Dendrimers metal porphyrin

Diederich et al. had postulated that the highly reactive iron-oxo species, arising from oxygen transfer from the oxidant to the Fem site [87], should be greatly stabilised by enclosure within a dendritic superstructure. The catalytic potential of the dendrimers 6 a-c was determined in the epoxidation of alkenes [83 a, 88] (1-octene and cyclooctene) and the oxidation of sulphides [83 a] ((methylsulphanyl)benzene and diphenyl sulphide) to sulphoxides - in dichloro-methane with iodosylbenzene as oxidising agent. Compared to the known metal-porphyrin catalysts, 6a-c exhibit only low TON (7 and 28, respectively, for... 

Star-shaped multi-porphyrin arrays have been constructed to mimic energy funneUng in photosynthesis. These dendrimers contain free-base porphyrin cores (Pfb) connected to four dendrons consisting of 1,3, or 7 zinc-metallated porphyrins (Pzn) embedded in an organic matrix coimected by ether linkages (Scheme 21) [70,71]. The periphery consists of methoxy-terminated poly(aryl ether) dendrons. For comparison, cone-shaped arrays consisting of Pfb cores monosubstituted with Pz dendrons were also synthesized. 

FIGURE 5.13 Poly(propylene imine) dendrimers with peripheral Zn-metallated porphyrins. 

Carboxylic acid terminated poly(aryl ether) dendrimers acted as good-microreactors for the photooxidation of ( )-stilbene and E,E)-1,4-diphenyl-1,3-butadiene sensitized by 9,10-dicyanoanthracene. The photooxidation of ( )-stilbene led to benzaldehyde, while ( , )-1,4-diphenyl-1,3-butadiene afforded the peroxide (190) in quantitative yield. In photodynamic tumor therapy, the oxidation by metalloporphyrines as visible-light-sensitizers is very important. Some non-metallated porphyrine and tetraphenylchlorins have been reported to act as visible-light-sensitizers for the oxidation of alkenes. ... 

Dendrimer chemistry has taught us that these molecules create a nano-sized closed space that, presumably, is the origin of the specific physical properties of this class of materials. As the next stage of dendrimer chemistry, a macromolecule capable of creating such a space inside its molecule is proposed. To create the nano-sized space, porphyrin is considered to be the best candidate for the component molecules, because it has versatile properties associated with its expanded 7i-electron system and the incorporated metal. The resultant multi-detectable properties of porphyrin, that is, a number of its properties are detectable by many physical methods, may reveal the function of the nanometer-sized space. 

Dendrimers with a Porphyrin Metal Complex as a Core.212... 

Dendrimers built around a metal complex as a core. These compounds can be considered metal complexes of ligands carrying dendritic substituents (Fig. 1 a). The most commonly used metal complex cores are porphyrin complexes, polypyridine complexes, and ferrocene-type compounds. 

Figure 16.17 Amine-terminated polypropylene imine) dendrimers act as tridentate ligands for the complexation of transition metals [217] (a), and can function as templates for the assembly of Troger s base dizinc(ll) bis-porphyrin molecules, (b) [218]...

The aim of this chapter is limited to reviewing some recent developments concerning luminescent dendrimers that can play the role of ligands and sensors for luminescent and nonluminescent metal ions, mainly investigated in our laboratories, with particular references to transition metal or lanthanide ions. We will not discuss dendrimers constituted by polypyridine metal complexes [21] and porphyrins [22] since it is outside the scope of the present paper. 

The design of dendritic multiporphyrin systems [18] permits energy transfer over longer distances. The outer shell of the dendrimer shown in Fig. 5.14 is made up of eight porphyrin-zinc complexes as energy donor units. Excitation of the units of the outer shell leads to fluorescence emission of the metal-free porphyrin core as a result of energy transfer from the periphery to the energy acceptor [19]. 

Porphyrin dendrimers are suitable as sensors for small molecular and ionic analytes. Unsubstituted metal-free porphyrins often show poor solubility in water. However, if it proves possible to envelop them in hydrophilic dendrimers they can be used in water as fluorescent pH indicators because they exhibit distinct changes of their absorption and emission bands owing to protonation of... 

The electroactive unit is the core of the dendrimer (Figure 2a). The most commonly used units in this category are metal-polypyridine complexes and porphyrins. 

Figure 5. Structures of some functional dendrimers A. Dendrimer with lanthanide ion as the central core with dendrons as ligands B. Dendrimer based on metal complex C. Silicon-based ferrocenyl dendrimer and D. Dendrimer with zinc-porphyrin core...

Generally speaking, an antenna for light harvesting is an organized multicomponent system in which several chro-mophoric molecular species absorb the incident light and channel the excitation energy to a common acceptor component. Artificial antenna systems based on porphyrin arrays [63], multichromophoric cyclodextrins [64], polynuclear metal complexes [65, 66], dendrimers [66-68], and polymers [69, 70] have been reported. In all these systems, the chromophoric units are connected by means of covalent... 

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