Sample records for halogenated iron porphyrins

  1. Model studies in cytochrome P-450-mediated toxicity of halogenated compounds: radical processes involving iron porphyrins.

    PubMed Central

    Brault, D

    1985-01-01

    Haloalkane toxicity originates from attack on biological targets by reactive intermediates derived from haloalkane metabolism by a hemoprotein, cytochrome P-450. Carbon-centered radicals and their peroxyl derivatives are most likely involved. The reactions of iron porphyrin--a model for cytochrome P-450--with various carbon-centered and peroxyl radicals generated by pulse radiolysis are examined. Competition between iron porphyrin and unsaturated fatty acids for attack by peroxyl radicals is pointed out. These kinetic data are used to derive a model for toxicity of haloalkanes with particular attention to carbon tetrachloride and halothane. The importance of local oxygen concentration and structural arrangement of fatty acids around cytochrome P-450 is emphasized. PMID:3007100

  2. Stabilization of higher-valent states of iron porphyrin by hydroxide and methoxide ligands: electrochemical generation of iron(IV)-oxo porphyrins.

    PubMed Central

    Lee, W A; Calderwood, T S; Bruice, T C

    1985-01-01

    An electrochemical study of hydroxide- and methoxide-ligated iron(III) tetraphenylporphyrins possessing ortho-phenyl substituents that block mu-oxo dimer formation has been carried out. Ligation by these strongly basic oxyanions promotes the formation of iron(IV)-oxo porphyrins upon one-electron oxidation. Further one-electron oxidation of the latter provides the iron(IV)-oxo porphyrin pi-cation radical. These results are discussed in terms of chemical model studies and the enzymatic intermediate compounds I and II of the peroxidases. PMID:3859865

  3. The synthesis of chlorophyll-a biosynthetic precursors and methyl substituted iron porphyrins

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Matera, K.M.

    1988-01-01

    The biosynthetic intermediates were incubated in a plant system. The activity levels calculated show that magnesium 6-acrylate porphyrins and one of the magnesium 6-{beta}-hydroxypropionate porphyrins are not intermediates. In addition, plant systems incubated with {sup 18}O{sub 2} were found to synthesize magnesium 2,4-divinyl pheoporphyrin-a{sub 5} incorporated with {sup 18}O at the 9-carbonyl oxygen. Mass spectroscopy confirmed the presence of the oxygen label, thus eliminating one of two hypothesized pathways to chlorophyll-a. An overall description is given of iron porphyrins and iron porphyrin containing proteins. The function of the propionic side chains of the heme prosthetic group during electron transport reactionsmore » will be investigated. The synthesis of a series of iron(III) hexamethyl porphyrins with increasingly longer substituents in the remaining two peripheral positions of the porphyrin is described. Models for NMR studies of iron chlorin containing enzymes are discussed. Iron(III) pyropheophorbide-a and methyl pyropheophorbide-a were synthesized in addition to 5-CD{sub 3}, 10-CD{sub 2} iron(III) pyropheophorbide-a and methyl pyropheophorbide-a. Together, these pyropheophorbides were used to assign NMR resonances and ultimately provide a model for other iron chlorins. The synthesis of nickel(II) anhydro-mesorhodoporphyrin from zinc(III) anhydromesorhodochlorin is described; this nickel porphyrin was used as a standard for ring current calculations of reduced nickel analogs of anhydromesorhodoporphyrin.« less

  4. Disproportionation of hydroxylamine by water-soluble iron(III) porphyrinate compounds.

    PubMed

    Bari, Sara E; Amorebieta, Valentín T; Gutiérrez, María M; Olabe, José A; Doctorovich, Fabio

    2010-01-01

    The reactions of hydroxylamine (HA) with several water-soluble iron(III) porphyrinate compounds, namely iron(III) meso-tetrakis-(N-ethylpyridinium-2yl)-porphyrinate ([Fe(III)(TEPyP)](5+)), iron(III) meso-tetrakis-(4-sulphonatophenyl)-porphyrinate ([Fe(III)(TPPS)](3-)), and microperoxidase 11 ([Fe(III)(MP11)]) were studied for different [Fe(III)(Porph)]/[HA] ratios, under anaerobic conditions at neutral pH. Efficient catalytic processes leading to the disproportionation of HA by these iron(III) porphyrinates were evidenced for the first time. As a common feature, only N(2) and N(2)O were found as gaseous, nitrogen-containing oxidation products, while NH(3) was the unique reduced species detected. Different N(2)/N(2)O ratios obtained with these three porphyrinates strongly suggest distinctive mechanistic scenarios: while [Fe(III)(TEPyP)](5+) and [Fe(III)(MP11)] formed unknown steady-state porphyrinic intermediates in the presence of HA, [Fe(III)(TPPS)](3-) led to the well characterized soluble intermediate, [Fe(II)(TPPS)NO](4-). Free-radical formation was only evidenced for [Fe(III)(TEPyP)](5+), as a consequence of a metal centered reduction. We discuss the catalytic pathways of HA disproportionation on the basis of the distribution of gaseous products, free radicals formation, the nature of porphyrinic intermediates, the Fe(II)/Fe(III) redox potential, the coordinating capabilities of each complex, and the kinetic analysis. The absence of NO(2)(-) revealed either that no HAO-like activity was operative under our reaction conditions, or that NO(2)(-), if formed, was consumed in the reaction milieu.

  5. Ab initio study on the molecular recognition by metalloporphyrins: CO interaction with iron porphyrin

    NASA Astrophysics Data System (ADS)

    Han, Seungwu; Cho, Kyeongjae; Ihm, Jisoon

    1999-02-01

    We have performed ab initio pseudopotential calculations to study the effects of structural deformations of iron porphyrin on the configuration of a carbon monoxide (CO) attached to it. We have considered two proximal deformations around the heme group: (i) rotation of a pyrrole ring in the iron porphyrin, and (ii) rotation of the imidazole side chain bound to the iron atom. We have identified induced changes of the atomic geometry and the electronic structure of the iron porphyrin-CO complex, and the results elucidate the microscopic nature of the CO interaction with the iron porphyrin. Implications on the controversies over the binding angle of the CO molecule on the iron porphyrin under different circumstances are discussed. A potential application to the simulation-based chemical sensor design is also discussed.

  6. Heterogeneous biomimetic catalysis using iron porphyrin for cyclohexane oxidation promoted by chitosan

    NASA Astrophysics Data System (ADS)

    Huang, Guan; Liu, Yao; Cai, Jing Li; Chen, Xiang Feng; Zhao, Shu Kai; Guo, Yong An; Wei, Su Juan; Li, Xu

    2017-04-01

    This study investigates how ligands modulate metalloporphyrin activity with the goal of producing a practical biomimetic catalyst for use in the chemical industry. We immobilized iron porphyrinate [iron-tetrakis-(4-sulfonatophenyl)-porphyrin; Fe(III) (TPPS)] on powdered chitosan (pd-CTS) to form an immobilized catalyst Fe(III) (TPPS)/pd-CTS, which was characterized using modern spectroscopic techniques and used for catalytic oxidation of cyclohexane with O2. Amino coordination to iron porphyrin in Fe(III) (TPPS)/pd-CTS altered the electron cloud density around the iron cation, probably by reducing the activation energy of Fe(III) (TPPS) and raising the reactivity of the iron ion catalytic center, thereby improving the catalytic efficiency. One milligram of Fe(III) (TPPS) catalyst can be reused three times for the oxidation reaction to yield an average of 22.9 mol% of cyclohexanone and cyclohexanol.

  7. Detection of iron-porphyrin proteins with a biochemiluminescent method in search of extraterrestrial life.

    PubMed

    Sotnikov, G G

    1970-01-01

    Iron-porphyrin proteins (catalase, peroxidase, hemoglobin, cytochrome C) represent an important group of redoxenzymes which have vitally important functions in micro-organisms. A biochemiluminescent method was employed for the detection of iron-porphyrin proteins. The reaction of luminol oxidation with H2O2 is accompanied by chemiluminescence. The rate of hydrogen peroxide decomposition increased 10(5)-10(7) -fold in the presence of the above enzymes as compared with ferrous (or ferric) ions. Possible application of this reaction for the detection of iron-porphyrin proteins of microbial origin was studied. Other authors have suggested this reaction for the detection of extraterrestrial life. Kinetics of the above reaction in the presence of iron-porphyrin proteins were shown to differ both in amplitude and duration of the signal from the pattern observed in the presence of non-hemin catalysts. The reaction pattern in the presence of mixed-soil populations is similar to those observed with pure bacterial cultures and individual iron-porphyrin proteins. Photometric tests revealed that among preparations studied the addition of 0.01% lysozyme was the most effective in destroying cell walls in microbial populations. However, removal of cell walls is not a necessary prerequisite for the detection of iron porphyrin since, for effective luminol oxidation with H2O2 the medium should be kept at pH 12.0. Pretreatment of microbial suspensions with ultrasound increased 2-fold the total signal due to iron porphyrins. The above method gives a reproducible signal indicating the presence of iron porphyrins when sterile nutrient media were innoculated with desert soil samples (Repeteck, Kara-Kum) and incubated for 13 hr. The device was able to detect the presence of no less than 10(5) - 10(6) cells per ml. The addition of limonite (Fe2O3 X nH2O) does not result in the appearance of an appreciable signal in the luminol + H2O2 system.

  8. [New iron-porphyrin/vanadium-substituted polyoxometalate catalyst: synthesis, characterization and catalytic activity].

    PubMed

    Dong, Xiao-li; Zhang, Zhen-cheng; An, Qing-da; Zhang, Shao-yin; Wang, Shao-jun

    2007-12-01

    A new kind of iron-porphyrin/vanadium-substituted polyoxometalate coordination compound was synthesized by the ion exchange reaction of FeTTMAPPI and H5PMo10V2o40 in solution. The new catalyst was characterized by IR spectrometry and UV-Vis spectrometry. As an excellent catalyst, its effects on benzene hydroxylation and catalytic capabilities were studied with H2O2 solution as the oxidant. The results indicated that the products contained the conjugated structure of porphyrin and the cage structure of polyoxometalate, the V atom in polyoxometalate is the main centre of catalytic activity, meanwhile the presence of iron-porphyrin could increase its catalytic activity greatly.

  9. Porphyrins

    DOEpatents

    Wijesekera, T.; Lyons, J.E.; Ellis, P.E. Jr.

