Transition metallophthalocyanines

Metallophthalocyanines, (MPc s) possess a very intense absorption at about 680 nm (e> 10s dm3 m jl"1 cm 1) which is blue shifted on complexation with third row transition elements. They can absorb a large fraction of the solar spectrum, but their potential application to hydrogen production is limited by their tendency to aggregate in solution118 (although where the system allows, this aggregation can be prevented by the use of pyridine (5% w/w) or micelles). 

HDN with Metallophthalocyanines. The above considerations clearly show that the catalytic site geometry is important in HDN. It is difficult to control, or even to identify, the catalyst site in conventional catalysts such as the commercial Co-Mo-alumina catalyst. On the other hand, homogeneous catalysts with transition metal complexes provide a well-defined catalytic site. Unfortunately, most homogeneous catalysts are not sufficiently stable to be used at the temperatures required for the hydrogenation of hetero compounds. A class of catalysts that are thermally stable are the metallophthalocyanines,... 

Subphthalocyanines contain a delocalized 14 -electron conjugated pathway, and are brightly colored compounds, both in the solid state and in organic solution. As such, they exhibit fairly strong absorption bands in their visible electronic spectrum. For instance, subphthalocyanine 2.284 exhibits a Soret-like absorbance band at ca. 305 nm and a more intense Q-like transition at 565 nm (e = 50 100 M cm and 89 100 M cm , respectively, in CHCI3). These bands are blue-shifted relative to those of the metallophthalocyanines (by c. 20-30 nm and 120-130 nm in the Soret and Q-band regions, respectively), and exhibit absorption coefficients that typically are smaller than those of the metallophthalocyanines. ... 

The synthesis of metallophthalocyanines [118] from phthalic anhydride and urea is another interesting example of a mechanism with charge development in the transition state (Eq. 34) and in which a large specific microwave effect was apparent. 

Metallophthalocyanines, MPc, are known for their high thermal stability and very low solubility in any solvents. Transition metal-based phthalocyanines have attracted attention in the areas of fuel cells, gas sensors and biosensors . Most of these applications require the use of phthalocyanines in the form of thin films. Further, it is desirable to have ordered, well-packed, and oriented molecular layers of phthalocyanines on various substrates. The metal phthalocyanines constitute an important class of compounds that provide models for theoretical and experimental studies involving electron-mediated processes one of the main areas of interest is the electrocatalytic reduction of oxygen by metal phthalocyanines. ... 

The metal ion in metallophthalocyanines lies either at the center of a single phthalocyanine ligand (Pc = dianion of phthalocyanine) (Fig. 3), or between two rings in a sandwich-type complex (40). Phthalocyanine complexes of transition metals usually contain only a single Pc ring while lanthanide-containing species usually form bis(phthalocyanines), where the r-systems interact strongly with each other. 

When R4PCM compounds with R = OCsHu, 0C8H 7, OC10H21 and M = Ni, Pd, Pt are compared, the melting points of these compounds show that the metallophthalocyanines containing pentyloxy substituents do not exhibit liquid crystalline behavior [78,79]. Those with octyloxy chains show a transition temperature between 100 and 84°C (M = Ni, 100°C M = Pd, 92°C M = Pt, 84°C). The melting points of the decyloxy series are between 86 and 64°C (M = Ni, 86°C M = Pd, 74°C M = Pt, 64°C). As can be seen from these data, the longer the chain the lower the transition temperature. 

Tetrapyrrolic macrocycles, such as porphyrin, consisted of four pyrrole units bonded by different bridges, for example methene in the case of porphyrins and aza-methene in the case of phthalocyanines [1]. These ligands can complex metal ion transition and the synthesized metallocomplexes are extremely stable [2, 3]. While some metalloporphyrins constitute the redox center of naturally occurring proteins, like heme in hemoglobin, metallophthalocyanines are purely synthetic molecules. The (electro) chemical properties of MN4 complexes have been widely studied and have been particularly used for the catalysis of several electrochemical reactions in homogeneous solutions [4]. It was shown that the electrochemical properties of a... 

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