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Showing papers on "Porphyrin published in 1993"


Journal ArticleDOI
TL;DR: In this paper, a light-scattering experimental approach is described for detecting such extended aggregates of chomophores in which the radiation used is within an absorption maximum, specifically in the porphyrin Soret absorption region.
Abstract: Under appropriate conditions of concentration and ionic strength, trans-bis(N-methylpyridinium-4-yl)-diphenylporphine and its copper(II) derivative produce very large, bisignate circular dichroism signals in the Soret region when bound to DNA. The processes leading to these signals are shown to be highly cooperative. A new light-scattering experimental approach is described for detecting such extended aggregates of chomophores in which the radiation used is within an absorption maximum, specifically in the porphyrin Soret absorption region. Results from such resonance light-scattering experiments confirm that extended porphyrin aggregates form on the DNA, which, in contrast, remains dispersed

802 citations


Journal ArticleDOI
TL;DR: In this article, a water-soluble porphyrin, 5,10,15,20,tetra(4,sulfophenyl)porphyrin (H2TPPS44−), formed in acidified aqueous solutions, exhibits sharp and intense absorption bands at 491 and 707 nm.
Abstract: J aggregate of a water‐soluble porphyrin, 5,10,15,20‐tetra(4‐sulfophenyl)porphyrin (H2TPPS44−), formed in acidified aqueous solutions, exhibits sharp and intense absorption bands at 491 and 707 nm. These characteristic transitions, J bands, are of linear oscillators polarized in the long axis of rodlike aggregate. The molecules in the aggregate stack so as to lift the degeneracy of the porphyrin planar oscillator excited states. Measurements of flow‐induced linear dichroism, circular dichroism, magnetic circular dichroism, as well as polarized fluorescence excitation spectra provide evidence not only of linear oscillator character of the intense J band at 491 nm, but also of presence of another diffuse absorption band around at 420 nm polarized in the short axis of the aggregate, which is the counterpart of the 491 nm band of porphyrin Soret origin. Extrinsic circular dichroism is induced upon addition of L‐tartaric acid or by mechanical swirling flow in the period of aggregate growth. Resonance Raman spe...

446 citations


Journal ArticleDOI
TL;DR: Two kinds of biomimetic systems based on metalloporphyrin catalysts are able to perform the selective oxidation of alkanes as discussed by the authors, which are of the monooxygenase type and involve the transfer of an oxygen atom from high-valent metal-oxo active species to the alkane.

362 citations


Journal ArticleDOI
TL;DR: In this article, molecular packing in over 200 tetraarylporphyrin-based lattice clathrates reveals a strong conservation of host structure and several modes of intercalation are detected.
Abstract: Analysis of the molecular packing in over 200 tetraarylporphyrin-based lattice clathrates reveals a strong conservation of host structure. In most cases, formation of porphyrin-based clathrates can be viewed as arising from intercalation of guest molecules into pure host materials. Several modes of intercalation are detected, and characteristic of intercalate structures, staging is observed. Intercalate formation accounts for the relative insensitivity of the host structure to the nature and size of the guest species. The structural conservation observed in this large class of materials facilitates rational modification of the host lattice. Crystallographic data are provided for 75 new porphyrin-based clathrates

352 citations


Journal ArticleDOI
TL;DR: The equilibrium constants for association of ferrihemoproteins and NO are 1 order of magnitude larger than that of the water-soluble iron(III) porphyrin which is free from protein, suggesting that the proteins offset the forward and backward reaction rates in the equilibrium reactions.
Abstract: Author(s): Hoshino, M; Ozawa, K; Seki, H; Ford, PC | Abstract: Water-soluble iron(III) porphyrin and ferrihemoproteins (methemoglobin, metmyoglobin, oxidized cytochrome c, and catalase) associate with NO to yield the nitric oxide adducts The equilibrium constants for association of ferrihemoproteins and NO are 1 order of magnitude larger than that of the water-soluble iron(III) porphyrin which is free from protein, suggesting that the proteins offset the forward and backward reaction rates in the equilibrium reactions Nanosecond laser photolysis studies of the nitric oxide adducts of metmyoglobin, oxidized cytochrome c, and catalase, (NO)MbIII, (NO)CytIII, and (NO)CatIII, have been carried out The transient detected after laser flash photolysis of (NO)CatIII is identified as CatIII However, the transients observed for (NO)MbIII and (NO)CytIII at 50 ns after laser pulsing are ascribed to MbIIItr and CytIIItr, respectively, with the absorption spectra different from those of uncomplexed MbIII and CytIII In particular, the absorption spectrum of CytIIItr markedly differs from that of the uncomplexed CytIII The species MbIIItr and CytIIItr are found to change to MbIII and CytIII, respectively, within a few microseconds The quantum yields for the photodissociation of NO from nitric oxide adducts of ferrihemoproteins are 1 order of magnitude less than that from the NO adduct of the water-soluble iron(III) porphyrin, probably due to fast geminate recombination reaction of NO and ferrihemoprotein in a heme pocket The photochemistry of the nitric oxide adducts of hemoproteins and water-soluble iron(II) porphyrin is also described on the basis of laser phosolysis studies © 1993, American Chemical Society All rights reserved