    1996-11-05

    The invention comprises new compositions of matter, which are iron, manganese, cobalt or ruthenium complexes of porphyrins having hydrogen, haloalkyl or haloaryl groups in meso positions, two of the opposed meso atoms or groups being hydrogen or haloaryl, and two of the opposed meso atoms or groups being hydrogen or haloalkyl, but not all four of the meso atoms or groups being hydrogen. The invention also comprises new compositions of matter in which all four of the meso positions are substituted with haloalkyl groups and the beta positions are substituted with halogen atoms. A new method of synthesizing porphyrinogens is also provided. The novel compositions and others made according to the process of the invention are useful as hydrocarbon conversion catalysts; for example, for the oxidation of alkanes and the decomposition of hydroperoxides.

  10. Porphyrins

    DOEpatents

    Wijesekera, Tilak; Lyons, James E.; Ellis, Jr., Paul E.

    1996-01-01

    The invention comprises new compositions of matter, which are iron, manganese, cobalt or ruthenium complexes of porphyrins having hydrogen, haloalkyl or haloaryl groups in meso positions, two of the opposed meso atoms or groups being hydrogen or haloaryl, and two of the opposed meso atoms or groups being hydrogen or haloalkyl, but not all four of the meso atoms or groups being hydrogen. The invention also comprises new compositions of matter in which all four of the meso positions are substituted with haloalkyl groups and the beta positions are substituted with halogen atoms. A new method of synthesizing porphyrinogens is also provided. The novel compositions and others made according to the process of the invention are useful as hydrocarbon conversion catalysts; for example, for the oxidation of alkanes and the decomposition of hydroperoxides.

  11. Iron(II) porphyrins induced conversion of nitrite into nitric oxide: A computational study.

    PubMed

    Zhang, Ting Ting; Liu, Yong Dong; Zhong, Ru Gang

    2015-09-01

    Nitrite reduction to nitric oxide by heme proteins was reported as a protective mechanism to hypoxic injury in mammalian physiology. In this study, the pathways of nitrite reduction to nitric oxide mediated by iron(II) porphyrin (P) complexes, which were generally recognized as models for heme proteins, were investigated by using density functional theory (DFT). In view of two type isomers of combination of nitrite and Fe(II)(P), N-nitro- and O-nitrito-Fe(II)-porphyrin complexes, and two binding sites of proton to the different O atoms of nitrite moiety, four main pathways for the conversion of nitrite into nitric oxide mediated by iron(II) porphyrins were proposed. The results indicate that the pathway of N-bound Fe(II)(P)(NO2) isomer into Fe(III)(P)(NO) and water is similar to that of O-bound isomer into nitric oxide and Fe(III)(P)(OH) in both thermodynamical and dynamical aspects. Based on the initial computational studies of five-coordinate nitrite complexes, the conversion of nitrite into NO mediated by Fe(II)(P)(L) complexes with 14 kinds of proximal ligands was also investigated. Generally, the same conclusion that the pathways of N-bound isomers are similar to those of O-bound isomer was obtained for iron(II) porphyrin with ligands. Different effects of ligands on the reduction reactions were also found. It is notable that the negative proximal ligands can improve reactive abilities of N-nitro-iron(II) porphyrins in the conversion of nitrite into nitric oxide compared to neutral ligands. The findings will be helpful to expand our understanding of the mechanism of nitrite reduction to nitric oxide by iron(II) porphyrins. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Nitrous-acid-mediated synthesis of iron-nitrosyl-porphyrin: pH-dependent release of nitric oxide.

    PubMed

    Bhuyan, Jagannath; Sarkar, Sabyasachi

    2012-11-01

    Two iron-nitrosyl-porphyrins, nitrosyl[meso-tetrakis(3,4,5-trimethoxyphenylporphyrin]iron(II) acetic acid solvate (3) and nitrosyl[meso-tetrakis(4-methoxyphenylporphyrin]iron(II) CH(2)Cl(2) solvate (4), were synthesized in quantitative yield by using a modified procedure with nitrous acid, followed by oxygen-atom abstraction by triphenylphosphine under an argon atmosphere. These nitrosyl porphyrins are in the {FeNO}(7) class. Under an argon atmosphere, these compounds are relatively stable over a broad range of pH values (4-8) but, under aerobic conditions, they release nitric oxide faster at high pH values than that at low pH values. The generated nitric-oxide-free iron(III)-porphyrin can be re-nitrosylated by using nitrous acid and triphenylphosphine. The rapid release of NO from these Fe(II) complexes at high pH values seems to be similar to that in nitrophorin, a nitric-oxide-transport protein, which formally possesses Fe(III). However, because the release of NO occurs from ferrous-nitrosyl-porphyrin under aerobic conditions, these compounds are more closely related to nitrobindin, a recently discovered heme protein. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Metal complexes of substituted Gable porphyrins as oxidation catalysts

    DOEpatents

    Lyons, James E.; Ellis, Jr., Paul E.; Wagner, Richard W.

    1996-01-01

    Transition metal complexes of Gable porphyrins having two porphyrin rings connected through a linking group, and having on the porphyrin rings electron-withdrawing groups, such as halogen, nitro or cyano. These complexes are useful as catalysts for the oxidation of organic compounds, e.g. alkanes.

  14. Iron Mineral Catalyzed C-H Activation As a Potential Pathway for Halogenation Processes

    NASA Astrophysics Data System (ADS)

    Tubbesing, C.; Schoeler, H. F.; Benzing, K.; Krause, T.; Lippe, S.; Rudloff, M.

    2014-12-01

    Due to increasing drinking water demand of mankind and an expected climate change the impact of salt lakes and salt deserts will increase within the next decades. Furthermore, a rising sea level influences coastal areas like salt marshes and abets processes which will lead to elevated organohalogen formation. An additional increase of the global warming potential, of particle formation and stratospheric ozone depletion is expected. Understanding these multifaceted processes is essential for mankind to be prepared for these alterations of the atmosphere. For example, Keppler et al. (2000) described the production of volatile halogenated organic compounds via oxidation of organic matter driven by ferric iron. However, the formation of long-chained alkyl halides in salt lakes is yet undisclosed. Despite the relative "inertness" of alkanes a direct halogenation of these compounds might be envisaged. In 2005 Vaillancourt et al. discovered a nonheme iron enzyme which is able to halogenate organic compounds via generating the high valent ferryl cation as reaction center. Based on various publications about C-H activation (Bergman, 2007) we postulate a halogenation process in which an iron containing minerals catalyse the C-H bond cleavage of organic compounds in soils. The generated organic radicals are highly reactive towards halides connected to the iron complex. We suggest that next to diagenetically altered iron containing enzymes, minerals such as oxides, hydroxides and sulfides are involved in abiotic halogenation processes. We applied the amino acid methionine as organic model compound and soluble iron species as reactants. All samples were incubated in aqueous phases containing various NaCl concentrations. As a result various halogenated ethanes and ethenes were identified as reaction products. References Bergman, R. G. (2007) Nature, 446(7134) 391-393 Keppler, F., et al. (2000) Nature, 403(6767) 298-301 Vaillancourt, F. H., et al. (2005) Nature, 436(7054) 1191-1194

  15. Metal complexes of substituted Gable porphyrins as oxidation catalysts

    DOEpatents

    Lyons, J.E.; Ellis, P.E. Jr.; Wagner, R.W.

    1996-01-02

    Transition metal complexes of Gable porphyrins are disclosed having two porphyrin rings connected through a linking group, and having on the porphyrin rings electron-withdrawing groups, such as halogen, nitro or cyano. These complexes are useful as catalysts for the oxidation of organic compounds, e.g. alkanes.

  16. Fibrous materials on polyhydroxybutyrate and ferric iron (III)-based porphyrins basis: physical-chemical and antibacterial properties

    NASA Astrophysics Data System (ADS)

    Olkhov, A.; Lobanov, A.; Staroverova, O.; Tyubaeva, P.; Zykova, A.; Pantyukhov, P.; Popov, A.; Iordanskii, A.

    2017-02-01

    Ferric iron (III)-based complexes with porphyrins are the homogenous catalysts of auto-oxidation of several biogenic substances. The most perspective carrier for functional low-molecular substances is the polymer fibers with nano-dimensional parameters. Application of natural polymers, poly-(3-hydroxybutyrate) or polylactic acid for instance, makes possible to develop fiber and matrice systems to solve ecological problem in biomedicine The aim of the article is to obtain fibrous material on poly-(3-hydroxybutyrate) and ferric iron (III)-based porphyrins basis and to examine its physical-chemical and antibacterial properties. The work is focused on possibility to apply such material to biomedical purposes. Microphotographs of obtained material showed that addition of 1% wt. ferric iron (III)-based porphyrins to PHB led to increased average diameter and disappeared spindly structures in comparison with initial PHB. Biological tests of nonwoven fabrics showed that fibers, containing ferric iron (III)-based tetraphenylporphyrins, were active in relation to bacterial test-cultures. It was found that materials on polymer and metal complexes with porphyrins basis can be applied to production of decontamination equipment in relation to pathogenic and opportunistic microorganisms.

  17. Electrochemical behavior of meso-substituted iron porphyrins in alkaline aqueous media

    NASA Astrophysics Data System (ADS)

    Berezina, N. M.; Bazanov, M. I.; Maksimova, A. A.; Semeikin, A. S.

    2017-12-01

    The effect meso-substitution in iron porphyrin complexes has on their redox behavior in alkaline aqueous solutions is studied via cyclic voltammetry. The voltammetric features of the reduction of iron pyridylporphyrins suggest that the sites of electron transfer lie at the ligand, the metal ion, and the pyridyl moieties. The electron transfer reactions between the different forms of these compounds, including the oxygen reduction reaction they mediate, are outlined to show the sequence and potential ranges in which they occur in alkaline aqueous media. Under our experimental conditions, the iron porphyrins exist as μ-oxo dimmers whose activity for the electrocatalytic reduction of oxygen displays a considerable dependence on the nature of the substitutents and nitrogen isomerization (for pyridylporphyrins) and grows in the order (Fe( ms-Ph)4P)2O, (Fe[ ms-(Py-3)Ph3]P)2O, (Fe[ ms-(Py-4)4]P)2O, and (Fe[ ms-(Py-3)4]P)2O.

  18. Porphyrins and their synthesis from dipyrromethanes and aldehydes

    DOEpatents

    Wijesekera, Tilak; Lyons, James E.; Ellis, Jr., Paul E.

    1998-01-01

    The invention comprises new compositions of matter, which are iron, manganese, cobalt or ruthenium complexes of porphyrins having hydrogen, haloalkyl or haloaryl groups in meso positions, two of the opposed meso atoms or groups being hydrogen or haloaryl, and two of the opposed meso atoms or groups being hydrogen or haloalkyl, but not all four of the meso atoms or groups being hydrogen. The invention also comprises new compositions of matter in which all four of the meso positions are substituted with haloalkyl groups and the beta positions are substituted with halogen atoms. A new method of synthesizing porphyrinogens is also provided.

