Porphyrin compounds

Reaction of free-base porphyrin compounds with iton(II) salts in an appropriate solvent results in loss of the two N—H protons and insertion of iron into the tetradentate porphyrin dianion ligand. Five-coordinate iton(III) porphyrin complexes (hemins), which usually have the anion of the iton(II) salt for the fifth or axial ligand, ate isolated if the reaction is carried out in the presence of air. Iron(II) porphyrin complexes (hemes) can be isolated if the reaction and workup is conducted under rigorously anaerobic conditions. Typically, however, iton(II) complexes are obtained from iton(III) porphyrin complexes by reduction with dithionite, thiolate, borohydtide, chromous ion, or other reducing agents. 

The last decade has seen the development of a rich and varied chemistry for or-ganometallic porphyrin complexes of the early transition metals (groups 3 and 4). However, there have been many fewer developments in the organometallic chemistry of the middle transition elements. Despite the paucity of its organometallic porphyrin compounds, molybdenum has played a very important role in... 

Hemoproteins, such as hemoglobin and the cytochromes, contain heme. Heme is an iron-porphyrin compound (Fe -protoporphyrin IX) in... 

A porphyrin compound with a 2,9-dimethyl- 1,10-phenanthroline functionality fused at the beta-pyrrole positions is a phthalocyanine analog, and formed a complex with zinc in the cavity and a further zinc binding to the phenanthroline group. The absorption and emission spectra of the compound with and without the external zinc demonstrated the strong effects of the second metal binding on the porphyrin 7r-system.840... 

Figure 5 Schematic representation of absorbance of porphyrin compounds in relation to tissue transmittance at various wavelengths (see text). The lowest energy band (Band I) is shown in each case, apart from the porphyrin spectrum (etio type shown) on the left. The transmittance curve refers to a fold of human scrotal sac 0.7 cm thick (Wan, S. Parrish, J. A. Anderson, R. R. Madden, M. Photochem. Photobiol. 1981, 34, 679-681). The broad feature at ca. 500-600 nm is ascribed to haemoglobin (reproduced by permission of the Royal Society of Chemistry from Chem. Soc. Rev. 1995, 24, 19-33).

Konishi et al.97 synthesized porphyrin compound 127. As shown in Scheme 4-44, asymmetric epoxidation of prochiral olefins such as styrene derivatives and vinyl naphthalene by iodosobenzene has been achieved by using this porphyrin complex as the catalyst in the presence of imidazole. The optically active epoxides were obtained with moderate ee. 

Cationic porphyrinic macrocycles, in particular the archetypical tetracationic, meso-telra-W-melhylpyridyl (porphyrin, have applications in biology, medicine, catalysis, and materials (95-103). Cationic tetraazaporphyrins, or porphyrazines, which represent a novel alternative and class of cationic porphyrinic compounds, were recently reported (37). 

Besides the applications of the electrophilicity index mentioned in the review article [40], following recent applications and developments have been observed, including relationship between basicity and nucleophilicity [64], 3D-quantitative structure activity analysis [65], Quantitative Structure-Toxicity Relationship (QSTR) [66], redox potential [67,68], Woodward-Hoffmann rules [69], Michael-type reactions [70], Sn2 reactions [71], multiphilic descriptions [72], etc. Molecular systems include silylenes [73], heterocyclohexanones [74], pyrido-di-indoles [65], bipyridine [75], aromatic and heterocyclic sulfonamides [76], substituted nitrenes and phosphi-nidenes [77], first-row transition metal ions [67], triruthenium ring core structures [78], benzhydryl derivatives [79], multivalent superatoms [80], nitrobenzodifuroxan [70], dialkylpyridinium ions [81], dioxins [82], arsenosugars and thioarsenicals [83], dynamic properties of clusters and nanostructures [84], porphyrin compounds [85-87], and so on. 

McGuinn WD, Baxter L, Pei L, et al. 1994. Antagonism of the lethal effects of cyanide by a synthetic water-soluble cobalt(III) porphyrin compound. Fundam Appl Toxicol 23(l) 76-80. 

Proton NMR studies of the methylated model porphyrin compound yielded the following results. When dissolved in the non polar... 

Porphyrin and porphyrin compounds— Congresses. 2. Porphyrin and porphyrin compounds— Spectra—Congresses. 

Eley DD (1940) The conversion of parahydrogen by porphyrin compounds, including hemoglobin. Trans Faraday Soc 35 500-505... 

Figure 5.12 Chiral self-aggregation of porphyrin compounds (adapted from Ribo et al., 2001, with kind permission), (a) The monomer and J-aggregates structures. (b). The outcome of rotating directions of the flask in the rotary evaporator, clockwise (CW) and anticlockwise (ACW), on the preparation of aggregates by concentration of a monomeric solution of the porphyrin. The corresponding CD spectra, showing the chirality signature, and the UV absorption bands of the J-aggregates are also shown. Notice that the two UV spectra are identical, whereas the two CD spectra are opposite to each other.

Variations on the vertical dipping technique have been utilized to construct films containing divalent metal ions. For example, the quartz crystal microbalance (QCM) has been used to evaluate the horizontal lifting method of CdSt LB Film construction (26). In this method, the QCM quartz plate was touched to monolayers compressed on a subphase and lifted horizontally. Y-type transfer (transfer ratio of 1) was demonstrated with two centrosymmetric monolayers deposited for each cycle. A combination of the vertical and horizontal dipping techniques has been utilized to prepare multilayer films from an amphiphilic porphyrin compound (27). 

Given the importance of porphyrin compounds, it was decided that it would be interesting to calculate the MCD spectra of some representative porphyrin complexes. 

Title Pyridine-Substituted Porphyrin Compounds and Methods of Use Thereof... 

Several photoreactions of porphyrin compounds proceed by triplet states.478 Chlorophyl is, of course, involved in some important photochemical reactions, and is known to form triplet states rather efficiently. However, it is not as yet certain how or whether its triplet state is involved in photosynthesis.479... 

Copper phthalocyanine is an example of a very important class of organic pigments. These are tetraazatetrabenzo derivatives of the porphyrin compounds discussed in Sections 20-9 and 25-8B. Copper phthalocyanine arises from condensation of four molecules of 1,2-benzenedicarbonitrile in the presence of copper metal at 200° ... 

Many studies have been carried out on the epoxidation of olefin compounds54-613 because epoxides are important starting materials for the synthesis of polymers. In laboratories, epoxides are synthesized by partial oxidation of olefins using iodosylbenzene, hypochlorite, or organic hydroperoxides as the oxidants. For these reactions, porphyrin compounds are often used as the catalysts. 62-653 peracetic acid is also known to be an efficient oxidant for the epoxidation of olefins66)... 

Some researchers have doubted whether nonporphyrin metal compounds exist at all in petroleum (Goulon et al., 1984 Berthe et al., 1984). This speculation is based on the similarities in spectral features of petroleum-bound metals and model-metal porphyrin compounds from selected petroleums under the examination of x-ray absorption, photoelectron, and laser desorption spectroscopies. Interpretation of spectra from these methods, however, is uncertain and difficult given the lack of sufficient data on model compounds, particularly nonporphyrin metals and in a petroleum environment or matrix. 

The occupancy of the d orbitals in high spin porphyrin compounds is of the type shown in Fig. 5.1 under the heading D4h. Such occupancy accounts for both... 

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