281 citations


Journal Article
TL;DR: A series of RuII complexes were synthesized pdf417 activex crack with the deprotonated forms of polypyridine and porphyrin complexes in this paper, where the second part deals with rutheniumII poly pyridyl complexes linked.
Abstract: Amazon Photochemistry of Polypyridine and Porphyrin Complexes.The second part deals with rutheniumII polypyridyl complexes linked. Photochemistry of Polypyridine and Porphyrin Complexes Academic Press.A series of RuII complexes were synthesized pdf417 activex crack with the deprotonated forms of. Ruthenium coordination compounds containing polypyridyl ligands. Photochemistry and Photobiology, 2010, 86: 12301236.

262 citations


Journal ArticleDOI
TL;DR: In this article, the synthesis and characterization of covalently bound self-assembled monolayer thin films of 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (TPyP) and its derivatives on fused quartz and silicon [100] substrates having a native oxide layer are described.
Abstract: The synthesis and characterization of covalently bound self-assembled monolayer thin films of 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (TPyP) and its derivatives on fused quartz and silicon [100] substrates having a native oxide layer are described. The monolayer film consists of porphyrin macrocycle disk-like structures that were analyzed by UV-visible spectroscopy, X-ray photoelectron spectroscopy (XPS), and polarized FTIR-ATR measurements. One of the attractive features of these complexes is their large second-order nonlinear optical response, as expected for a strongly delocalized [pi]-electron system without inversion symmetry. Second-harmonic generation (SHG) measurements have been used to determine the absolute value of the dominant element of the nonlinear susceptibility, [chi]-zzz approximately 2 [times] 10[sup [minus]8] esu, the uniformity of these films, and the dispersion of the refractive indices. The average molecular orientation angle of the surface-bound chromophores was measured by both FTIR-ATR and SHG and found to be in good agreement. 31 refs., 3 figs.

168 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of the electron-withdrawing power of the substituents bound to a porphyrin ring on the electronic structures and reactivities of oxoiron(IV) porphrin π-cation radical complexes were studied by using 2,7,12,17,tetramethyl-3,8,13,18,18-tetraarylporphyrins (aryl=(1) mesityl, (2) 2-chloro-6-methylphenyl, 2,6-dichlorophen
Abstract: The effects of the electron-withdrawing power of the substituents bound to a porphyrin ring on the electronic structures and the reactivities of oxoiron(IV) porphyrin π-cation radical complexes were studied by using 2,7,12,17-tetramethyl-3,8,13,18-tetraarylporphyrins (aryl=(1) mesityl, (2) 2-chloro-6-methylphenyl, 2,6-dichlorophenyl, or 2,4,6-trichlorophenyl). The electronic structures of oxoiron(IV) porphyrin π-cation radicals were investigated by low-temperature UV-visible absorption spectroscopy and proton NMR measurements.