  19. Porphyrins and their synthesis from dipyrromethanes and aldehydes

    DOEpatents

    Wijesekera, T.; Lyons, J.E.; Ellis, P.E. Jr.

    1998-06-02

    The invention comprises new compositions of matter, which are iron, manganese, cobalt or ruthenium complexes of porphyrins having hydrogen, haloalkyl or haloaryl groups in meso positions, two of the opposed meso atoms or groups being hydrogen or haloaryl, and two of the opposed meso atoms or groups being hydrogen or haloalkyl, but not all four of the meso atoms or groups being hydrogen. The invention also comprises new compositions of matter in which all four of the meso positions are substituted with haloalkyl groups and the beta positions are substituted with halogen atoms. A new method of synthesizing porphyrinogens is also provided.

  20. Cis-dicarbonyl binding at cobalt and iron porphyrins with saddle-shape conformation.

    PubMed

    Seufert, Knud; Bocquet, Marie-Laure; Auwärter, Willi; Weber-Bargioni, Alexander; Reichert, Joachim; Lorente, Nicolás; Barth, Johannes V

    2011-02-01

    Diatomic molecules attached to complexed iron or cobalt centres are important in many biological processes. In natural systems, metallotetrapyrrole units carry respiratory gases or provide sensing and catalytic functions. Conceiving synthetic model systems strongly helps to determine the pertinent chemical foundations for such processes, with recent work highlighting the importance of the prosthetic groups' conformational flexibility as an intricate variable affecting their functional properties. Here, we present simple model systems to investigate, at the single molecule level, the interaction of carbon monoxide with saddle-shaped iron- and cobalt-porphyrin conformers, which have been stabilized as two-dimensional arrays on well-defined surfaces. Using scanning tunnelling microscopy we identified a novel bonding scheme expressed in tilted monocarbonyl and cis-dicarbonyl configurations at the functional metal-macrocycle unit. Modelling with density functional theory revealed that the weakly bonded diatomic carbonyl adduct can effectively bridge specific pyrrole groups with the metal atom as a result of the pronounced saddle-shape conformation of the porphyrin cage.

  1. O2 and CO binding to tetraaza-tripodal-capped iron(II) porphyrins.

    PubMed

    Ruzié, Christian; Even, Pascale; Ricard, David; Roisnel, Thierry; Boitrel, Bernard

    2006-02-06

    A series of tris(2-aminoethylamine) (tren) capped iron(II) porphyrins has been synthesized and characterized and their affinities for dioxygen and carbon monoxide measured. The X-ray structure of the basic scaffold with nickel inserted in the porphyrin is also reported. All the ligands differ by the nature of the group(s) attached to the secondary amine functions of the cap. These various substitutions were introduced to probe if a hydrogen bond with these secondary amine groups acting as the donor could rationalize the high affinity of these myoglobin models. This work clearly indicates that the cage structure of the tren predominates over all the other appended groups with the exception of p-nitrophenol.

  2. Water-soluble Manganese and Iron Mesotetrakis(carboxyl)porphyrin: DNA Binding, Oxidative Cleavage, and Cytotoxic Activities.

    PubMed

    Shi, Lei; Jiang, Yi-Yu; Jiang, Tao; Yin, Wei; Yang, Jian-Ping; Cao, Man-Li; Fang, Yu-Qi; Liu, Hai-Yang

    2017-06-29

    Two new water-soluble metal carboxyl porphyrins, manganese (III) meso -tetrakis (carboxyl) porphyrin and iron (III) meso -tetrakis (carboxyl) porphyrin, were synthesized and characterized. Their interactions with ct-DNA were investigated by UV-Vis titration, fluorescence spectra, viscosity measurement and CD spectra. The results showed they can strongly bind to ct-DNA via outside binding mode. Electrophoresis experiments revealed that both complexes can cleave pBR322 DNA efficiently in the presence of hydrogen peroxide, albeit 2-Mn exhibited a little higher efficiency. The inhibitor tests suggest the oxidative DNA cleavage by these two complexes may involve hydroxyl radical active intermediates. Notably, 2-Mn exhibited considerable photocytotoxicity against Hep G2 cell via triggering a significant generation of ROS and causing disruption of MMP after irradiation.

  3. Electron Transport through Porphyrin Molecular Junctions

    NASA Astrophysics Data System (ADS)

    Zhou, Qi

    The goal of this work is to study the properties that would affect the electron transport through a porphyrin molecular junction. This work contributes to the field of electron transport in molecular junctions in the following 3 aspects. First of all, by carrying out experiments comparing the conductance of the iron (III) porphyrin (protected) and the free base porphyrin (protected), it is confirmed that the molecular energy level broadening and shifting occurs for porphyrin molecules when coupled with the metal electrodes, and this level broadening and shifting plays an important role in the electron transport through molecular junctions. Secondly, by carrying out an in-situ deprotection of the acetyl-protected free base porphyrin molecules, it is found out that the presence of acetyl groups reduces the conductance. Thirdly, by incorporating the Matrix-assisted laser desorption/ionization (MALDI) spectrum and the in-situ deprotection prior to formation of molecular junctions, it allows a more precise understanding of the molecules involved in the formation of molecular junctions, and therefore allows an accurate analysis of the conductance histogram. The molecules are prepared by self-assembly and the junctions are formed using a Scanning Tunneling Microscopy (STM) molecular break junction technique. The porphyrin molecules are characterized by MALDI in solution before self-assembly to a gold/mica substrate. The self-assembled monolayers (SAMs) of porphyrins on gold are characterized by Ultraviolet-visible (UV-Vis) reflection spectroscopy to confirm that the molecules are attached to the substrate. The SAMs are then characterized by Angle-Resolved X-ray photoelectron spectroscopy (ARXPS) to determine the thickness and the average molecular orientation of the molecular layer. The electron transport is measured by conductance-displacement (G-S) experiments under a given bias (-0.4V). The conductance value of a single molecule is identified by a statistical analysis

  4. Iron-catalyzed halogenation of alkanes: modeling of nonheme halogenases by experiment and DFT calculations.

    PubMed

    Comba, Peter; Wunderlich, Steffen

    2010-06-25

    When the dichloroiron(II) complex of the tetradentate bispidine ligand L=3,7-dimethyl-9-oxo-2,4-bis(2-pyridyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate methyl ester is oxidized with H(2)O(2), tBuOOH, or iodosylbenzene, the high-valent Fe=O complex efficiently oxidizes and halogenates cyclohexane. Kinetic D isotope effects and the preference for the abstraction of tertiary over secondary carbon-bound hydrogen atoms (quantified in the halogenation of adamantane) indicate that C-H activation is the rate-determining step. The efficiencies (yields in stoichiometric and turnover numbers in catalytic reactions), product ratios (alcohol vs. bromo- vs. chloroalkane), and kinetic isotope effects depend on the oxidant. These results suggest different pathways with different oxidants, and these may include iron(IV)- and iron(V)-oxo complexes as well as oxygen-based radicals.

  5. Nuclear Resonance Vibrational Spectra of Five-Coordinate Imidazole-ligated Iron(II) Porphyrinates

    PubMed Central

    Hu, Chuanjiang; Barabanschikov, Alexander; Ellison, Mary K.; Zhao, Jiyong; Alp, E. Ercan; Sturhahn, Wolfgang; Zgierski, Marek Z.; Sage, J. Timothy; Scheidt, W. Robert

    2012-01-01

    Nuclear resonance vibrational spectra have been obtained for six five-coordinate imidazole-ligated iron(II) porphyrinates, [Fe(Por)(L)] (Por = tetraphenylporphyrinate, octaethylporphyrinate, tetratolylporphyrinate or protoporphyrinate IX and L = 2-methylimidazole or 1,2-dimethylimidazole). Measurements have been made on both powder and oriented crystal samples. The spectra are dominated by strong signals around 200–300 cm−1. Although the in-plane and out-of-plane vibrations are seriously overlapped, oriented crystal spectra allow their deconvolution. Thus, oriented crystal experimental data, along with DFT calculations, enable the assignment of key vibrations in the spectra. Molecular dynamics are also discussed. The nature of the Fe–NIm vibrations has been elaborated further than was possible from resonance Raman studies. Our study suggests that the Fe motions are coupled with the porphyrin core and peripheral groups motions. Both peripheral groups and their conformations have significant influence on the vibrational spectra (position and shape). PMID:22243131

  6. Iron porphyrinate Fe(TPPS) reduces brain cell damage in rats intrastriatally lesioned by quinolinate.

    PubMed

    González-Cortés, Carolina; Salinas-Lara, Citlaltepetl; Gómez-López, Marcos Artemio; Tena-Suck, Martha Lilia; Pérez-De La Cruz, Verónica; Rembao-Bojórquez, Daniel; Pedraza-Chaverrí, José; Gómez-Ruiz, Celedonio; Galván-Arzate, Sonia; Ali, Syed F; Santamaría, Abel

    2008-01-01

    It has been recently demonstrated that the reactive nitrogen species (RNS) peroxynitrite (ONOO(-)) is involved in the neurotoxic pattern produced by quinolinic acid in the rat brain [V. Pérez-De La Cruz, C. González-Cortés, S. Galván-Arzate, O.N. Medina-Campos, F. Pérez-Severiano, S.F. Ali, J. Pedraza-Chaverrí, A. Santamaría, Excitotoxic brain damage involves early peroxynitrite formation in a model of Huntington's disease in rats: protective role of iron porphyrinate 5,10,15,20-tetrakis (4-sulfonatophenyl)porphyrinate iron (III), Neuroscience 135 (2005) 463-474.]. The aim of this work was to investigate whether ONOO(-) can also be responsible for morphological alterations and inflammatory events in the same paradigm. For this purpose, we evaluated the effect of a pre-treatment with the iron porphyrinate Fe(TPPS), a well-known ONOO(-) decomposition catalyst (10 mg/kg, i.p., 120 min before lesion), on the quinolinate-induced striatal cell damage and immunoreactivities to glial-fibrilar acidic protein (GFAP), interleukin 6 (IL-6) and inducible nitric oxide synthase (iNOS), one and seven days after the intrastriatal infusion of quinolinate (240 nmol/microl) to rats. The striatal tissue from animals lesioned by quinolinate showed a significant degree of damage and enhanced immunoreactivities to GFAP, IL-6 and iNOS, both at 1 and 7 days post-lesion. Pre-treatment of rats with Fe(TPPS) significantly attenuated or prevented all these markers at both post-lesion times tested, except for GFAP immunoreactivity at 7 days post-lesion and iNOS immunoreactivity at 1 day post-lesion. Altogether, our results suggest that ONOO(-) is actively participating in triggering inflammatory events and morphological alterations in the toxic model produced by quinolinate, since the use of agents affecting its formation, such as Fe(TPPS), are effective experimental tools to reduce the brain lesions associated to excitotoxic and oxidative damage.

