Porphyrins covalent

Macrocyclic receptors made up of two, four or six zinc porphyrins covalently connected have been used as hosts for di- and tetrapyridyl porphyrins, and the association constants are in the range 105-106 M-1, reflecting the cooperative multipoint interactions (84-86). These host-guest complexes have well-defined structures, like Lindsey s wheel and spoke architecture (70, Fig. 27a), and have been used to study energy and electron transfer between the chromophores. A similar host-guest complex (71, Fig. 27b) was reported by Slone and Hupp (87), but in this case the host was itself a supramolecular structure. Four 5,15-dipyridyl zinc porphyrins coordinated to four rhenium complexes form the walls of a macrocyclic molecular square. This host binds meso-tetrapyridyl and 5,15-dipyridyl porphyrins with association constants of 4 x 107 M-1 and 3 x 106 M-1 respectively. 

Nevertheless, the inverse region is observed in the particular case where the electron donor and the electron acceptor are held apart by a bridge (e.g. porphyrins covalently linked to quinones). 

Another mode of rigid linking of P and Q has been suggested [152]. In this work porphyrin covalently linked with cyclodextrin, PC, was reported to have... 

Photoinduced intramolecular electron tunneling was observed also in some other porphyrin containing bridge molecules, such as porphyrin covalently linked to phenolphthalein [308], dimethylaniline — mesoporphyrin II — quinone triad [309], Zn porphyrin-viologen-quinone triad [310], carotenoid — porphyrin -diquinone tetrad [311]. The influence of conformational state of porphyrin-viologen bridge molecules on the rate of PET reactions was studied in Ref. [312]. 

The vast majority of the dyad models for photosynthetic electron transfer have consisted of synthetic porphyrins covalently linked to quinones. The first such models were reported in the late 1970 s. Kong and Loach prepared the ester-linked dyad 2 in 1978 [38], and the amide 3 was reported by Tabushi and coworkers in 1979 [39]. A large number of these P-Q systems have now appeared in the literature. The reader is referred to several reviews [13, 34, 40], including the recent review by Connolly and Bolton [41] for a complete compilation of these results. 

A. Ishida Y. Sakata T. Majima, Surface plasmon excitation of a porphyrin covalently linked to a gold surface. J. Chem. Soc., Chem. Comm 1998, 57-58. 

Figure 32-6 shows typical fluorescence emission maximum wavelengths for the cutaneous porphyrias. The plasma in VP contains porphyrin covalently bound to protein with a fluorescence emission maximum at 624 to 628 nm. In other porphyrias, porphyrin is noncovalently bound to albumin and hemopexin. A normal fluorescence emission scan in plasma from a patient with clinically active skin lesions excludes all cutaneous porphyrias as their cause. The scan may become normal in PCT and HCP as skin lesions heal, and the diagnosis may be missed unless individual porphyrins are also measured in urine and feces from such patients. In addition, the scan may be abnormal during an acute attack of AIP or HCP in the absence of skin lesions and is always abnormal in clinically manifest VP, whether skin lesions are present or not (Table 32-5). 

The photochemistry of a molecular triad consisting of a porphyrin covalently linked to a carotenoid polyene and a fullerene derivative has been studied at 20 K by time-resolved EMR spectroscopy following laser excitation (Carbonera et al., 1998). Excitation of the porphyrin yields a coupled radical pair with a carotenoid cation and a C o anion. The exchange interation in the pair has been determined to approx. 

Figure 7. Supramolecular cage-like compound 6 formed through 12 H bonds between two porphyrins covalently linked to 5-alkyluracil recognition groups, and two alkyltriaminopyrimidine units.

Figure 39. Supramolecular w tems 76 and 77 result from the coordination of porphyrin 64 to p-phenylene-bridged Zn(ll) porphyrin covalent dimers.

In the field of energy production, oxidative water splitting is an appealing process, especially if it can be achieved without noble metal catalysts. Thus, cobalt porphyrin, covalently bound to MWCNTs, gave a promising catalyst, in that it resulted in active electrochemical oxidation of water at low overpotential [209]. 

A suspension obtained from the water-solnble anionic mew-tetrakis(4-carboxyphenyl)porphyrin and MWCNTs was nsed as an optical probe for DNA detection [242]. The same target was achieved very recently, constructing a supramolecular assembly with the water-soluble anionic 5-(4-aminophenyl)-10,15,20-tris(4-sulfonatophenyl)porphyrin, covalently linked to MWCNTs and complexed with cyclodextrins (CD, either a-CD or P-CD) [243]. 

Orellana W. Catalytic activity toward oxygen reduction of transition metal porphyrins covalently linked to single-walled carbon nanotubes a density functional study. Phys Rev B 2011 84 155405/1-/1155405. 

In few cases linear chain structured polymeric metal complexes were prepared. A linear polymeric phthalocyanine 60 was obtained as film by the electrochemical polymerization of the corresponding monomer [260]. The synthesis of structural uniform ladder polymers 61 based on the hemiporphyrazine structures was achieved by a repetitive Diels-Alder reaction [261,262]. Recently, linear oligomeric porphyrines covalently connected via meso-meso-positions up to 128 units were synthesized [263]. 

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