163 citations


Journal ArticleDOI
TL;DR: Systemic administration of ALA can induce effective tissue sensitization with protoporphyrin IX and appears to be a promising technique for PDT.
Abstract: The accumulation of endogenous porphyrins in rats following systemic administration of 5-aminolaevulinic acid (ALA) has been examined to assess the photosensitization characteristics of this technique for photodynamic therapy (PDT) and chemical extraction assays with fluorescence and absorbance detection of the porphyrin content have been carried out. We compared the results obtained using quantitative microfluorimetry on normal gastric and colonic tissues in rats at 0.5, 1, 2, 4 and 6 h and chemically induced duodenal tumours 2 and 4.5 h after intravenous administration of ALA at a dose of 200 mg kg-1. With chemical extraction followed by high performance liquid chromatography analysis, protoporphyrin IX (PpIX) was found to be the predominant porphyrin present, reaching peak levels of several microgrammes per gramme at 2-4 h in each type of tissue; a small amount of coproporphyrin was detected at 0.5 and 2 h in normal gastric mucosa and duodenal tumour respectively. Both the extraction assay and quantitative microfluorimetry showed that the porphyrin fluorescence builds up rapidly in the mucosal layers of the colon and stomach, reaching a maximum at 2 h, whereas lower fluorescence levels were found with a slower rate of accumulation in the corresponding muscularis layers. A significant PpIX content was found in the duodenal tumour, with a maximum of 7.1 micrograms g-1 4.5 h after ALA administration. We conclude that systemic administration of ALA can induce effective tissue sensitization with protoporphyrin IX and appears to be a promising technique for PDT.

145 citations


Journal ArticleDOI
TL;DR: Both the tin(IV) and indium(III) metalloporphyrin-based stationary phases exhibit useful selectivity for the separation of aromatic sulfonates and aromatic carboxylates.
Abstract: A tetraphenylporphyrin-based stationary phase for high-performance liquid chromatography is prepared by attaching a p-carboxyphenyl derivative of the porphyrin to aminopropyl silica gel through an amide bond. This stationary-phase support is used for the reversed-phase separation of several polycyclic aromatic hydrocarbons and is shown to exhibit novel shape selectivity toward planar aromatic solutes. Subsequent metalation of the immobilized tetraphenylporphyrin with either tin(IV) or indium(III) results in a stationary phase with anion-exchange characteristics. Both the tin(IV) and indium(III) metalloporphyrin-based stationary phases exhibit useful selectivity for the separation of aromatic sulfonates and aromatic carboxylates.

126 citations


Journal ArticleDOI
TL;DR: In this article, the kinetic isotope effects in alkane hydroxylations catalyzed by manganese and iron porphyrins have been studied with 1,3-dideuterioadamantane as substrate.
Abstract: Intramolecular kinetic isotope effects (KIEs) in alkane hydroxylations catalyzed by manganese and iron porphyrins have been studied with 1,3-dideuterioadamantane as substrate. This substrate is highly suitable for determination of primary isotope effects in metalloporphyrin-catalyzed hydroxylations: the high chemical reactivity of tertiary C-H (D) bonds avoids side reactions which complicate product analyses, and tertiary C-H and C-D bonds have the same steric and stereochemical environment. Kinetic isotope effects have been determined with adamantane-1,3-d 2 (98 atom % D) and iron and manganese complexes of meso-tetrakis(2,6-dichlorophenyl)porphyrin and meso-tetramesitylporphyrin [M III (TDCPP)Cl and M III (TMP)Cl,M III =Fe or Mn] as catalysts

Journal ArticleDOI
TL;DR: In this article, the first direct observation of the push effect on heterolytic and homolytic O-O bond cleavage steps of acylperoxoiron(III) porphyrin complexes was reported.
Abstract: The first direct observation of the push effect on heterolytic and homolytic ()-(bond cleavage steps of acylperoxoiron(III) porphyrin complexes is reported for a series of acylperoxoiron(III) porphyrins (5) having substituents at the meso-positions of the porphyrin ring. Transformation of 5 to the corresponding oxoferryl (O=Fe IV ) porphyrin cation radicals in methylene chloride at -80 o C by heterolytic O-O bond cleavage was found to be first order in [5].

Journal ArticleDOI
TL;DR: In this article, the synthesis and photophysical characterization of a series of quinone-substituted, phenyl-linked dimeric and trimeric porphyrin arrays suitable for the study of electron transfer within closely-coupled subunits is presented.
Abstract: The synthesis and photophysical characterization of a series of quinone-substituted, phenyl-linked dimeric and trimeric porphyrin arrays suitable for the study of electron transfer within closely-coupled subunits is presented. The excited singlet state of a porphyrin possessing a quinone substituent at a meso position is shortened to <350 fs due to electron donation to the appended quinone. Energy transfer between adjacent porphyrins occurs with a rate constant of ca. 10[sup 11] s[sup [minus]1], and the photon is immediately trapped by the proximal porphyrin. For the liner porphyrin trimer, the photon can transfer between distal and central porphyrins in an incoherent manner until it is trapped by the proximal porphyrin. These arrays represent interesting models for natural photosynthetic organisms since they combine light harvesting, energy migration and trapping, and photoinduced electron transfer in a single supramolecular entity. 46 refs., 6 figs., 1 tab.