  7. Haloporphyrins and their preparation and use as catalysts

    DOEpatents

    Ellis, Jr., Paul E.; Lyons, James E.

    1997-01-01

    The invention provides novel catalyst compositions, useful in the oxidation of hydrocarbons with air or oxygen to form hydroxy-group containing compounds and in the decomposition of hydroperoxides to form hydroxy-group containing compounds. The catalysts comprise transition metal complexes of a porphyrin ring having 1 to 12 halogen substituents on the porphyrin ring, at least one of said halogens being in a meso position and/or the catalyst containing no aryl group in a meso position. The compositions are prepared by halogenating a transition metal complex of a porphyrin. In one embodiment, a complex of a porphyrin with a metal whose porphyrin complexes are not active for oxidation of hydrocarbons is halogenated, thereby to obtain a haloporphyrin complex of that metal, the metal is removed from the haloporphyrin complex to obtain the free base form of the haloporphyrin, and a metal such as iron whose porphyrin complexes are active for oxidation of hydrocarbons and for the decomposition of alkyl hydroperoxides is complexed with the free base to obtain an active catalyst for oxidation of hydrocarbons and decomposition of alkyl hydroperoxides.

  8. Haloporphyrins and their preparation and use as catalysts

    DOEpatents

    Ellis, P.E. Jr.; Lyons, J.E.

    1997-09-02

    The invention provides novel catalyst compositions, useful in the oxidation of hydrocarbons with air or oxygen to form hydroxy-group containing compounds and in the decomposition of hydroperoxides to form hydroxy-group containing compounds. The catalysts comprise transition metal complexes of a porphyrin ring having 1 to 12 halogen substituents on the porphyrin ring, at least one of said halogens being in a meso position and/or the catalyst containing no aryl group in a meso position. The compositions are prepared by halogenating a transition metal complex of a porphyrin. In one embodiment, a complex of a porphyrin with a metal whose porphyrin complexes are not active for oxidation of hydrocarbons is halogenated, thereby to obtain a haloporphyrin complex of that metal, the metal is removed from the haloporphyrin complex to obtain the free base form of the haloporphyrin, and a metal such as iron whose porphyrin complexes are active for oxidation of hydrocarbons and for the decomposition of alkyl hydroperoxides is complexed with the free base to obtain an active catalyst for oxidation of hydrocarbons and decomposition of alkyl hydroperoxides.

  9. Effect of halogenation on the nonlinear optical properties of porthyrin and substituted porphyrins

    NASA Technical Reports Server (NTRS)

    Cardelino, Beatriz H.; Moore, Craig E.; Benloss, Angela; Thompson, Albert N., Jr.; Richards, Rosalie A.; Roney, Celeste A.; Sanghadasa, Mohan

    1998-01-01

    The effect that fluorine and chlorine substitution has on the nonlinear optical properties of porphyrin, tetramethylporphyrin and tetraphenylporphyrin has been theoretically studied. The calculations of nonlinear optical properties have been obtained by performing finite-field calculations on structures determined by semiempirical methods. In addition, tetra(p-chlorophenyl)porphyrin and tetra(p-bromophenyl)porphyrin were synthesized by the condensation of pyrrol and the appropriate aldehyde. Thin films of polymethylmethacrylate were obtained containing these materials, by spin coating onto glass substrates. The films were characterized by third-harmonic generation. It was determined that the experimental conditions enhance the third-order polarizability of the tetraphenylporphyrins by a factor of about 1.6.

  10. A Base-Resistant Metalloporphyrin Metal–Organic Framework for C–H Bond Halogenation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lv, Xiu-Liang; Wang, Kecheng; Wang, Bin

    A base-resistant porphyrin metal–organic framework (MOF), namely PCN-602 has been constructed with 12-connected [Ni 8(OH) 4(H 2O) 2Pz 12] (Pz = pyrazolate) cluster and a newly designed pyrazolate-based porphyrin ligand, 5,10,15,20-tetrakis(4-(pyrazolate-4-yl)phenyl)porphyrin under the guidance of the reticular synthesis strategy. Besides its robustness in hydroxide solution, PCN-602 also shows excellent stability in aqueous solutions of F –, CO 3 2–, and PO 4 3– ions. Interestingly, the Mn 3+-porphyrinic PCN-602, as a recyclable MOF catalyst, presents high catalytic activity for the C–H bond halogenation reaction in a basic system, significantly outperforming its homogeneous counterpart. For the first time, a porphyrinic MOFmore » was thus used as an efficient catalyst in a basic solution with coordinating anions, to the best of our knowledge.« less

  11. Reactions catalyzed by haloporphyrins

    DOEpatents

    Ellis, P.E. Jr.; Lyons, J.E.

    1996-02-06

    The invention provides novel methods for the oxidation of hydrocarbons with oxygen-containing gas to form hydroxy-group containing compounds and for the decomposition of hydroperoxides to form hydroxy-group containing compounds. The catalysts used in the methods of the invention comprise transition metal complexes of a porphyrin ring having 1 to 12 halogen substituents on the porphyrin ring, at least one of said halogens being in a meso position and/or the catalyst containing no aryl group in a meso position. The catalyst compositions are prepared by halogenating a transition metal complex of a porphyrin. In one embodiment, a complex of a porphyrin with a metal whose porphyrin complexes are not active for oxidation of alkanes is halogenated, thereby to obtain a haloporphyrin complex of that metal, the metal is removed from the haloporphyrin complex to obtain the free base form of the haloporphyrin, and a metal such as iron whose porphyrin complexes are active for oxidation of alkanes and for the decomposition of alkyl hydroperoxides is complexed with the free base to obtain an active catalyst for oxidation of alkanes and decomposition of alkyl hydroperoxides.

  12. Reactions catalyzed by haloporphyrins

    DOEpatents

    Ellis, Jr., Paul E.; Lyons, James E.

    1996-01-01

    The invention provides novel methods for the oxidation of hydrocarbons with oxygen-containing gas to form hydroxy-group containing compounds and for the decomposition of hydroperoxides to form hydroxygroup containing compounds. The catalysts used in the methods of the invention comprise transition metal complexes of a porphyrin ring having 1 to 12 halogen substituents on the porphyrin ring, at least one of said halogens being in a meso position and/or the catalyst containing no aryl group in a meso position. The catalyst compositions are prepared by halogenating a transition metal complex of a porphyrin. In one embodiment, a complex of a porphyrin with a metal whose porphyrin complexes are not active for oxidation of alkanes is halogenated, thereby to obtain a haloporphyrin complex of that metal, the metal is removed from the haloporphyrin complex to obtain the free base form of the haloporphyrin, and a metal such as iron whose porphyrin complexes are active for oxidation of alkanes and for the decomposition of alkyl hydroperoxides is complexed with the free base to obtain an active catalyst for oxidation of alkanes and decomposition of alkyl hydroperoxides.

  13. Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation

    DOEpatents

    Ellis, P.E. Jr.; Lyons, J.E.

    1995-01-17

    New compositions of matter comprising cyano-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has cyano groups attached thereto in meso and/or [beta]-pyrrolic positions.

  14. Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation

    DOEpatents

    Ellis, P.E. Jr.; Lyons, J.E.

    1993-05-18

    New compositions of matter comprising cyano-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has cyano groups attached thereto in meso- and/or [beta]-pyrrolic positions.

  15. Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation

    DOEpatents

    Ellis, Jr., Paul E.; Lyons, James E.

    1993-01-01

    New compositions of matter comprising cyano-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has cyano groups attached thereto in meso and/or .beta.-pyrrolic positions.

  16. Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation

    DOEpatents

    Ellis, Jr., Paul E.; Lyons, James E.

    1995-01-01

    New compositions of matter comprising cyano-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has cyano groups attached thereto in meso and/or .beta.-pyrrolic positions.

  17. Evidence that a formyl-substituted iron porphyrin is the prosthetic group of myeloperoxidase: magnetic circular dichroism similarity of the peroxidase to Spirographis heme-reconstituted myoglobin.

    PubMed Central

    Sono, M; Bracete, A M; Huff, A M; Ikeda-Saito, M; Dawson, J H

    1991-01-01

    To probe the identity of the active site heme-type prosthetic group of myeloperoxidase, whose structure has not been established unambiguously [proposed structures are (i) a chlorin (dihydroporphyrin) or (ii) a formyl-substituted porphyrin such as present in heme a], Spirographis heme (2-formyl-4-vinyldeuteroheme IX) has been incorporated into apo-myoglobin as a possible iron porphyrin model. Comparison of parallel derivatives of these two green proteins with magnetic circular dichroism spectroscopy reveals considerable similarities between several derivatives of these proteins, including the pyridine hemochromogen, the native ferric, ferrous-oxy, and ferrous-CO forms. In contrast, the magnetic circular dichroism spectra of available iron chlorin (octaethylchlorin) model complexes in analogous ligation and oxidation states do not show any significant spectral similarities to myeloperoxidase. This finding provides important evidence in favor of a formyl-substituted porphyrin as the structure of the prosthetic group macrocycle of myeloperoxidase. PMID:1662385

  18. Independent Evolution of Six Families of Halogenating Enzymes.

    PubMed

    Xu, Gangming; Wang, Bin-Gui

    2016-01-01

    Halogenated natural products are widespread in the environment, and the halogen atoms are typically vital to their bioactivities. Thus far, six families of halogenating enzymes have been identified: cofactor-free haloperoxidases (HPO), vanadium-dependent haloperoxidases (V-HPO), heme iron-dependent haloperoxidases (HI-HPO), non-heme iron-dependent halogenases (NI-HG), flavin-dependent halogenases (F-HG), and S-adenosyl-L-methionine (SAM)-dependent halogenases (S-HG). However, these halogenating enzymes with similar biological functions but distinct structures might have evolved independently. Phylogenetic and structural analyses suggest that the HPO, V-HPO, HI-HPO, NI-HG, F-HG, and S-HG enzyme families may have evolutionary relationships to the α/β hydrolases, acid phosphatases, peroxidases, chemotaxis phosphatases, oxidoreductases, and SAM hydroxide adenosyltransferases, respectively. These halogenating enzymes have established sequence homology, structural conservation, and mechanistic features within each family. Understanding the distinct evolutionary history of these halogenating enzymes will provide further insights into the study of their catalytic mechanisms and halogenation specificity.

