Porphyrins polymeric

With the knowledge that aniline, pyrrole and phenol groups may be involved in the formation of electroactive 

Film thickness and the charge-transfer process are crucial factors in the design of porphyrinic-film amperometric sensors. Both of these processes influence the range of 

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In the present case, the electron hopping chemistry in the polymeric porphyrins is an especially rich topic because we can manipulate the axial coordination of the porphyrin, to learn how electron self exchange rates respond to axial coordination, and because we can compare the self exchange rates of the different redox couples of a given metallotetraphenylporphyrin polymer. To measure these chemical effects, and avoid potentially competing kinetic phenomena associated with mobilities of the electroneutrality-required counterions in the polymers, we chose a steady state measurement technique based on the sandwich electrode microstructure (19). 

Thirdly, one experiment to measure D was carried out with the sandwich of electrodes and polymeric porphyrin film exposed to a gas phase rather than a fluid liquid bathing environment. This... 

Dloxygen reduction electrocatalysis by metal macrocycles adsorbed on or bound to electrodes has been an Important area of Investigation (23 ) and has achieved a substantial molecular sophistication in terms of structured design of the macrocyclic catalysts (2A). Since there have been few other electrochemical studies of polymeric porphyrin films, we elected to inspect the dloxygen electrocatalytic efficacy of films of electropolymerized cobalt tetraphenylporphyrins. All the films exhibited some activity, to differing extents, with films of the cobalt tetra(o-aminophenylporphyrin) being the most active (2-4). Curiously, this compound, both as a monomer In solution and as an electropolymerized film, also exhibited two electrochemical waves... 

A similar catalytic activity with a monomeric porphyrin of iridium has been observed when adsorbed on a graphite electrode.381-383 It is believed that the active catalyst on the surface is a dimeric species formed by electrochemical oxidation at the beginning of the cathodic scan, since cofacial bisporphyrins of iridium are known to be efficient electrocatalysts for the tetraelectronic reduction of 02. In addition, some polymeric porphyrin coatings on electrode surfaces have been also reported to be active electroactive catalysts for H20 production, especially with adequately thick films or with a polypyrrole matrix.384-387... 

The use of porphyrinic ligands in polymeric systems allows their unique physio-chemical features to be integrated into two (2D)- or three-dimensional (3D) structures. As such, porphyrin or pc macrocycles have been extensively used to prepare polymers, usually via a radical polymerization reaction (85,86) and more recently via iterative Diels-Alder reactions (87-89). The resulting polymers have interesting materials and biological applications. For example, certain pc-based polymers have higher intrinsic conductivities and better catalytic activity than their parent monomers (90-92). The first example of a /jz-based polymer was reported in 1999 by Montalban et al. (36). These polymers were prepared by a ROMP of a norbor-nadiene substituted pz (Scheme 7, 34). This pz was the first example of polymerization of a porphyrinic macrocycle by a ROMP reaction, and it represents a new general route for the synthesis of polymeric porphyrinic-type macrocycles. 

Other examples involve the immobilization of ruthenium porphyrin catalysts [74]. While Severin et al. generated insoluble polymer-embedded catalysts 16 by co-polymerizing porphyrin derivatives with ethylene glycol dimethacrylate (EGD-MA) [74 a], Che et al. linked the ruthenium-porphyrin unit to soluble polyethylene glycol (PEG) 17 [74b]. Both immobilized catalysts were employed in a variety of olefin epoxidations with 2,6-dichloropyridine N-oxide (Gl2pyNO), providing similar conversions of up to 99% and high selectivities (Scheme 4.9). 

Heating PcSi(OH)2, Ge(OH)2Pc, Ge(OH)2HP with ethylenglycol in a molar ratio of 1 1 in hi boiling solvents, polyoxyethylenoxy chelates (76) where synthesized. In order to t analogous polymeric porphyrin comjdexes, bifunctional Ge(0CH2CH20H)2Tpp, EtioP (71) ere heated under vacuum 3qj... 

Only few informations are available on polymeric porphyrins in contrast to expected interesting properties such as visible light energy conversion, catalytic activity due to... 

