Metalloporphyrin, water-soluble

Oxo-hydroxo tautomerism as a useful tool in oxygenation reactions catalyzed by water-soluble metalloporphyrins 98CC2167. 

An interesting, pH-dependent mechanistic changeover was reported in the H2A-02-[Fem(TPPS)] (TPPS = 5,10,15,20-tetrakis(p-sulfonatophe-nyl)porphyrinate) system in aqueous solution (23). This water-soluble metalloporphyrin exists as a monomer under slightly acidic conditions and reacts with ascorbic acid on the time-scale of several hours to produce [Fen(TPPS)] in the absence of dioxygen. The formation of the [Fem(TPPS +)] radical was also reported at pH 5, but it is not clear how... 

Scheme I. Structures of sulfonated robust metalloporphyrin complexes. The axial ligand of these water-soluble metalloporphyrins depend on the pH value, at acidic pH an hydroxo ligand occupies the axial position whereas it is a water molecule at basic pH values.

Porphyrin-based self-assembled molecular squares 389 can form mesoporous thin films in which the edge of a square, thus the size of the cavity, can be adjusted by appropriate choice of substituents [8]. Fibers that form coil-coiled aggregates with distinct, tunable helicity are built from crown ethers bearing porphyrins 390 [9]. In addition to the porphyrin applications discussed in Sections 6.3.2.2 and 6.4, dendrimer metalloporphyrins 391 to be applied in catalysis [10] and the water-soluble dendritic iron porphyrin 319 modelling globular heme proteins [11] can be mentioned. 

The second and third steps involve successive additions of the pyrazine and non-surfactant water soluble metalloporphyrin complexes to the template submerged in the aqueous phase (Steps 2 and 3, respectively). The two-layered assembly is then removed from the water through a protective monolayer of stearic acid to prevent disruption of the film structure (Step 4). If instead of removing the assembly in Step 4, Steps 2 and 3 were successively repeated, multi-layered assemblies having the essential features described in Figure 1 might be realized. 

Figure 2. Representation of the dye assembly construction procedure (O-) stearic acid (-0-) surfactant metalloporphyrin (MTOAPP) and (-0-) water soluble porphyrin...

The syntheses, and especially the purification, of water-soluble porphyrin complexes are often different from the above-mentioned methods, and experimentally more difficult, because of the salt-like character of the compounds. Thus, besides the reaction conditions, some notes on the workup are given. Some papers do not specify the counter ions neutralizing the charge of the respective metalloporphyrin. In such cases, just the respective ion of the porphyrin complex is noted. The porphyrin systems involved are specified in Table 1. 

It has been shown that Gram-positive bacteria, such as Escherichia coli, are susceptible to the photosensitizing action of a variety of photosensitizers, among them amphiphilic metalloporphyrins (Pd11) [16], cationic metallophthalocyanines (Zn11) [15,17], or water-soluble derivatives of chlorophylls [18]. 

As part of the work on model heme FeNO complexes, mechanistic studies on the reversible binding of nitric oxide to metmyoglobin and water soluble Fe, Co and Fe porphyrin complexes in aqueous solution, ligand-promoted rapid NO or NO2 dissociation from Fe porphyrins, reductive nitrosylation of water-soluble iron porphyrins, activation of nitrite ions to carry out O-atom transfer by Fe porphyrins, demonstration of the role of scission of the proximal histidine-iron bond in the activation of soluble guanylyl cyclase through metalloporphyrin substitution studies, reactions of peroxynitrite with iron porphyrins, and the first observation of photoinduced nitrosyl linkage isomers of FeNO heme complexes have been reported. 

Polymers can be used to locate reagents at particular sites and to provide unique surface environments. The possible applications of functionalized polymers in solar energy storage systems have been reviewed in detail. Metalloporphyrins or bipyjRu " " can be attached to various water-soluble polymers via covalent or electrostatic linkages. The ability of the dye to photoreduce dissolved in the aqueous phase, depends strongly upon... 

Radiative and Nonradiative Decay Processes - Due to the potential application of these compounds as photosensitizers for photodynamic therapy" the photophysical properties of porphyrins and phthalocyanines, and their corresponding metal complexes, have been investigated extensively over the past decade. The photophysical properties of water-soluble metalloporphyrins, and especially the tetraphenylsulfonates," have been re-examined but nothing new has been found. The disulfonated metallophthalocyanines (MPcS2, where M = Al ", Ga" , or Zn") form complexes with fluoride ions for which the fluorescence yields and lifetimes are decreased with respect to the parent dyes while there are... 