Journal ArticleDOI
TL;DR: Alkali-mediated reaction of 5,10,15,20-tetrakis(3′,5′-dihydroxyphenyl)porphine with dendritic bromide gives the novel porphyrin covalently encapsulated into a huge dendrite cage (‘caged’ porphyrsin).
Abstract: Alkali-mediated reaction of 5,10,15,20-tetrakis(3′,5′-dihydroxyphenyl)porphine with dendritic bromide gives the novel porphyrin covalently encapsulated into a huge dendritic cage (‘caged’ porphyrin).

Journal ArticleDOI
TL;DR: The transition metal-directed threading of a molecular fragment containing a central chelate and an end-attached gold porphyrin into a presynthesized coordinating ring affords a general precursor to rotaxane-type structures as mentioned in this paper.
Abstract: The transition metal-directed threading of a molecular fragment containing a central chelate and an end-attached gold(III) porphyrin into a presynthesized coordinating ring affords a general precursor to rotaxane-type structures. After threading, construction of the second porphyrin acting as an efficient stopper affords a copper(I)-complexed [2]-rotaxane as well as a novel compartmental [3]-rotaxane. The latter compound consists of a three-porphyrin-containing molecular fragment threaded through two 30-membered rings. Quantitative demetalation of the copper(I)-completed [2]-rotaxane affords a free-ligand [2]-rotaxane. The two porphyrins are bulky enough to inhibit any process leading to separate fragments, the cycle and the thread

Journal ArticleDOI
TL;DR: In this paper, a general interpretation of hyperporphyrin spectra in terms of charge-transfer excited states, involving charge movement either into or out of the porphyrin ring, was presented.
Abstract: Successive protonation by trifluoroacetic acid of meso-tetraphenylporphyrin derivatives bearing one, two, or four p-dimethylamino groups gives rise to new types of spectra. With one free amino group, the spectrum of the centrally protonated porphyrin shows a strong far-red band, a broad, flat absorption in the visible, and a less intense Soret band. With two or more free amino groups, the Soret band of the centrally protonated porphyrin is further split into two components. Complete protonation, including the peripheral amino groups, in all cases restores the spectral structure of the unsubstituted tetraphenylporphyrin dication. The spectra of the dianions of tetraanilino- and tetraphenylporphyrins are also similar. These results, and the related behavior of p-oxyphenylporphyrins and protonated Schiff base porphyrins, lead to a general interpretation of hyperporphyrin spectra in terms of charge-transfer excited states, involving charge movement either into or out of the porphyrin ring. 26 refs., 4 figs., 2 tabs.

Journal ArticleDOI
TL;DR: A rotaxane has been built around a central copper(I) bis(1,10-phenanthroline) complex with gold(III) and zinc(II) porphyrins acting as terminal stoppers.
Abstract: A rotaxane has been built around a central copper(I) bis(1,10-phenanthroline) complex with gold(III) and zinc(II) porphyrins acting as terminal stoppers. Upon selective excitation of either porphyrin, rapid electron transfer occurs from the zinc porphyrin to the appended gold porphyrin. The copper(I) complex donates an electron to the resultant zinc porphyrin [pi]-radical cation, and the ground-state system is restored by relatively slow electron transfer from the gold porphyrin neutral radical to the copper(II) complex. The rates of the various electron-transfer steps observed with the rotaxane are compared to those occurring in closely related systems, and it is concluded that the copper(I) complex mediates photoinduced electron transfer between the terminal porphyrinic subunits but not the reverse reaction. A qualitative understanding of the electron-transfer rate is presented in terms of a simple orbital energy diagram involving through-bond electron or hole transfer. 39 refs., 3 figs., 2 tabs.