  19. Independent Evolution of Six Families of Halogenating Enzymes

    PubMed Central

    Xu, Gangming; Wang, Bin-Gui

    2016-01-01

    Halogenated natural products are widespread in the environment, and the halogen atoms are typically vital to their bioactivities. Thus far, six families of halogenating enzymes have been identified: cofactor-free haloperoxidases (HPO), vanadium-dependent haloperoxidases (V-HPO), heme iron-dependent haloperoxidases (HI-HPO), non-heme iron-dependent halogenases (NI-HG), flavin-dependent halogenases (F-HG), and S-adenosyl-L-methionine (SAM)-dependent halogenases (S-HG). However, these halogenating enzymes with similar biological functions but distinct structures might have evolved independently. Phylogenetic and structural analyses suggest that the HPO, V-HPO, HI-HPO, NI-HG, F-HG, and S-HG enzyme families may have evolutionary relationships to the α/β hydrolases, acid phosphatases, peroxidases, chemotaxis phosphatases, oxidoreductases, and SAM hydroxide adenosyltransferases, respectively. These halogenating enzymes have established sequence homology, structural conservation, and mechanistic features within each family. Understanding the distinct evolutionary history of these halogenating enzymes will provide further insights into the study of their catalytic mechanisms and halogenation specificity. PMID:27153321

  20. Syntheses and Functionalizations of Porphyrin Macrocycles

    PubMed Central

    Vicente, Maria da G.H.; Smith, Kevin M.

    2014-01-01

    Porphyrin macrocycles have been the subject of intense study in the last century because they are widely distributed in nature, usually as metal complexes of either iron or magnesium. As such, they serve as the prosthetic groups in a wide variety of primary metabolites, such as hemoglobins, myoglobins, cytochromes, catalases, peroxidases, chlorophylls, and bacteriochlorophylls; these compounds have multiple applications in materials science, biology and medicine. This article describes current methodology for preparation of simple, symmetrical model porphyrins, as well as more complex protocols for preparation of unsymmetrically substituted porphyrin macrocycles similar to those found in nature. The basic chemical reactivity of porphyrins and metalloporphyrin is also described, including electrophilic and nucleophilic reactions, oxidations, reductions, and metal-mediated cross-coupling reactions. Using the synthetic approaches and reactivity profiles presented, eventually almost any substituted porphyrin system can be prepared for applications in a variety of areas, including in catalysis, electron transport, model biological systems and therapeutics. PMID:25484638

  1. Reactivity of substituted benzotrichlorides toward granular iron, Cr(II), and an iron(II) porphyrin: A correlation analysis.

    PubMed

    Kohn, Tamar; Arnold, William A; Roberts, A Lynn

    2006-07-01

    Cross-correlations of rate constants between a system of interest and a better-defined one have become popular as a tool in studying transformations of organic pollutants. A slope of unity (if the correlation is conducted on a log-log basis) in such plots has been invoked as evidence of a common mechanism. To explore this notion, benzotrichloride and several of its substituted analogues were reacted with Cr(H2O)6(2+), an iron(II) porphyrin (iron meso-tetra(4-carboxyphenyl)porphine chloride, Fe(II)TCP), and granular iron. The first two reductants react with organohalides by dissociative inner sphere single-electron transfer, while mechanism(s) for organohalide reduction by granular iron are still debated. Apartfrom sterically hindered compounds, good correlations were obtained in comparing any two systems, although slopes (on a log-log basis) deviated from unity. We argue that a slope of unity is neither necessary nor sufficient evidence of a common mechanism. Overall rate constants may be composite entities, consisting in part of rate or equilibrium constants for adsorption onto surfaces or for precursor formation in solution; these components may differ between systems in their susceptibility to substituent effects. Cross-correlations may prove useful in predicting reactivity in the absence of steric effects, but additional evidence is required in deducing reaction mechanisms.

  2. Novel spin transition between S = 5/2 and S = 3/2 in highly saddled iron(III) porphyrin complexes at extremely low temperatures.

    PubMed

    Ohgo, Yoshiki; Chiba, Yuya; Hashizume, Daisuke; Uekusa, Hidehiro; Ozeki, Tomoji; Nakamura, Mikio

    2006-05-14

    A novel spin transition between S = 5/2 and S = 3/2 has been observed for the first time in five-coordinate, highly saddled iron(III) porphyrinates by EPR and SQUID measurements at extremely low temperatures.

  3. Iron porphyrin-modified PVDF membrane as a biomimetic material and its effectiveness on nitric oxide binding

    NASA Astrophysics Data System (ADS)

    Can, Faruk; Demirci, Osman Cahit; Dumoulin, Fabienne; Erhan, Elif; Arslan, Leyla Colakerol; Ergenekon, Pınar

    2017-10-01

    Nitric oxide (NO) is a reactive gas well-known as an air pollutant causing severe environmental problems. NO is also an important signaling molecule having a strong affinity towards heme proteins in the body. Taking this specialty as a model, a biomimetic membrane was developed by modification of the membrane surface with iron-porphyrin which depicts very similar structure to heme proteins. In this study, PVDF membrane was coated with synthesized (4-carboxyphenyl)-10,15,20-triphenyl-porphyrin iron(III) chloride (FeCTPP) to promote NO fixation on the surface. The coated membrane was characterized in terms of ATR-IR spectra, contact angle measurement, chemical composition, and morphological structure. Contact angle of original PVDF first decreased sharply after plasma treatment and surface polymerization steps but after incorporation of FeCTPP, the surface acquired its hydrophobicity again. NO binding capability of modified membrane surface was evaluated on the basis of X-ray Photoelectron. Upon exposure to NO gas, a chemical shift of Fe+3 and appearance of new N peak was observed due to the electron transfer from NO ligand to Fe ion with the attachment of nitrosyl group to FeCTPP. This modification brings the functionality to the membrane for being used in biological systems such as membrane bioreactor material in biological NO removal technology.

  4. Solution behavior of iron(III) and iron(II) porphyrins in DMSO and reaction with superoxide. Effect of neighboring positive charge on thermodynamics, kinetics and nature of iron-(su)peroxo product.

    PubMed

    Duerr, K; Troeppner, O; Olah, J; Li, J; Zahl, A; Drewello, T; Jux, N; Harvey, J N; Ivanović-Burmazović, I

    2012-01-14

    The solution behavior of iron(III) and iron(II) complexes of 5(4),10(4),15(4),20(4)-tetra-tert-butyl-5,10,15,20-tetraphenylporphyrin (H(2)tBuTPP) and the reaction with superoxide (KO(2)) in DMSO have been studied in detail. Applying temperature and pressure dependent NMR studies, the thermodynamics of the low-spin/high-spin equilibrium between bis- and mono-DMSO Fe(II) forms have been quantified (K(DMSO) = 0.082 ± 0.002 at 298.2 K, ΔH° = +36 ± 1 kJ mol(-1), ΔS° = +101 ± 4 J K(-1) mol(-1), ΔV° = +16 ± 2 cm(3) mol(-1)). This is a key activation step for substitution and inner-sphere electron transfer. The superoxide binding constant to the iron(II) form of the studied porphyrin complex was found to be (9 ± 0.5) × 10(3) M(-1), and does not change significantly in the presence of the externally added crown ether in DMSO (11 ± 4) × 10(3) M(-1). The rate constants for the superoxide binding (k(on) = (1.30 ± 0.01) × 10(5) M(-1) s(-1)) and release (k(off) = 11.6 ± 0.7 s(-1)) are not affected by the presence of the external crown ether in solution. The resulting iron(II)-superoxide adduct has been characterized (mass spectrometry, EPR, high-pressure UV/Vis spectroscopy) and upon controlled addition of a proton source it regenerates the starting iron(II) complex. Based on DFT calculations, the reaction product without neighboring positive charge has iron(II)-superoxo character in both high-spin side-on and low-spin end-on forms. The results are compared to those obtained for the analogous complex with covalently attached crown ether, and more general conclusions regarding the spin-state equilibrium of iron(II) porphyrins, their reaction with superoxide and the electronic structure of the product species are drawn.

  5. A novel sensor for monitoring of iron(III) ions based on porphyrins.

    PubMed

    Vlascici, Dana; Fagadar-Cosma, Eugenia; Popa, Iuliana; Chiriac, Vlad; Gil-Agusti, Mayte

    2012-01-01

    Three A(3)B porphyrins with mixed carboxy-, phenoxy-, pyridyl-, and dimethoxy-substituent functionalization on the meso-phenyl groups were obtained by multicomponent synthesis, fully characterized and used as ionophores for preparing PVC-based membrane sensors selective to iron(III). The membranes have an ionophore:PVC:plasticizer composition ratio of 1:33:66. Sodium tetraphenylborate was used as additive (20 mol% relative to ionophore). The performance characteristics (linear concentration range, slope and selectivity) of the sensors were investigated. The best results were obtained for the membrane based on 5-(4-carboxyphenyl)-10,15,20-tris(4-phenoxyphenyl)-porphyrin plasticized with bis(2-ethylhexyl)sebacate, in a linear range from 1 × 10(-7)-1 × 10(-1) M with a slope of 21.6 mV/decade. The electrode showed high selectivity with respect to alkaline and heavy metal ions and a response time of 20 s. The influence of pH on the sensor response was studied. The sensor was used for a period of six weeks and the utility has been tested for the quantitative determination of Fe(III) in recovered solutions from spent lithium ion batteries and for the quantitative determination of Fe(III) in tap water samples.

  6. A Novel Sensor for Monitoring of Iron(III) Ions Based on Porphyrins

    PubMed Central

    Vlascici, Dana; Fagadar-Cosma, Eugenia; Popa, Iuliana; Chiriac, Vlad; Gil-Agusti, Mayte

    2012-01-01

    Three A3B porphyrins with mixed carboxy-, phenoxy-, pyridyl-, and dimethoxy-substituent functionalization on the meso-phenyl groups were obtained by multicomponent synthesis, fully characterized and used as ionophores for preparing PVC-based membrane sensors selective to iron(III). The membranes have an ionophore:PVC:plasticizer composition ratio of 1:33:66. Sodium tetraphenylborate was used as additive (20 mol% relative to ionophore). The performance characteristics (linear concentration range, slope and selectivity) of the sensors were investigated. The best results were obtained for the membrane based on 5-(4-carboxyphenyl)-10,15,20-tris(4-phenoxyphenyl)-porphyrin plasticized with bis(2-ethylhexyl)sebacate, in a linear range from 1 × 10−7–1 × 10−1 M with a slope of 21.6 mV/decade. The electrode showed high selectivity with respect to alkaline and heavy metal ions and a response time of 20 s. The influence of pH on the sensor response was studied. The sensor was used for a period of six weeks and the utility has been tested for the quantitative determination of Fe(III) in recovered solutions from spent lithium ion batteries and for the quantitative determination of Fe(III) in tap water samples. PMID:22969395

  7. Emulating porphyrins with a rippled multivacancy graphene system

    NASA Astrophysics Data System (ADS)

    Mombrú, Dominique; Faccio, Ricardo; Mombrú, Alvaro W.

