Porphyrins transition metal complexes

On the other hand, phthalocyanines and porphyrins transition metal complexes have been adsorbed on activated carbon fiber nanopouros support in the form of gas diffusion electrodes The loading of the complexes in the support involve the dissolution of the macrocycles in the proper solvent and then the addition of the (activated carbon fibers ACF). The mixtures were stirred on a magnetic stirrer for 3-4 days at room temperature and then vacuum filtered. The ACF with... 

Construction of one-dimensional multicomponent molecular arrays, transition metal complexes with terpyridines and/or porphyrins as ligands 98EJI1. 

Vasudevan P, Santosh, Mann N, Tyagi S. 1990. Transition metal complexes of porphyrins and phthalocyanines as electiocatalysts for dioxygen reduction. Transition Metal Chemistry, 15, 81-90. 

Among the main goals of electrochemical research are the design, characterization and understanding of electrocatalytic systems, (1-2) both in solution and on electrode surfaces. (3.) Of particular importance are the nature and structure of reactive intermediates involved in the electrocatalytic reactions.(A) The nature of an electrocatalytic system can be quite varied and can include activation of the electrode surface by specific pretreatments (5-9) to generate active sites, deposition or adsorption of metallic adlayers (10-111 or transition metal complexes. (12-161 In addition the electrode can act as a simple electron shuttle to an active species in solution such as a metallo-porphyrin or phthalocyanine. 

The adsorption of transition metal complexes by minerals is often followed by reactions which change the coordination environment around the metal ion. Thus in the adsorption of hexaamminechromium(III) and tris(ethylenediamine) chromium(III) by chlorite, illite and kaolinite, XPS showed that hydrolysis reactions occurred, leading to the formation of aqua complexes (67). In a similar manner, dehydration of hexaaraminecobalt(III) and chloropentaamminecobalt(III) adsorbed on montmorillonite led to the formation of cobalt(II) hydroxide and ammonium ions (68), the reaction being conveniently followed by the IR absorbance of the ammonium ions. Demetallation of complexes can also occur, as in the case of dehydration of tin tetra(4-pyridyl) porphyrin adsorbed on Na hectorite (69). The reaction, which was observed using UV-visible and luminescence spectroscopy, was reversible indicating that the Sn(IV) cation and porphyrin anion remained close to one another after destruction of the complex. 

Template and capping reactions feature in recent work. A number of sterically hindered H20 and N4 ligands have been prepared in which a quadridentate Schiff base is capped by condensation of salicylaldehyde or pyrrole-2-carbaldehyde with a series of bis(8-aminonaphthyl)alkyl ethers. These ligands combine the versatility of the Schiff base with the protective features well known for certain model porphyrin systems, and appear to be of some interest. The zinc(II) complex and other transition metal complexes have been prepared.340... 

Virtually all types of metal ions have been complexed with macrocyclic ligands.2-7 Complexes of transition metal ions have been studied extensively with tetraaza macrocycles (Chapter 21.2). Porphyrin and porphyrin-related complexes are of course notoriously present in biological systems and have been receiving considerable investigative attention (Chapter 22).8 Macrocyclic ligands derived from the Schiffbase and template-assisted condensation reactions of Curtis and Busch also figure prominantly with transition metal ions.6,7 The chemistry of these ions has been more recently expanded into the realm of polyaza, polynucleating and polycyclic systems.9 Transition metal complexes with thioether and phosphorus donor macrocycles are also known.2... 

Among what have been widely employed as model compounds for Chi, are porphyrins, phthalocyanines, and some photoactive transition metal complexes, which are more stable and easier to obtain than Chi. Interfacial layers of these insoluble compounds are generally prepared by means of vacuum sublimation or solvent evaporation. 

A review has appeared on the synthesis of enantiomerically enriched aziridines by the addition of nitrenes to alkenes and of carbenes to imines.45 A study of the metal-catalysed aziridination of imines by ethyl diazoacetate found that mam group complexes, early and late transition metal complexes, and rare-earth metal complexes can catalyse the reaction.46 The proposed mechanism did not involve carbene intermediates, the role of the metal being as a Lewis acid to complex the imine lone pah. Ruthenium porphyrins were found to be efficient catalysts for the cyclopropana-tion of styrenes 47 High diastereoselectivities in favour of the //-product were seen but the use of chiral porphyrins gave only low ees. 

In the last decade, transition metal complexes (e.g. metalloporphyrins) have been used to catalyze epoxidation. These entities can reproduce and mimic all reactions catalyzed by heme-enzymes (cytochromes P-450)54. Synthetic metalloporphyrins are analogous to the prosthetic group of heme-containing enzymes which selectively catalyze various oxidation reactions. The metallo complexes of Fe, Co, Cr, Mn, Al, Zn, Ru, etc. possessing porphyrin ligands have been mostly studied55 -57. Porphyrin ligands (4) are planar and can possess several redox states of the central metallic ions and hence they can exist as oxo metals. 

Abstract Pressure-sensitive paint (PSP) is applied to the areodynamics measurement. PSP is optical sensor based on the luminescence of dye probe molecules quenching by oxygen gas. Many PSPs are composed of probe dye molecules, such as polycyclic aromatic hydrocarbons (pyrene, pyrene derivative etc.), transition metal complexes (ruthenium(II), osumium(II), iridium(III) etc.), and metalloporphyrins (platinum (II), palladium(II), etc.) immobilized in oxygen permeable polymer (silicone, polystyrene, fluorinated polymer, cellulose derivative, etc.) film. Dye probe molecules adsorbed layer based PSPs such as pyrene derivative and porphyrins directly adsorbed onto anodic oxidised aluminium plat substrate also developed. In this section the properties of various oxygen permeable polymer for matrix and various dye probes for PSP are described. 

Keywords TDDFT Excitation energies Excited states Transition metal complexes Electronic spectra Metallotetrapyrroles Metallocarbonyls a-diimine complexes Porphyrins Porphyrazines Phthalocyanines Werner complexes Sandwich complexes... 

Fig. 15.17. Current in milliamperes cm-2 for CO production from C02 using C02+ tetraphenyl porphyrins modified with various pyridyl derivatives. (Reprinted with permission from T. Atoguchi, A. Aramata, and M. Engo, C02 Reduction by Macrocyclic Transition Metal Complex-Modified Electrodes," in Proc. International Symposium on Chemical Fixation of Carbon Dioxide, p. 338, Fig. 5,1991.)...

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