Journal ArticleDOI
TL;DR: In this article, the stabilities of various porphin analogue compounds such as unsubstituted and substituted phthalocyanines, tetraphenylporphyrin, naphthocyanine, and tetraazapor phyrin have been investigated.
Abstract: The stabilities of various porphin analogue compounds such as unsubstituted and substituted phthalocyanines, tetraphenylporphyrin, naphthalocyanine and tetraazaporphyrin have been investigated. The compounds were dissolved either in organic solvents or water. Electronic spectra in the visible region were recorded after the samples were kept either under inert gas or air in the dark and under illumination. The rate of decay of absorption is explained by a decomposition reaction which is of first-order kinetics with respect to the porphyrin concentration. Illumination, and the presence of oxygen, enhance the rate of decomposition. In general, an increase of the size of the ligand and an increase of the electron donating ability of substituents further enhance the rate of decomposition. Central metal ions with open shell arrangements of electrons favour the photodecomposition of the molecules. Thin solid films of phthalocyanines obtained by vapour deposition were investigated for their stability in contact with either air or an aqueous electrolyte. The influence of a cathodic bias potential was studied in the dark and under illumination. When compared to the dissolved molecules the crystalline solids turned out to be much more stable although, decomposition could be detected in a long-term photoelectrochemical experiment. Decomposition products were determined and appropriate mechanisms are discussed.


Journal ArticleDOI
TL;DR: In this article, the rectification and photovoltaic properties of Al/porphyrin/Au sandwich-type cell are improved by mixing Zntpp solid with o-chloranil.
Abstract: By mixing Zntpp solid with o-chloranil, the rectification and photovoltaic properties of Al/porphyrin/Au sandwich-type cell are improved (Zntpp: 5, 10, 15, 20-tetraphenylporphyrinatozinc). The improvement may be mainly attributable to an increase in the hole concentration as the majority carrier because of the electron transfer from Zntpp to o-chloranil in the ground state. In addition, by mixing H2tpp solid with o-chloranil, the short circuit photocurrent of the sandwich-type cell increases although the rectification property is hardly improved (H2tpp: 5, 10, 15, 20-tetraphenylporphyrin). The fluorescence intensity, the short circuit photocurrent and its temperature-dependence for various porphyrin solids mixed with o-chloranil are measured in order to clarify the photogeneration mechanism of charge carriers. The results suggest strongly that an exciplex formed between H2tpp and o-chloranil molecules contributes to the photogeneration of charge carriers.

Journal ArticleDOI
TL;DR: In this article, a set of rotaxanes has been constructed consisting of a 30-membered macrocyclic ring, incorporating a 2,9-diphenyl-1,10-phenanthroline residue, threaded onto a second 2, 9-dipphenyl, 1,10phenanthus residue with gold-(III) and zinc(II) porphyrins acting as terminal stoppers.
Abstract: A set of rotaxanes has been constructed consisting of a 30-membered macrocyclic ring, incorporating a 2,9-diphenyl-1,10-phenanthroline residue, threaded onto a second 2,9-diphenyl-1,10-phenanthroline residue with gold-(III) and zinc(II) porphyrins acting as terminal stoppers. The two chelating groups may be coordinated to copper(I) or zinc(II) cations or left free. Upon selective excitation of either porphyrin, rapid electron transfer occurs from the zinc porphyrin to the appended gold porphyrin and the ground state is restored by relatively slow reverse electron transfer. The rates of the various electron-transfer steps show a marked dependence on the molecular architecture and may be understood in terms of a frontier molecular orbital energy diagram involving through-bond electron or hole transfer

