Porphyrins general structure

In Table 1, the frequencies of various lines shown to be sensitive to the porphyrin s structure (8,10,15), are given for Ni(OEP) and Ni(PP) complexes in several time regimes and for several excitation wavelengths. As described below, the general results of the time-resolved spectra can be summarized as follows ... 

Dendritic derivatives of these macrocycles can be placed in the wider context of studies on metalloporphyrins with sterically hindered faces which have been designed in attempts to mimic the properties of heme proteins and chlorophylls, and there are suggestions that steric isolation of the metalloporphyrin nucleus is important in certain biological functions, The redox properties of metalloporphyrins are well-documented they are dominated by two, reversible one-electron transfers involving both the metal and the ligand. The first dendritic porphyrins of general structure 47 and their Zn complexes were reported by Inoue et al. who... 

While the typical bands of porphyrins with general structure 2 appear at 419, 515, 548, and 591 nm in the UV-vis absorption spectrum, the... 

The reductive nitrosylation of a synthetic iron porphyrin by HNO (193) proceeds with a reported rate constant of 1 x 107 A/-1 s However, this value was estimated based on a HNO dimerization rate constant of 8 x 109 M-1 s-1 (210), which is now considered to be 1000-fold lower [(8 x 106 A/-1 s-1 (106)]. The recalculated constant for the reaction of HNO with the porphyrin (3 x 10s AT V1) is similar to the estimated value of HNO addition to metMb. Synthetic porphyrins generally react 30-fold faster with NO (1 x 109M 1 s-1) than ferrous Mb [for a recent, thorough review see (44)] due to rate-limiting diffusion of NO through the protein. The similarity in rate constants for HNO with metMb and the ferric porphyrin suggests that the rate-limiting step in reductive nitrosylation is likely addition of HNO to the ferric metal, with little influence from the protein structure. 

Figure 1 shows the general structure of calixpyrroles. The basic ring structure resembles that of porphyrin. In the past, four pyrrole rings linked by methylene groups to form colourless macrocycles (that feature in the biosynthetic pathways to pyrrole pigments) were referred to as porphyrinogens [22], The term calix[4]pyrrole was later ascribed to these macrocycles and their synthetic derivatives because of their relation to calix[4]arenes [23],... 

The general structures of iron porphyrins are shown in Figure 1, together with the stractures of closely related ring systems, including iron chlorins and isobacteriochlorins, thiaporphyrins, tetraazaporphyrins, phthalocyanines, corroles, and texaphyrin. Examples of substituents present on commonly investigated natural and synthetic iron porphyrins are also included. 

Resins and asphaltenes are also of interest as a result of the fact that most of the heteroatoms reside in these fractions [7,16], Beaton and Bertolacini [5] report that about equal amounts of V and Ni reside in the resins as in the asphaltenes, while sulphur is concentrated in resins. The chemical associations between the heteroatoms and organic molecules are far from certain, although general descriptions in terms of porphyrin like structures have been advanced [5]. Sulphur appears to be easily accessible and thiophenic sulphur has been identified [8]. Vanadium is more accessible than nickel. 

Fig. 35 General structure of the phosphorus-porphyrins with axially hound phenolate-porphyrins by Maiya [81,102-104] and Tanaka and Segawa [105], M = VO(IV), Co(ll), Ni(ll), Cu(ll), Zn(ll), or P(V)...

Figure 5 General structure of the low-spin FeNO complexes (14 and 15, respectively) derived from the sterically encumbering porphyrin ligand 3,5-Me-BAFP.

Scheme 62 General structural formula of the porphyrin-furan and porphyrin-thiophene alternating copolymers (X = S or O) used in Ref. [131]...

Fig. 6.14 Generalized structure of porphyrin. The R groups represent different side groups attached to the porphyrin ring...

The name corrphycene for [18]porphyrin(2.1.0.1) is derived from the fact that these compounds combine structural elements from corrins/ corroles, porphyrins and acenes. Two general synthetic strategies have been developed for the final cyclization step of a linear tctrapyrrole leading to the macrotetracycle. 

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. 

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