Porphyrin entrapment

The principle is to activate molecular oxygen, by the Mn porphyrin entrapped in the conductive polymer (polypyrrole), and thus to form oxo species at the electrode surface. Then, these oxo complexes can oxidize the hydrocarbons or phenol. The catalyst should be regenerated and this can be done by electroreduction at a constant potential (typically at — 0.5 V/SCE in acetonitrile). Moreover, the solution should contain an axial base (i.e. imidazole), and an activator (benzoic anhydride) [165,172]. 

Fujiwara ST, Gushikem Y, Pessoa CA, Nakagaki S (2005) Electrochemical studies of a new iron porphyrin entrapped in a propylpyridiniumsilsesquioxane polymer immobilized on a S102/A1203 surface. Electroanalysis 17 783-788... 

Figure 5.11 Entrapped in a silica aerogel, this manganese porphyrin is nine times more active than in solution. (Reproduced from ref. 22, with permission.)...

The flexible ligand method, consisting of the tetramerization of pyrrole and an aldehyde, can be used for the entrapment of metallo-porphyrins (MePOR) in situ in the supercages of faujasite-type zeolites (Scheme 10.7).[74]... 

Metal phthalocyanines are easily synthesized by vapor-phase condensation of four molecules of dicyanobenzene in the presence of molecular sieves such as faujasites or A1PO-5 (123-126). This results in direct entrapment of the macrocycle inside the molecular sieve s channels and cages. There are also reports of ship-in-a-bottle synthesis of porphyrins in zeolites, but since porphyrin synthesis requires a mixture of pyrrole and an aldehyde instead of a single compound, porphyrin synthesis is a much less clean process than phthalocyanine preparation (127). Alternatively, soluble porphyrins or phthalocyanines can be added to the synthesis gel of, for example, zeolite X. This also results in entrapped complexes (128). 

Cationic amphiphilic CDs, heptakis[2-co-amino-0-oligo(ethylene oxide] hexyl-thio-ji-CD nanoparticles, have encapsulated anionic porphyrins (TPPS) by entangling these molecules within the aliphatic chains aligning both faces of the cationic amphiphilic CD. These nanoparticles were demonstrated to preserve the photodynamic properties of the entrapped photoactive agent. The photodynamic efficacy of the carrier/sensitizer nanoparticles was proven by in vitro studies on tumor HeLa cells showing significant cell death upon illumination with visible light [88]. 

Zhang GD, Harada A, Nishiyama N, Jiang DL, Koyama H, Aida T, Kataoka K (2003a) Polyiori complex micelles entrapping cadonic dendrimer porphyrin Effecdve photosensidzer for photodynamic dierapy of cancer. J Control Release 93 141—150. 

Light-induced charge separation was treated in the porphyrin section 4.4, activities of entrapped dyes in section 4.5. In the following, we discuss the effect of vesicle viscosity on photoreactions and photochemical labelling. 

Figure 7.27 Even inorganic salts, such as cadmium nitrate, can be entrapped in crystals of meso-tetrasubstitutedporphyrins. Here one cadmium ion binds two pyridine rings from meso-tetrapyridinium porphyrin, two nitrate counterions and two water molecules (all symbolized by a blue spot)...

Tetrabrucine-appended porphyrin was proved to be an excellent gelator of CD3OD it entraps about 3000 molecules of solvent per one gelator molecule. Figure 8.11 shows its VCD and IR absorption spectra in the C=O region for the... 

The existence of fluid inclusions in quartz (Reese 1898) and, especially, entrapment of organic matter in such fluid inclusions in mineral phases in the form of porphyrins and other fluorescing organic matter, is known and documented since Haberland (1939) and Neumann Rosenquist (1940). 

Figure 2.5.10 Typical dissolution pattern in the different regions of vesicle membranes the entrapped water volume 9 may contain an ionic dye, which can be separated from dyes in the bulk water phase by gel chromatography. The headgroups 3 and 7 may consist of redox systems, e.g., quinones in different oxidation states. The aqueous and membraneous surface regions 2,8 and 4,6 may enrich polar or charged compounds. Large and flat hydrophobic molecules (e.g., porphyrins) prefer the same regions. The central region 5 is thought take up some hydrophobic steroids and carotenoids.

Another promising example of a metal-based sensor can be seen in the work of Lee and Okura (239) who used entrapped platinum octaethylporphyrin complexes to form photostable devices. In their study, they found by adding the surfactant Triton X-100 to the sol-gel mixture, they could improve homogeneity and phosphorescence of the dye-containing glass. Encapsulated porphyrin molecules have also been used successfully in the sensing of nitrogen dioxide (240) and, as will be discussed below, can be used to sense metal ions. 

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