    2018-04-01

    The interaction between a complex porphyrin-like system formed by an iron atom and multivacant graphene layer and O2, CO and CO2 molecules is studied, using Density Functional Theory (DFT) calculations. The multivacancy graphene system used for this study, consists in the removal of a 1,4-dimethybenzene-like moiety, in a 6 × 6 supercell. This removal and the structural optimization subsequently performed, yield to a biaxial vacancy, where the location of an iron atom embedded in it, lead to a system with resemblance to iron-porphyrin systems. This similar structure could be used to form complexes where gas molecules are allowed to interact with these iron-octavacant graphene systems. The study focuses on the structure of the system and the net magnetic moment for different gas molecules: O2, CO2 and CO. Rippling in the vacant graphene is enhanced through this interaction.

  8. Comparison of the oxidation products produced by tetrahalobisphenol A flame retardants as a result of potassium monopersulfate oxidation with an iron(III)-tetrakis(p-sulfonatophenyl)porphyrin in the presence of humic acid.

    PubMed

    Mizutani, Yusuke; Maeno, Shohei; Zhu, Qianqian; Fukushima, Masami

    2014-01-01

    Tetrabromobisphenol A (TBBPA) and tetrachlorobisphenol A (TCBPA), commercially used halogenated flame retardants, can be found in leachates from landfills, because hydrophobic interactions with humic acids (HAs), major organic components in landfills, result in an increase in their solubility. The oxidation characteristics of TBBPA and TCBPA in the presence of HA were compared using a catalytic system comprised of a combination of iron(III)-tetrakis(p-sulfophenyl)porphyrin (FeTPPS) and KHSO5 that can mimic the enzymatic reactions that occur in landfills. The levels of degradation and dehalogenation of TBBPA and TCBPA at pH 4 were significantly lower than at pH 8, which is a typical pH value for landfill leachates. In the presence of HA at pH 8, 2-hydroxyisopropyl-2,6 -dihalophenols (2HIP-26DXPs) were detected as major by-products. These compounds are likely produced via the β-carbon scission of the substrates, and their levels decreased with increasing reaction time. The levels of coupling compounds between 2,6-dihalopnenols and TBBPA or TCBPA increased with reaction time. The 27% of Br in the degraded TBBPA and 50% of Cl in the degraded TCBPA were incorporated into the HA as a result of catalytic oxidation via the FeTPPS/KHSO5 system. These results suggest that TCBPA is incorporated into HA more readily than TBBPA. The coupling compounds between HA and halogenated intermediates from TBBPA or TCBPA were assigned by pyrolysis-gas chromatography/mass spectrometry.

  9. Effects of Imidazole Deprotonation on Vibrational Spectra of High-Spin Iron(II) Porphyrinates

    PubMed Central

    Hu, Chuanjiang; Peng, Qian; Silvernail, Nathan J.; Barabanschikov, Alexander; Zhao, Jiyong; Alp, E. Ercan; Sturhahn, Wolfgang; Sage, J. Timothy; Scheidt, W. Robert

    2013-01-01

    The effects of the deprotonation of coordinated imidazole on the dynamics of five-coordinate high-spin iron(II) porphyrinates have been investigated using nuclear resonance vibrational spectroscopy. Two complexes have been studied in detail with both powder and oriented single-crystal measurements. Changes in the vibrational spectra are clearly related to structural differences in the molecular structures that occur when imidazole is deprotonated. Most modes involving the simultaneous motion of iron and imidazolate are unresolved but the one mode that is resolved is found at higher frequency in the imidazolates. These out-of-plane results are in accord with earlier resonance Raman studies of heme proteins. We also show the imidazole vs. imidazolate differences in the in-plane vibrations that are not accessible to resonance Raman studies. The in-plane vibrations are at lower frequency in the imidazolate derivatives; the doming mode shifts are inconclusive. The stiffness, an experimentally determined force constant that averages the vibrational details to quantify the nearest-neighbor interactions, confirms that deprotonation inverts the relative strengths of axial and equatorial coordination. PMID:23470205

  10. Ferryl Protonation in Oxoiron(IV) Porphyrins and Its Role in Oxygen Transfer

    DOE PAGES

    Boaz, Nicholas C.; Bell, Seth R.; Groves, John T.

    2015-02-04

    Ferryl porphyrins, P–Fe IVmore » $=$O, are central reactive intermediates in the catalytic cycles of numerous heme proteins and a variety of model systems. There has been considerable interest in elucidating factors, such as terminal oxo basicity, that may control ferryl reactivity. Here in this study, the sulfonated, water-soluble ferryl porphyrin complexes tetramesitylporphyrin, oxoFe IVTMPS (FeTMPS-II), its 2,6-dichlorophenyl analogue, oxoFe IVTDClPS (FeTDClPS-II), and two other analogues are shown to be protonated under turnover conditions to produce the corresponding bis-aqua-iron(III) porphyrin cation radicals. The results reveal a novel internal electromeric equilibrium, P–Fe IV$=$O $$\\leftrightarrows$$ P +–Fe III(OH 2) 2. Reversible pKa values in the range of 4–6.3 have been measured for this process by pH-jump, UV–vis spectroscopy. Ferryl protonation has important ramifications for C–H bond cleavage reactions mediated by oxoiron(IV) porphyrin cation radicals in protic media. Both solvent O–H and substrate C–H deuterium kinetic isotope effects are observed for these reactions, indicating that hydrocarbon oxidation by these oxoiron(IV) porphyrin cation radicals occurs via a solvent proton-coupled hydrogen atom transfer from the substrate that has not been previously described. The effective FeO–H bond dissociation energies for FeTMPS-II and FeTDClPS-II were estimated from similar kinetic reactivities of the corresponding oxoFe IVTMPS + and oxoFe IVTDClPS + species to be ~92–94 kcal/mol. Similar values were calculated from the two-proton P +–Fe III(OH 2) 2 pK a obs and the porphyrin oxidation potentials, despite a 230 mV range for the iron porphyrins examined. Thus, the iron porphyrin with the lower ring oxidation potential has a compensating higher basicity of the ferryl oxygen. The solvent-derived proton adds significantly to the driving force for C–H bond scission.« less

  11. Iron L-edge X-ray Absorption Spectroscopy of Oxy-Picket Fence Porphyrin: Experimental Insight into Fe-O2 Bonding

    PubMed Central

    Wilson, Samuel A.; Kroll, Thomas; Decreau, Richard A.; Hocking, Rosalie K.; Lundberg, Marcus; Hedman, Britt; Hodgson, Keith O.; Solomon, Edward I.

    2013-01-01

    The electronic structure of the Fe–O2 center in oxy-hemoglobin and oxy-myoglobin is a long-standing issue in the field of bioinorganic chemistry. Spectroscopic studies have been complicated by the highly delocalized nature of the porphyrin and calculations require interpretation of multi-determinant wavefunctions for a highly covalent metal site. Here, iron L-edge X-ray absorption spectroscopy (XAS), interpreted using a valence bond configuration interaction (VBCI) multiplet model, is applied to directly probe the electronic structure of the iron in the biomimetic Fe–O2 heme complex [Fe(pfp)(1-MeIm)O2] (pfp = meso-tetra(α,α,α,α-o-pivalamidophenyl) porphyrin or TpivPP). This method allows separate estimates of σ-donor, π-donor, and π-acceptor interactions through ligand to metal charge transfer (LMCT) and metal to ligand charge transfer (MLCT) mixing pathways. The L-edge spectrum of [Fe(pfp)(1-MeIm)O2] is further compared to those of [FeII(pfp)(1-MeIm)2], [FeII(pfp)], and [FeIII(tpp)(ImH)2]Cl (tpp = meso-tetraphenylporphyrin) which have FeII S = 0, FeII S = 1 and FeIII S = 1/2 ground states, respectively. These serve as references for the three possible contributions to the ground state of oxy-pfp. The Fe–O2 pfp site is experimentally determined to have both significant σ-donation and a strong π-interaction of the O2 with the iron, with the latter having implications with respect to the spin polarization of the ground state. PMID:23259487

  12. Electrically conducting porphyrin and porphyrin-fullerene electropolymers

    DOEpatents

    Gust, Jr., John Devens; Liddell, Paul Anthony; Gervaldo, Miguel Andres; Bridgewater, James Ward; Brennan, Bradley James; Moore, Thomas Andrew; Moore, Ana Lorenzelli

    2014-03-11

    Compounds with aryl ring(s) at porphyrin meso position(s) bearing an amino group in position 4 relative to the porphyrin macrocycle, and at least one unsubstituted 5 (hydrogen-bearing) meso position with the 10-, 15-, and/or 20-relationship to the aryl ring bearing the amino group, and metal complexes thereof, feature broad spectral absorption throughout the visible region. These compounds are electropolymerized to form electrically conducting porphyrin and porphyrin-fullerene polymers that are useful in photovoltaic applications. The structure of one such electrically conducting porphyrin polymer is shown below. ##STR00001##

  13. Using porphyrin-amino acid pairs to model the electrochemistry of heme proteins: experimental and theoretical investigations.

    PubMed

    Samajdar, Rudra N; Manogaran, Dhivya; Yashonath, S; Bhattacharyya, Aninda J

    2018-04-18

    Quasi reversibility in electrochemical cycling between different oxidation states of iron is an often seen characteristic of iron containing heme proteins that bind dioxygen. Surprisingly, the system becomes fully reversible in the bare iron-porphyrin complex: hemin. This leads to the speculation that the polypeptide bulk (globin) around the iron-porphyrin active site in these heme proteins is probably responsible for the electrochemical quasi reversibility. To understand the effect of such polypeptide bulk on iron-porphyrin, we study the interaction of specific amino acids with the hemin center in solution. We choose three representative amino acids-histidine (a well-known iron coordinator in bio-inorganic systems), tryptophan (a well-known fluoroprobe for proteins), and cysteine (a redox-active organic molecule). The interactions of these amino acids with hemin are studied using electrochemistry, spectroscopy, and density functional theory. The results indicate that among these three, the interaction of histidine with the iron center is strongest. Further, histidine maintains the electrochemical reversibility of iron. On the other hand, tryptophan and cysteine interact weakly with the iron center but disturb the electrochemical reversibility by contributing their own redox active processes to the system. Put together, this study attempts to understand the molecular interactions that can control electrochemical reversibility in heme proteins. The results obtained here from the three representative amino acids can be scaled up to build a heme-amino acid interaction database that may predict the electrochemical properties of any protein with a defined polypeptide sequence.

