Modified porphyrin

Preeminent in importance among the macro-cyclic complexes of Group 2 elements are the chlorophylls, which are modified porphyrin complexes of Mg. These compounds are vital to the process of photosynthesis in green plants (see Panel). Magnesium and Ca are also intimately... 

Synthesis, characterization, and chemistry of core-modified porphyrins and their nickel complexes 97NJC691. 

Metalloporphyrin reactivity and catalytic properties can also be controlled by modifications of the porphyrin core. Ni coordination chemistry of core-modified porphyrins has been reviewed.1791,1792 Several X-ray structures of four-, five-, and six-coordinate Ni11 complexes with oxa-, thia-, and dioxatetraarylporphyrins are known. 

The Stille Pd-catalyzed cross coupling has been employed in the synthesis of modified porphyrins [54, 55, 82]. For example, the union of dOialoporphyrins with tri-n-butylvinylstannane affords protoporphyrin IX in excellent yield [82]. 

You, Y. Gibson, S. L. Hilf, R. Davies, S. R. Oseroff, A. R. Roy, I. Ohulchanskyy, T. Y. Bergey, E. J. Detty, M. R. Water soluble, core-modified porphyrins. 3. Synthesis, photophysical properties, and in vitro studies of photosensitization, uptake, and localization with carboxylic add-substituted derivatives. J. Med. Chem. 2003, 46, 3734-3747. 

Jan-Frederik Gnichwitz, Mateusz Wielopolski, Kristine Hartnagel, Uwe Hartnagel, Dirk M. Guldi, Andreas Hirsch. Cooperativity and Tunable Excited State Deactivation Modular Self-Assembly of Depsipeptide Dendrons on a Hamilton Receptor Modified Porphyrin Platform. J. Am. Chem. Soc. 2008, 130, 8491. 

De Mateis F, Gibbs A. Drug-induced conversion of liver haem into modified porphyrins. Evidence for two classes of products. Biochem J 1980 187 285-288. 

Sol-gel preparation Siliceous framework (EtO)3 Si-modified porphyrin Battioni etal. (116)... 

Hayashi T, Takimura T, Ogoshi H (1995) Photoinduced singlet electron transfer in a complex formed from zinc myoglobin and methyl viologen artificial recognition by a chemically modified porphyrin. J Am Chem Soc 117 11606-11607... 

N-substituted iron porphyrins form upon treatment of heme enzymes with many xenobiotics. The formation of these modified hemes is directly related to the mechanism of their enzymatic reactivity. N-alkyl porphyrins may be formed from organometallic iron porphyrin complexes, PFe-R (a-alkyl, o-aryl) or PFe = CR2 (carbene). They are also formed via a branching in the reaction path used in the epoxidation of alkenes. Biomimetic N-alkyl porphyrins are competent catalysts for the epoxidation of olefins, and it has been shown that iron N-alkylporphyrins can form highly oxidized species such as an iron(IV) ferryl, (N-R P)Fe v=0, and porphyrin ir-radicals at the iron(III) or iron(IV) level of metal oxidation. The N-alkylation reaction has been used as a low resolution probe of heme protein active site structure. Modified porphyrins may be used as synthetic catalysts and as models for nonheme and noniron metalloenzymes. 

A very large class of macrocyclic thiophene derivatives is the thiophene-modified porphyrins. Several compounds (153-157) with ter- or quaterthiophene subunits <2006OL2325, 2006OL4847, 2007CC43> have been reported. All of them have been synthesized by the classical acid-catalyzed porphyrin synthesis. Solution and solid-state structures have been investigated using nuclear magnetic resonance (NMR) and ultraviolet (UV) spectroscopy, calculations, and X-ray structures. 

Porphyrin (see Porphyrin) molecules containing peripheral pyridine groups act as comers or 180° linkers depending on the positions of the pyridyl donor atoms. Reaction of (dppp)Pd(OTf)2 with (47) yields the molecular square (14) while a larger square (49) was obtained by employing a modified porphyrin (48) in which the two pyridine units are trans to each other (Scheme 15). The results of these reactions demonstrate that the ability of the molecular components to act as comers or linkers depends on their topologies. Bis-pyridyl-porphyrin (47) reacts with cis- and trani -(PhCN)2PdCl2 to yield the molecular squares (50) and (51), respectively, with varied dimensions. These squares have been characterized by NMR spectroscopy and mass spectrometry combined with UV-visible spectroscopy (see UV- Visible Spectroscopy) and vapor-phase osmometry. 

Metalloporphyrins and related compounds continue to attract attention as photosensitizers and as building blocks for construction of artificial lightharvesting arrays. The photophysical properties of several structurally modified porphyrins have been measured with a view to identifying new sensitizers for use in photodynamic therapy. The triplet state properties of porphyrins adsorbed onto the outer surface of vesicles have been describedand the fluorescence spectral properties of some amphiphilic porphyrins have been recorded. Similar studies have been carried out with halogenated tetraar-... 

In a recent example, aryl-carboxylic solubilization was used to solubilize core-modified porphyrins. Solubilizing aryl carboxylic functions were also replaced by their tetra-zole or 1,2,4-oxadiazolone bioisosteres in the design of second generation, benzodiazepine-derived, CCK-B antagonists (Figure 38.2). °... 

Another STM-UHV imaging success was the resolution of the internal structure of copper-phthalocyanine molecules. It was attained by Ogaki et al. under in situ conditions in 1996." They demonstrated an image of a specific modified porphyrin adsorbed on Ag(lll)-I surface, revealing the internal structure and molecular orientation in the ordered layer, as shown in Fig. 25. 

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