Ni(II)-meso-tetramethylporphine ( 3a) was converted by two ways into polymeric porphyrins Firstly, bromation of 83a) in CCI4 in the presence of AIBN gave the expected monobrommethylporphyrin 83 b). This reactive intermediate (detected as methoxymethyiderivate 83 c) is reacting easily with a /8-pyrrol position of another porphyrin (Eq. 38). Beside dimer and trimer formation the polymer 84) was obtained (yield 21%). 83 c) is also converted into 84) with HCl (51% yield). In the electronic spectra the broader Soret band at 425 nm of 84) is shifted to the bathochrome side due to connection in /8-position of the pyrrole ring compared with starting compound 83 a). 

Polymeric N4-Chelates Through the Ligand 5.1 Polymeric Porphyrins... 

The use of metalloporphyrins which show metal-metal interactions can be an effective strategy for the synthesis of metal chain complexes. Some of these complexes exhibit high or unusual electric conductivities . Although much synthetic work has been devoted to metalloporphyrin chemistry ", only a few examples of porphyrin compounds containing metal-metal interactions have been published. Apart from the conducting polymeric porphyrins described by Ibers and Hoffman , two classes of metal-metal... 

Fig. 25 a Schematic representation of the polymeric porphyrin strings b linear manganese porphyrin-polymer 30 connected through a tri-nickel-complex [76] c optically active polymer 31 formed from chiral di-porphyrins [77]... 

Similar measurements using either walljet electrochemistry or steady-state microelectrode voltammetry have been reported for layer-by-layer assembled and interfadally polymerized materials, respectively [24,28]. Additional measmements were made spectrophotometrically with polymerized porphyrin squares by using a U-tube. Results summarized in Fig. 5 revealed the following (a) After normalizing for differences in film thickness, transport through polymeric membranes is two to three orders of magnitude faster... 

Structurally uniform polymeric porphyrins are expected if terephthalaldehyde is reacted with pyrrole in boiling propionic acid. Polymers from this reaction have been described [53], The authors cleaned the product from polypyrrole and low molecular weight porphyrins by washing with methanol and chloroform, and introduced different metal ions by treatment with metal salts in an ethanol/water mixture. But the polymers which exhibited specific conductivities of 10 S cm (up to 10 S cm by doping with I2) were analyzed only by IR-spectra. 

The interfacial polycondensation technique, in which reactive comonomers are dissolved in separate immiscible solutions and are thereby constrained to react only at the interface between two solutions, has been used to synthesize chemically asymmetrical polymeric porphyrin (M = Zn, Cu, Ni, Pd or 2H) films [122-124]. Tetrakis(4-aminophenyl)-, tetrakis(4-hydroxyphenyl)porphyrins (29, R = -NH2, -OH) or aliphatic amines in one solvent were reacted with tetrakis(4-chlorocarboxyphenyl)porphyrins (29 (R= -CO-Cl) or aliphatic diacylchlorides, respectively, in the other solvent (see Experiment 6-4, Section 6.6). Figure 6-4 shows schematically the formation of asymmetric polyamide porphyrin films. The dependence of the film growth on monomer concentration and time has been studied in detail. Typical film thicknesses are in the range of 0.1-10 pm. The unique chemical asymmetry is shown by distinctive differences in the concentration and type of functional groups present. The photoactivities of the polymeric porphyrin films were measured in dry sandwich cells. 

Experiment 6-4 Interfacial Polycondensation to Polymeric Porphyrins (Section 6.2.2, Fig. 6-4) [123]... 

With fully water-soluble porphyrins, the metal-incorporation rate has been found to be first order in free base, metal, and anion. However, it has been suggested that during incorporation of metals in poorly soluble porphyrins, which would correspond to the situation of polymeric porphyrins, intermediate ( sitting-atop complexes) can be formed. Incorporation kinetics were suggested to be second order in metal and first order in porphyrin. The number of monolayers of polymeric porphyrins occupied by Ni(II) increases with its initial concentration. At trace concentration levels, film thickness is not important because only the first few layers are occupied, and the analyte signal does not depend on film thickness. The concentration levels (10 -10 M) and preconcentration times (40-100 seconds) are not sufficient to exceed the film capacity of monolayer film to incorporate Ni(II). However, for high Ni(II) concentra-... 

Figure 7. Differential pulse voltammograms obtained for oxidation of 5 iM NO on a carbon fiber electrode (a) and carbon fiber electrode covered with polymeric porphyrin (TMHPP)Ni and Nation (b).

Figure 8. Schematic diagram of electrochemical nitric oxide sensor based on conductive polymeric porphyrin.

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