  14. Halogenation of cobalt dicarbollide

    DOEpatents

    Hurlburt, Paul K.; Abney, Kent D.; Kinkead, Scott A.

    1997-01-01

    A method for selectively adding chlorine, bromine, or iodine to cobalt dicarbollide anions by means of electrophilic substitution reactions. Halogens are added only to the B10 and B10' positions of the anion. The process involves use of hypohalous acid or N-halosuccinimide or gaseous chlorine in the presence of iron.

  15. Novel drug delivery strategies for porphyrins and porphyrin precursors

    NASA Astrophysics Data System (ADS)

    Morrow, D. I. J.; Donnelly, R. F.

    2009-06-01

    superficial lesions, such as actinic keratosis. In addition, photodynamic antimicrobial chemotherapy (PACT) is attracting increasing interest for the treatment of infection. However, delivery strategies for topical PDT and PACT are still based on application of rather simplistic cream and solution formulations, with little consideration given to thermodynamics, targeting or the physicochemical properties of the active agent. Purpose-designed dosage forms for topical delivery of aminolevulinic acid or its esters include creams containing penetration enhancers and/or iron chelators, pressure sensitive patches and bioadhesive patches. Such systems aim to enhance drug delivery across the stratum corneum and keratinised debris overlying neoplastic lesions and improve subsequent protoporphyrin IX (PpIX) production. The alternative to using porphyrin precursors is the use of pre-formed photosensitisers. However, owing to their relatively high molecular weights, conventional topical application is not appropriate. Innovative strategies, such as the use of needle-free injections and microneedle arrays, bypass the stratum corneum, enabling rapid and targeted delivery not only porphyrin precursors but also pre-formed photosensitisers. This presentation will review drug delivery work published to date in the fields of PDT and PACT. In addition, the benefits of employing the latest advances in pharmaceutical technology will be highlighted.

  16. An ultrasensitive chemiluminescence aptasensor for thrombin detection based on iron porphyrin catalyzing luminescence desorbed from chitosan modified magnetic oxide graphene composite.

    PubMed

    Sun, Yuanling; Wang, Yanhui; Li, Jianbo; Ding, Chaofan; Lin, Yanna; Sun, Weiyan; Luo, Chuannan

    2017-11-01

    In this work, an ultrasensitive chemiluminescence (CL) aptasensor was prepared for thrombin detection based on iron porphyrin catalyzing luminol - hydrogen peroxide luminescence under alkaline conditions, and iron porphyrin was desorbed from chitosan modified magnetic oxide graphene composite (CS@Fe 3 O 4 @GO). Firstly, CS@Fe 3 O 4 @GO was prepared. CS@Fe 3 O 4 @GO has advantages of the good biocompatibility and positively charged on its surface of CS, the large specific surface area of GO and the easy separation characteristics of Fe 3 O 4 . GO, Fe 3 O 4 and CS@Fe 3 O 4 @GO were confirmed by transmission electron microscopy (TEM), scanning electron microscope (SEM), fourier transform infrared (FTIR) and X-ray powder diffraction (XRD). Then, thrombin aptamer (T-Apt) and hemin (HM, an iron porphyrin) were sequentially modified on the surface of CS@Fe 3 O 4 @GO to form CS@Fe 3 O 4 @GO@T-Apt@HM. The immobilization properties of CS@Fe 3 O 4 @GO to T-Apt and adsorption properties of CS@Fe 3 O 4 @GO@T-Apt to HM were sequentially researched through the curves of kinetics and the curves of thermodynamics. When thrombin existed in solutions, HM was desorbed from the surface of CS@Fe 3 O 4 @GO@T-Apt@HM owing to the strong specific recognition ability between thrombin and T-Apt, causing the changes of CL signal. Under optimized CL conditions, thrombin could be measured with the linear concentration range of 5.0×10 -15 -2.5×10 -10 mol/L. The detection limit was 1.5×10 -15 mol/L (3δ) while the relative standard deviation (RSD) was 3.2%. Finally, the CS@Fe 3 O 4 @GO@T-Apt@HM-CL aptasensor was used for the determination of thrombin in practical serum samples and recoveries ranged from 95% to 103%. Those satisfactory results revealed potential application of the CS@Fe 3 O 4 @GO@T-Apt@HM-CL aptasensor for thrombin detection in monitoring and diagnosis of human blood diseases. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Halogenation of cobalt dicarbollide

    DOEpatents

    Hurlburt, P.K.; Abney, K.D.; Kinkead, S.A.

    1997-05-20

    A method for selectively adding chlorine, bromine, or iodine to cobalt dicarbollide anions by means of electrophilic substitution reactions. Halogens are added only to the B10 and B10{prime} positions of the anion. The process involves use of hypohalous acid or N-halosuccinimide or gaseous chlorine in the presence of iron. 1 fig.

  18. Current Issues in Molecular Catalysis Illustrated by Iron Porphyrins as Catalysts of the CO2-to-CO Electrochemical Conversion.

    PubMed

    Costentin, Cyrille; Robert, Marc; Savéant, Jean-Michel

    2015-12-15

    Recent attention aroused by the reduction of carbon dioxide has as main objective the production of useful products, the "solar fuels", in which solar energy would be stored. One route to this goal is the design of photochemical schemes that would operate this conversion using directly sun light energy. An indirect approach consists in first converting sunlight energy into electricity then using it to reduce CO2 electrochemically. Conversion of carbon dioxide into carbon monoxide is thus a key step through the classical dihydrogen-reductive Fischer-Tropsch chemistry. Direct and catalytic electrochemical CO2 reduction already aroused active interest during the 1980-1990 period. The new wave of interest for these matters that has been growing since 2012 is in direct conjunction with modern energy issues. Among molecular catalysts, electrogenerated Fe(0) porphyrins have proved to be particularly efficient and robust. Recent progress in this field has closely associated the search of more and more efficient catalysts in the iron porphyrin family with an unprecedentedly rigorous deciphering of mechanisms. Accordingly, the coupling of proton transfer with electron transfer and breaking of one of the two C-O bonds of CO2 have been the subjects of relentless scrutiny and mechanistic analysis with systematic investigation of the degree of concertedness of these three events. Catalysis of the electrochemical CO2-to-CO conversion has thus been a good testing ground for the mechanism diagnostic strategies and the all concerted reactivity model proposed then. The role of added Brönsted acids, both as H-bond providers and proton donors, has been elucidated. These efforts have been a preliminary to the inclusion of the acid functionalities within the catalyst molecule, giving rise to considerable increase of the catalytic efficiency. The design of more and more efficient catalysts made it necessary to propose "catalytic Tafel plots" relating the turnover frequency to the

  19. Method for producing iron-based catalysts

    DOEpatents

    Farcasiu, Malvina; Kaufman, Phillip B.; Diehl, J. Rodney; Kathrein, Hendrik

    1999-01-01

    A method for preparing an acid catalyst having a long shelf-life is provided comprising doping crystalline iron oxides with lattice-compatible metals and heating the now-doped oxide with halogen compounds at elevated temperatures. The invention also provides for a catalyst comprising an iron oxide particle having a predetermined lattice structure, one or more metal dopants for said iron oxide, said dopants having an ionic radius compatible with said lattice structure; and a halogen bound with the iron and the metal dopants on the surface of the particle.

  20. Detection of Carbon Monoxide Using Polymer-Composite Films with a Porphyrin-Functionalized Polypyrrole

    NASA Technical Reports Server (NTRS)

    Homer, Margie L.; Ryan, Margaret A.; Yen, Shiao-Ping S.; Lara, Liana M.; Shevade, Abhijit V.; Kisor, Adam

    2012-01-01

    Post-fire air constituents that are of interest to NASA include CO and some acid gases (HCl and HCN). CO is an important analyte to be able to sense in human habitats since it is a marker for both prefire detection and post-fire cleanup. The need exists for a sensor that can be incorporated into an existing sensing array architecture. The CO sensor needs to be a low-power chemiresistor that operates at room temperature; the sensor fabrication techniques must be compatible with ceramic substrates. Early work on the JPL ElectronicNose indicated that some of the existing polymer-carbon black sensors might be suitable. In addition, the CO sensor based on polypyrrole functionalized with iron porphyrin was demonstrated to be a promising sensor that could meet the requirements. First, pyrrole was polymerized in a ferric chloride/iron porphyrin solution in methanol. The iron porphyrin is 5, 10, 15, 20-tetraphenyl-21H, 23Hporphine iron (III) chloride. This creates a polypyrrole that is functionalized with the porphyrin. After synthesis, the polymer is dried in an oven. Sensors were made from the functionalized polypyrrole by binding it with a small amount of polyethylene oxide (600 MW). This composite made films that were too resistive to be measured in the device. Subsequently, carbon black was added to the composite to bring the sensing film resistivity within a measurable range. A suspension was created in methanol using the functionalized polypyrrole (90% by weight), polyethylene oxide (600,000 MW, 5% by weight), and carbon black (5% by weight). The sensing films were then deposited, like the polymer-carbon black sensors. After deposition, the substrates were dried in a vacuum oven for four hours at 60 C. These sensors showed good response to CO at concentrations over 100 ppm. While the sensor is based on a functionalized pyrrole, the actual composite is more robust and flexible. A polymer binder was added to help keep the sensor material from delaminating from the

  1. Push-pull quinoidal porphyrins.

    PubMed

    Smith, Martin J; Blake, Iain M; Clegg, William; Anderson, Harry L

    2018-05-01

    A family of push-pull quinoidal porphyrin monomers has been prepared from a meso-formyl porphyrin by bromination, thioacetal formation, palladium-catalyzed coupling with malononitrile and oxidation with DDQ. Attempts at extending this synthesis to a push-pull quinoidal/cumulenic porphyrin dimer were not successful. The crystal structures of the quinoidal porphyrins indicate that there is no significant contribution from singlet biradical or zwitterionic resonance forms. The crystal structure of an ethyne-linked porphyrin dimer shows that the torsion angle between the porphyrin units is only about 3°, in keeping with crystallographic results on related compounds, but contrasting with the torsion angle of about 35° predicted by computational studies. The free-base quinoidal porphyrin monomers form tightly π-stacked layer structures, despite their curved geometries and bulky aryl substituents.