Journal ArticleDOI
TL;DR: The photochemistry of four chlorophyll-porphyrin-naphthoquinone molecules possessing both fixed distances and orientations between the three components is described in this paper.
Abstract: The photochemistry of four chlorophyll-porphyrin-naphthoquinone molecules possessing both fixed distances and orientations between the three components is described. These molecules consist of a methyl pyropheophorbide a or pyrochlorophyllide a that is directly bonded at its 3-position to the 5-position of a 2,8,12,18-tetraethyl-3,7,13,-17-tetramethylporphyrin, which is in turn bonded at its 15-position to a 2-triptycenenaphthoquinone. In addition, porphyrin-quinone compounds in which the chlorins are replaced by a p-tolyl group were also prepared as reference compounds. Selective metalation of the macrocycles with zinc gives the series ZCHPNQ, ZCZPNQ, HCZPNQ, HCHPNQ, HPNQ, and ZPNQ, where H, Z, C, P, and NQ denote free base, Zn derivative, chlorophyll, porphyrin, and naphthoquinone, respectively. Selective excitation of ZC in ZCZPNQ and ZCHPNQ, and HC in HCHPNQ dissolved in butyronitrile yields ZC[sup +]ZPNQ[sup [minus]], ZC[sup +]HPNQ[sup [minus]], and HC[sup +]HPNQ[sup [minus]] with rate constants of 1.0 [times] 10[sup 11], 9.0 [times] 10[sup 9], and 8.2 [times] 10[sup 9] s[sup [minus]1] respectively, while the corresponding ion-pair recombination rate constants are 1.4 [times] 10[sup 10], 4.0 [times] 10[sup 9], and 4.0 [times] 10[sup 9] s[sup [minus]1], respectively. The fact that ZCZPNQ possesses faster rates of charge separation than do ZCHPNQ and HCHPNQ is inconsistent with an electron transfer mechanism involvingmore » superexchange with virtual states possessing anionic character on the bridging porphyrin. The data support an electron transfer mechanism in which the lowest excited singlet state of the bridging porphyrin weakly mixes with the lowest excited singlet state of the chlorophyll. This mixed state crosses over to a charge transfer in which the bridging porphyrin is oxidized and the quinone is reduced. This charge transfer state then relaxes to yield the final state which possesses an oxidized chlorophyll and a reduced quinone. 58 refs., 10 figs., 1 tab.« less

Journal ArticleDOI
TL;DR: In this paper, the reaction of free-base porphyrins (H 2 Por=octaethylporphyrin (OEP), meso-tetraphenyl (TPP) and TTP) with 2 equiv of MN(SiMe 3 ) 2 (M=Li, Na, K) in THF or dimethoxyethane (DME) yields dimetal salts of empirical formula M 2 (THF) 4 Por and M 2 DME 2 Por.
Abstract: Reaction of free-base porphyrins (H 2 Por=octaethylporphyrin (OEP), meso-tetraphenylporphyrin (TPP), meso-tetra-p-tolylporphyrin (TTP), meso-tetrakis(4-tert-butylphenyl)porphyrin (TBPP), meso-tetrakis(3,4,5-trimethoxyphenyl)porphyrin (TMPP)) with 2 equiv of MN(SiMe 3 ) 2 (M=Li, Na, K) in THF or dimethoxyethane (DME) yields dimetal salts of empirical formula M 2 (THF) 4 Por and M 2 (DME) 2 Por, respectively.

Journal ArticleDOI
TL;DR: In this article, a shish kebab oligomer was obtained by first inserting a ruthenium chloro carbonyl complex in tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin.
Abstract: The association of pentaammineruthenium(II) with the reducible ligand 4,4[prime]-azopyridine leads to a pH-induced redox reaction in which ruthenium is oxidized to the III state, while 4,4[prime]-azopyridine is reduced to hydrazopyridine. In this process, the conjugated ligand is transformed in a nonconjugated one, with loss of its intramolecular electron-transfer properties. In order to exploit this control of an intramolecular electron transfer by a protonation process, the authors have prepared shish kebab oligomers by first inserting a ruthenium chloro carbonyl complex in tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin. The resulting Ru(CO)(porphyrin) complex is photochemically decarbonylated in the presence of bridging ligands (4,4[prime]-azopyridine or pyrazine). Oligomers are thus obtained, which can be oxidized by iodine, giving rise to intervalence transitions between ruthenium(II) and -(III) in the near-infrared. This provides a convenient way to monitor electron transfer along the oligomer chain. In the case of 4,4[prime]-azopyridine, the pH-induced redox reaction is again observed. Starting from a homovalent ruthenium(II) chain, this gives the possibility to switch on or off the intervalence transition by a protonation/deprotonation reaction. 17 refs., 8 figs. 2 tabs.


Journal ArticleDOI
TL;DR: In this article, the surface-enhanced resonance Raman scattering (SERRS) spectra of free base 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TPPC 4 ) and of its silver complex, Ag(II)TPPC4, have been investigated under conditions of direct adsorption of the porphyrin on the surface of Ag colloid and attachment of the poly(oxyethylene)-poly(polyethylene) via a nonionic surfactant, Triton
Abstract: Surface-enhanced resonance Raman scattering (SERRS) spectra of free base 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TPPC 4 ) and of its silver complex, Ag(II)TPPC 4 , have been investigated under conditions of (I) the direct adsorption of the porphyrin on the surface of Ag colloid and (II) the attachment of the porphyrin to the surface of Ag colloid via a nonionic surfactant, Triton X-100 (p-(1,1,3,3-tetramethylbutyl)phenylpoly(oxyethylene)), functioning as a molecular spacer. For both types of porphyrin adsorption, the mechanisms of the SERS-active system formation have been elucidated

