cu phthalocyanine, the cobalt derivative can be applied with dithionite. 

Similar behavior has been very recently observed in cobalt phthalocyanines bearing dendritic substituents [122], In 47, Co is oxidized in methanol in a mono-electronic reversible wave, whereas in 48 no clear oxidative wave is observed, suggesting that the electroactive core is encapsulated in the dendritic structure. The ability of the Co-phthalocyanine core of 47 and 48 to catalyze oxidation of 2-mer-captoethanol in the presence of oxygen was also investigated. The two compounds exhibit similar catalytic activity, indicating that the dendritic structure does not hinder penetration of small molecules 48 showed, however, an enhanced catalytic stability which was ascribed to the encapsulation of the core. 

It is clear that a core of four nitrogen atoms in the coordination center is crucial for active CCT. Replacement of two nitrogen atoms with oxygen (23— 26, 29—31) or sulfur (28) essentially shuts down the ability of LCo to abstract hydrogen from free radicals. Compound 28 is particularly interesting because of the similarity of molecular structure of this chelate to cobalt phthalocyanines, which are known to be good CCT catalysts. 

The ID growth along steps is, however, not hmited to metal overlayers. Recently also cobalt phthalocyanine (CoPc) has been found to nucleate along the steps of the vicinal Au(7 8 8) surface [152] (Fig. 18). This particular surface shows also remains of the herringbone structure of Au(l 11) and indeed a weak tendency for preferential adsorption of the CoPc on the fee domains on the terraces has also been found. 

Examples of building up large molecules inside a zeolite structure via a reaction were frequently reported under the term ship-in-the-bottle synthesis . For instance, very early Romanowski et al. [844] and, somewhat later, Schulz-Ekloff et al. [845] produced phthalocyanines in faujasite-type zeolites and investigated the pro ducts, inter alia, by IR spectroscopy. Cobalt-phthalocyanine encapsulated in zeolite EMT was prepared and, inter alia, characterized via IR spectroscopy by Ernst et al. (cf. [846] and references to related work therein). A number of typical bands of CoPc-EMT in the mid infrared (1600-1200 cm ) were observed and interpreted. 

Figure 3.4. Molecular structure of cobalt phthalocyanine (CoPc), cobalt tetramethoxy phenylporphyrin (CoTMPP), and cobalt tetraazaannulene (CoTTAA).

ArgueUo J, Magosso HA, Ramos RR, Canevaii TC, Landers R, Pimentel VL, Gushikem Y (2009) Structural and electrochemical characterization of a cobalt phthalocyanine bulk-modified SiO /SnOj carbon ceramic electrode. Electrochim Acta 54 1948-1953... 

Figure 9 (a) Molecular structure of the cobalt phthalocyanine molecules containing fonr crown ethers, (b) STM image of a monolayer... 

In addition to hydrogen bonding, other types of noncovalent interactions, such as perfluorophenyl-phenyl interactions, are very well suited for self-assembly purposes. The perfluorinated cobalt phthalocyanine (F16Co5) molecules do not form an ordered structure when deposited on Au(lll) under UHV [131,132]. This disorder and the lack of submolecular resolution are in contrast to the behavior of the protonated complex, which is... 

Fig. 18 a CVs, b SWV of CoPc3 in DCM/TBAP, c CVs and d SWV in DMSO/TBAP at various scan rates on a Pt working electrode, e Structure of cobalt phthalocyanine containing optically active 1,1 -binaphthyl crown ethers units (CoPc3) (reproduced with permission from Ref. [45])... 

Scheliler M, Smykalla L, Baumarm D, Schlegel R, Hanke T, Toader M, Buchner B, Hietschold M, Hess C (2014) Structural study of monolayer cobalt phthalocyanine adsorbed on graphite. Surf Sci 608 55-60... 

Catalysts from active carbon additionally activated with cobalt- or iron- phthalocyanines are also studied [7], The results show that at current densities up to 50 mA/cm2, the polarization of the air electrodes with catalyst from active carbon promoted with FePc is lower than that of the electrode with catalyst from active carbon promoted with CoPc. At higher current density the polarization of the electrode with catalyst from active carbon promoted with CoPc is lower, which is probably connected to the lower transport hindrances, due to the more favorable structure of this catalyst. 

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