Ruthenium metalloporphyrins

In 1988, Schiffrin s group [4] claimed that the use of lutetium biphthalocyanine (LuPc2) complex more hydrophobic than Fc enabled observation and investigation of a true , or heterogeneous, ET across the 0/W interface. A series of subsequent papers reported ET systems by other hydrophobic metal complexes including tin diphthalo-cyanine [5], iron and ruthenium metalloporphyrin complexes with pyridine [6] and Fc derivatives [7]. These experimental studies then stimulated theoretical studies on the ET kinetics [8-12]. 

Therefore, the classical rrani-dioxoRu(VI) - oxoRu(IV) catalytic cycle [2] (Fig. 1) can be ruled out as the primary reaction pathway in case of rapid catalytic oxygenation. The apparent zero-order kinetics observed are consistent with a steady-state catalytic regime accessible from different initial states of ruthenium metalloporphyrin. Indeed, common oxidants, other than aromatic iV-oxides, such as iodosylbenzene, magnesium monoperoxyphthalate, Oxone and tetrabutylammonium periodate produced the trans-dioxoRu(VI) species from Ru (TPFPP)(CO) under reaction conditions but were ineffective for the rapid catalysis. 

While metalloporphyrin carbene complexes are well established for ruthenium and osmium, they are less well known for rhodium. Cationic rhodium porphyrin carbene intermediates were implicated in a report by Callot et al. in w- hich... 

Metalloporphyrins have proved their efficiency as ruthenium carbonyl hg-ands for the enantioselective cyclopropanation of styrene [50,51]. 

To select the metal to be incorporated into the substrate porphyrin unit, the following basic properties of metalloporphyrins should be considered. The stability constant of MgPor is too small to achieve the usual oligomeric reactions and purification by silica gel chromatography. The starting material (Ru3(CO)i2) for Ru (CO)Por is expensive and the yield of the corresponding metalation reaction is low. Furthermore, the removal of rutheniirm is difficult, and it is likewise difficult to remove the template from the obtained ruthenium CPOs. Therefore, ZnPor is frequently used as a substrate in this template reaction, because of the low prices of zinc sources (zinc acetate and/or zinc chloride), the high yield in the metalation reaction, the sufficient chemical stability of the ZnPor under con-... 

In the second oxidation method, a metalloporphyrin was used to catalyze the carotenoid oxidation by molecular oxygen. Our focus was on the experimental modeling of the eccentric cleavage of carotenoids. We used ruthenium porphyrins as models of cytochrome P450 enzymes for the oxidation studies on lycopene and P-carotene. Ruthenium tetraphenylporphyrin catalyzed lycopene oxidation by molecular oxygen, producing (Z)-isomers, epoxides, apo-lycopenals, and apo-lycopenones. 

Of considerable interest was the demonstration that metalloporphyrins and the like can be used as nonmetallic catalysts in electrochemical reactions, nourishing hopes that in the future, expensive platinum catalysts could be replaced. Starting in 1968, dimensionally stable electrodes with a catalyst prepared from the mixed oxides of titanium and ruthenium found widespread use in the chlorine industry. 

The chemically catalyzed oxidation of carotenoids by metalloporphyrins has also been described in the literature. In 2000, French et al. described a central cleavage mimic system (ruthenium porphyrin linked to cyclodextrins) that exhibited a 15,1 S -regiosclectivity of about 40% in the oxidative cleavage of [3-carotene by tert-butyl hydroperoxide in a biphasic system (French et al. 2000). 

These reports sparked off an extensive study of metalloporphyrin-catalyzed asymmetric epoxidation, and various optically active porphyrin ligands have been synthesized. Although porphyrin ligands can make complexes with many metal ions, mainly iron, manganese, and ruthenium complexes have been examined as the epoxidation catalysts. These chiral metallopor-phyrins are classified into four groups, on the basis of the shape and the location of the chiral auxiliary. Class 1 are C2-symmetric metalloporphyrins bearing the chiral auxiliary at the... 

Oxidizing enzymes use molecular oxygen as the oxidant, but epoxidation with synthetic metalloporphyrins needs a chemical oxidant, except for one example Groves and Quinn have reported that dioxo-ruthenium porphyrin (19) catalyzes epoxidation using molecular oxygen.69 An asymmetric version of this aerobic epoxidation has been achieved by using complex (7) as the catalyst, albeit with moderate enantioselectivity (Scheme 9).53... 

Metal ions within organometallic dendrimers can be incorporated at the core, in the branches, or at branch points. Examples of dendrimers having metal-ion-containing cores included the dendritic metalloporphyrins [66,67] and related materials reported by Aida and Enomoto [68],Diederich et al. [69], Moore et al. [70], and Erechet et al. [71], dendritic terpyridine-ruthenium complexes report-... 

Alkyl and aryl systems - As already mentioned in Sect. 3.2, dialkyl ruthenium and osmium porphyrins have been synthesized according to Eq. (22) by the reaction of metalloporphyrin dianions [M(P)]2 with alkyl iodides [223, 260, 261,307]. These dianions have been obtained by reduction of porphyrin dimers [M(P)]2. 

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. 

Figure 5.61 Schematic representation of a [Ru(bpy)3]2+/a-ZrP viologen structure on silica, plus the sequence of fast (1,2) and slow (3) electron transfer steps that follow photoexcitation of the photoactive ruthenium-containing polymer MDESA, p-methoxyaniline diethylsulfonate. Reprinted from Coord. Chem. Rev., 185-186, D. M. Kaschak, S. A. Johnson, C. C. Waraksa, J. Pogue and T. E. Mallouk, Artificial photosynthesis in lamellar assemblies of metal poly(pyridyl) complexes and metalloporphyrins, 403-416, Copyright (1999), with permission from Elsevier Science...

There are several photocatalysts mimicking hydrogenase activity that are not based on metalloporphyrin systems. Among them there are mixed-valence complexes of rhodium or iridium, [41] as well as complex systems encompassing photosensitizers (eg ruthenium complexes) attached to a catalytic bimetallic centre [43], The design of more sophisticated systems approaches that of photosynthetic processes [44],... 

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