Journal ArticleDOI
TL;DR: In this paper, a bimolecular Diels-Alder reaction is accelerated substantially and stereoselectively by binding diene and dienophile within the cavity of a cyclic metalloporphyrin trimer.
Abstract: A bimolecular Diels–Alder reaction is accelerated substantially and stereoselectively by binding diene and dienophile within the cavity of a cyclic metalloporphyrin trimer.

Journal ArticleDOI
TL;DR: The compound does not appear to affect the metabolic disposition of preformed bilirubs but inhibits biliary bilirubin excretion derived from the metabolism of endogenous or exogenous heme, and some of the effect of Sn-PP on naturally occurring or experimentally induced jaundice in animals reflects diversion of heme to nonheme to oxygenase-dependent pathways of he me metabolism.
Abstract: Although free porphyrins occur in nature in small quantities, no known function has been assigned to them. In contrast, heme and cobalamin, which are Fe and Co chelates of porphyrins or porphyrin derivatives, respectively, carry out crucial biological functions. Heme is the prosthetic group for a number of hemoproteins. These include myoglobin and hemoglobin, which carry out oxygen binding or transport; mitochondrial cytochromes aa3, b, c, and c3, which are important in transferring electrons; microsomal cytochrome P-450, which catalyzes mixed-function oxidations; catalase, which decomposes H2O2; peroxidase, which activates H2O2; and tryptophan pyrrolase, which catalyzes the oxidation of tryptophan. Recently, heme has also been shown to be the prosthetic group of prostaglandin and peroxide synthetase and indoleamine dioxygenase. The elegant studies of the biochemical pathway for the formation of heme demonstrated the arrangement in the porphyrin macrocycle of the carbon and nitrogen atoms originating from the eight glycine and the succinic acid molecule that are the precursors of porphyrins. There are eight enzymes involved in the synthesis of heme. The first and last three of these enzymes are localized in mitochondria, while the intermediate enzymes are localized in cytosol. The catalytic site of HMOX recognizes metalloporphyrins with central metal atoms other than iron; it favors some of these metalloporphyrins over heme as a potential substrate, sometimes by a large factor, permitting the synthetic heme analogue to serve as a potent competitive inhibitor of HMOX reaction. Since these synthetic metalloporphyrins do not bind molecular oxygen, they are not metabolically degraded by ring rupture and do not add to the body pool of bile pigment. One possible consequence of this competitive inhibition of heme degradation is suppression of bile pigment formation to such a degree that excessive plasma levels of bilirubin may be diminished. The studies of Drummond and Kappas (1981) and later studies in rats, mice, monkeys, and man, and also our studies have proved the latter phenomenon. The compound does not appear to affect the metabolic disposition of preformed bilirubin but inhibits biliary bilirubin excretion derived from the metabolism of endogenous or exogenous heme. Whether some of the effect of Sn-PP on naturally occurring or experimentally induced jaundice in animals reflects diversion of heme to nonheme to oxygenase-dependent pathways of heme metabolism, or whether a pathway which is normally latent becomes activated concurrent with HMOX inhibition is not known.(ABSTRACT TRUNCATED AT 400 WORDS)


Journal ArticleDOI
TL;DR: In this article, the authors describe the oxidation of an α,β-diarylpropane lignin dimer model and other dimethoxyarenes by several iron porphyrin-based biomimetic systems.
Abstract: This paper describes the oxidation of an α,β-diarylpropane lignin dimer model and other dimethoxyarenes by several iron porphyrin-based biomimetic systems. From 1-(3,4-dimethoxyphenyl)-2-phenylpropanol (1), three types of products are identified: the 3,4-dimethoxybenzaldehyde derived from the C α -C β cleavage of the propyl side chain and either quinones or muconic dimethyl esters resulting from oxidations at the level of the dimethoxyaryl group. The selectivity of the reaction is discussed with respect to the nature and reactivity of the high-valent iron-oxo species formed upon reaction of the oxidants, H 2 O 2 or magnesium monoperoxyphthalate (MMP), with the iron porphyrins