J. Bernadou, A. Fabiano, A. Robert, B. Meunier, Redox tautomerism in high-valent metal-oxo-aquo complexes.Origin of the oxygen atom in epoxidation reactions catalyzed by water-soluble metalloporphyrins,/. Am. Chem. Soc. 116 (1994) 9375. 

Hydrated electrons react with certain water-soluble metalloporphyrin complexes, reducing the porphyrin ligands to pi-radical species. When the metal centers are Zn(II), Pd(II), Ag(II), Cd(II), Cu(II), Sn(IV), and Pb(II), the radical complexes are produced at diffusion-controlled rates and decay with second-order kinetics.188 Fe(III) porphyrins, on the other hand, yield Fe(II) porphyrins.189 Rather different behavior is seen in the reaction of e (aq) with [Ru(bpy)3]3 + here, parallel paths generate the well-known luminescent excited-state [ Ru(bpy)3]2 + and another reduced intermediate, both of which decay to the ground-state [Ru(bpy)3]2+, 190 In a direct demonstration of the chemical mechanism of inner-sphere electron transfer, [Coni(NH3)5L]2+ complexes where L = nitrobenzoate and dinitrobenzoate react with e (aq) to form Co(III)-ligand radical intermediates, which then undergo intramolecular electron transfer to yield Co(II) and L.191... 

In 10-2 M HC1, [In(tmpyp)]5+ has bands at 424 nm (e = 390,000), 518 nm (e = 3690), 558 nm (c = 23,200), and 597 nm (e = 4660). The spectrum is similar to that of indium(III)-tetraphenylporphyrin.16 The [In(tmpyp)]5+ is fully water soluble, and rapid acid solvolysis occurs only above 3 M HC1 levels. Refluxing a divalent metal chloride with H2tmpyp in water, and keeping the pH between 3 and 5, is the general method used to prepare the Cu2+, Zn2+, Ni2+, Mn3+, Fe3+, and Co3+ compounds.6 The 642-nm free-base porphyrin band disappears when the incorporation reaction is complete. The high-pH conditions (a) reduce the concentration of unreactive centrally protonated15 porphyrins, (b) minimize the extent of acid catalyzed metalloporphyrin solvolysis reactions,17 and (c) increase the concentration of the often more reactive hydrolyzed metal ion forms.18... 

Balahura, R.J., A. Sorokin, J. Bernadou, and B. Meunier (1997). Origin of the oxygen atom in C-H bond oxidations catalyzed by a water-soluble metalloporphyrin. Inorg. Chem. 36, 3488-3492. 

SWCNTs were modified with several water-soluble pyrene derivatives (1-pyreneacetic acid, 1-pyrenecarboxylic acid, 1-pyrenebutyric acid, and 8-hydroxy-l,3,6-pyrenetrisulfonic acid) bearing negatively charged ionic head-groups, to act as anchors to several pyridium headgroups present in a series of water-soluble metalloporphyrins [MP] + (M = Zn, Co, and Fe) [60a]. Interactions between the metalloporphyrins and SWCNTs proceeded through a combination of associative van der Waals (spacer-CNT) and electrostatic interactions (metalloporphyrins-spacer-CNT), as demonstrated by the combination of spectroscopic and surface techniques. 

Extending the studies on the reductive electron transfer from reduced metalloporphyrin states to [60]fullerene into aqueous media requires employment of a water-soluble form of [60]fullerene. Therefore, a micellar assembly consisting of the fullerene incorporated into Triton X-100 was investigated. The electron transfer does indeed occur across the interface of the micellar assembly. The rates exhibit a considerable slow-down compared to the homogeneous systems but, on the other hand, show a clear dependence on the reduction potential of the water-soluble metalloporphyrin. 

The azide and dichloride radicals react more rapidly and the organic radicals shown above react more slowly. Many water-soluble metalloporphyrins were oxidized by these reactions, and radical cations were generated from Zn", Cd", Cu", Pd" and Sn -porphyrins. Other metalloporphyrins were subsequently studied. 

P. Peretz, D. Solomon, D. Weintraub, and M. Faraggi, Chemical Properties of Water-Soluble Porphyrins. 3. The Reaction of Superoxide Radicals with Some Metalloporphyrins, Int. J. Radiat. Biol., 42 (1982) 449. 

This survey is limited to model systems based on synthetic water-soluble metalloporphyrins. The activity of KHSOs/sulfonated metalloporphyrin models has been checked with the usual... 

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