  2. Fragmentation dynamics of meso-tetraphenyl iron (III) porphyrin chloride dication under energy control

    NASA Astrophysics Data System (ADS)

    Li, B.; Allouche, A. R.; Bernard, J.; Brédy, R.; Qian, D. B.; Ma, X.; Martin, S.; Chen, L.

    2017-03-01

    Meso-tetraphenyl iron (III) porphyrin chloride dications (FeTPPCl2+)* were prepared in collisions with F+ and H+ at 3 keV. The dominant fragmentation channels were observed to involve the loss of the Cl atom and the successive loss of neutral phenyl groups for both collisional systems. The mass spectra in correlation with the deposited excitation energy distributions of the parent ions for the main fragmentation channels were measured by using the collision induced dissociation under energy control method. The global excitation energy distribution was found to be shifted to lower energies in collisions with H+ compared to collisions with F+ showing a noteworthy change of the excitation energy window using different projectile ions. Partial excitation energy distributions of the parent ions FeTPPCl2+ were obtained for each fragmentation group. In a theoretical work, we have calculated the dissociation energies for the loss of one and two phenyl groups, including phenyl and (phenyl ± H). The energy barrier for the hydrogen atom transfer during the loss of (phenyl-H) has been also calculated. The measured energy difference for the successive loss of two phenyl groups was compared with the theoretical values.

  3. Synthesis of porphyrin nanostructures

    DOEpatents

    Fan, Hongyou; Bai, Feng

    2014-10-28

    The present disclosure generally relates to self-assembly methods for generating porphyrin nanostructures. For example, in one embodiment a method is provided that includes preparing a porphyrin solution and a surfactant solution. The porphyrin solution is then mixed with the surfactant solution at a concentration sufficient for confinement of the porphyrin molecules by the surfactant molecules. In some embodiments, the concentration of the surfactant is at or above its critical micelle concentration (CMC), which allows the surfactant to template the growth of the nanostructure over time. The size and morphology of the nanostructures may be affected by the type of porphyrin molecules used, the type of surfactant used, the concentration of the porphyrin and surfactant the pH of the mixture of the solutions, and the order of adding the reagents to the mixture, to name a few variables.

  4. Structural Perspective on Enzymatic Halogenation

    PubMed Central

    2008-01-01

    and chemistry of these enzymes. In particular, the latest crystallographic snapshots of active site architecture and halide binding sites have provided key insights into enzyme catalysis. Herein is a summary of the five classes of halogenases, focusing on the three most recently discovered: flavin-dependent halogenases, non-heme iron-dependent halogenases, and nucleophilic halogenases. Further, the potential roles of halide-binding sites in determining halide selectivity are discussed, as well as whether or not binding-site composition is always a seminal factor for selectivity. Expanding our understanding of the basic chemical principles that dictate the activity of the halogenases will advance both biology and chemistry. A thorough mechanistic analysis will elucidate the biological principles that dictate specificity, and the application of those principles to new synthetic techniques will expand the utility of halogenations in small-molecule development. PMID:18774824

  5. Porphyrin amino acids-amide coupling, redox and photophysical properties of bis(porphyrin) amides.

    PubMed

    Melomedov, Jascha; Wünsche von Leupoldt, Anica; Meister, Michael; Laquai, Frédéric; Heinze, Katja

    2013-07-14

    New trans-AB2C meso-substituted porphyrin amino acid esters with meso-substituents of tunable electron withdrawing power (B = mesityl, 4-C6H4F, 4-C6H4CF3, C6F5) were prepared as free amines 3a-3d, as N-acetylated derivatives Ac-3a-Ac-3d and corresponding zinc(II) complexes Zn-Ac-3a-Zn-Ac-3d. Several amide-linked bis(porphyrins) with a tunable electron density at each porphyrin site were obtained from the amino porphyrin precursors by condensation reactions (4a-4d) and mono- and bis(zinc(II)) complexes Zn(2)-4d and Zn(1)Zn(2)-4d were prepared. The electronic interaction between individual porphyrin units in bis(porphyrins) 4 is probed by electrochemical experiments (CV, EPR), electronic absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy in combination with DFT/PCM calculations on diamagnetic neutral bis(porphyrins) 4 and on respective charged mixed-valent radicals 4(+/-). The interaction via the -C6H4-NHCO-C6H4- bridge, the site of oxidation and reduction and the lowest excited singlet state S1, is tuned by the substituents on the individual porphyrins and the metalation state.

  6. Manganese Catalyzed C–H Halogenation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Wei; Groves, John T.

    2015-06-16

    The remarkable aliphatic C–H hydroxylations catalyzed by the heme-containing enzyme, cytochrome P450, have attracted sustained attention for more than four decades. The effectiveness of P450 enzymes as highly selective biocatalysts for a wide range of oxygenation reactions of complex substrates has driven chemists to develop synthetic metalloporphyrin model compounds that mimic P450 reactivity. Among various known metalloporphyrins, manganese derivatives have received considerable attention since they have been shown to be versatile and powerful mediators for alkane hydroxylation and olefin epoxidation. Mechanistic studies have shown that the key intermediates of the manganese porphyrin-catalyzed oxygenation reactions include oxo- and dioxomanganese(V) species thatmore » transfer an oxygen atom to the substrate through a hydrogen abstraction/oxygen recombination pathway known as the oxygen rebound mechanism. Application of manganese porphyrins has been largely restricted to catalysis of oxygenation reactions until recently, however, due to ultrafast oxygen transfer rates. In this Account, we discuss recently developed carbon–halogen bond formation, including fluorination reactions catalyzed by manganese porphyrins and related salen species. We found that biphasic sodium hypochlorite/manganese porphyrin systems can efficiently and selectively convert even unactivated aliphatic C–H bonds to C–Cl bonds. An understanding of this novel reactivity derived from results obtained for the oxidation of the mechanistically diagnostic substrate and radical clock, norcarane. Significantly, the oxygen rebound rate in Mn-mediated hydroxylation is highly correlated with the nature of the trans-axial ligands bound to the manganese center (L–Mn V$=$O). Based on the ability of fluoride ion to decelerate the oxygen rebound step, we envisaged that a relatively long-lived substrate radical could be trapped by a Mn–F fluorine source, effecting carbon–fluorine bond

  7. Self-Assembly of Porphyrin J-Aggregates

    NASA Astrophysics Data System (ADS)

    Snitka, Valentinas; Rackaitis, Mindaugas; Navickaite, Gintare

    2006-03-01

    The porphyrin nanotubes were built by ionic self-assembly of two oppositely charged porphyrins in aqueous solution. The porphyrins in the acid aqueous solution self-assemble into J-aggregates, wheels or other structures. The electrostatic forces between these porphyrin blocks contribute to the formation of porphyrin aggregates in the form of nanotubes, enhance the structural stability of these nanostructures. The nanotubes were composed mixing aqueous solutions of the two porphyrins - anionic Meso-tetra(4- sulfonatophrnyl)porhine dihydrochloride (TPPS4) and cationic Meso-tetra(4-pyridyl)porphine (T4MPyP). The porphyrin nanotubes obtained are hollow structures with the length of 300 nm and diameter 50 nm. Photocatalytic porphyrins are used to reduce metal complexes from aqueous solution and to control the deposition of Au from AuHCl4 and Au nanoparticles colloid solutions onto porphyrin nanotubes. Porphyrin nanotubes are shown to reduce metal complexes and deposit the metal selectively onto the inner or outer surface of the tubes, leading to nanotube-metal composite structures.

  8. Method for oxidizing alkanes using novel porphyrins synthesized from dipyrromethanes and aldehydes

    DOEpatents

    Wijesekera, Tilak; Lyons, James E.; Ellis, Jr., Paul E.

    1999-01-01

    The invention comprises a method for the oxidation of alkanes to alcohols and for decomposition of hydroperoxides to alcohols utilizing new compositions of matter, which are metal complexes of porphyrins. Preferred complexes have hydrogen, haloalkyl or haloaryl groups in meso positions, two of the opposed meso atoms or groups being hydrogen or haloaryl, and two of the opposed meso atoms or groups being hydrogen or haloalkyl, but not all four of the meso atoms or groups being hydrogen. Other preferred complexes are ones in which all four of the meso positions are substituted with haloalkyl groups and the beta positions are substituted with halogen atoms. A new method of synthesizing porphyrinogens is also disclosed.

  9. Method for hydroperoxide decomposition using novel porphyrins synthesized from dipyrromethanes and aldehydes

    DOEpatents

    Wijesekera, T.; Lyons, J.E.; Ellis, P.E. Jr.

    1998-03-03

    The invention comprises a method for the oxidation of alkanes to alcohols and for decomposition of hydroperoxides to alcohols utilizing new compositions of matter, which are metal complexes of porphyrins. Preferred complexes have hydrogen, haloalkyl or haloaryl groups in meso positions, two of the opposed meso atoms or groups being hydrogen or haloaryl, and two of the opposed meso atoms or groups being hydrogen or haloalkyl, but not all four of the meso atoms or groups being hydrogen. Other preferred complexes are ones in which all four of the meso positions are substituted with haloalkyl groups and the beta positions are substituted with halogen atoms. A new method of synthesizing porphyrinogens is also disclosed.

  10. Method for hydroperoxide decomposition using novel porphyrins synthesized from dipyrromethanes and aldehydes

    DOEpatents

    Wijesekera, Tilak; Lyons, James E.; Ellis, Jr., Paul E.

    1998-01-01

    The invention comprises a method for the oxidation of alkanes to alcohols and for decomposition of hydroperoxides to alcohols utilizing new compositions of matter, which are metal complexes of porphyrins. Preferred complexes have hydrogen, haloalkyl or haloaryl groups in meso positions, two of the opposed meso atoms or groups being hydrogen or haloaryl, and two of the opposed meso atoms or groups being hydrogen or haloalkyl, but not all four of the meso atoms or groups being hydrogen. Other preferred complexes are ones in which all four of the meso positions are substituted with haloalkyl groups and the beta positions are substituted with halogen atoms. A new method of synthesizing porphyrinogens is also disclosed.

  11. 40 CFR 65.154 - Halogen scrubbers and other halogen reduction devices.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 15 2011-07-01 2011-07-01 false Halogen scrubbers and other halogen... Routing to a Fuel Gas System or a Process § 65.154 Halogen scrubbers and other halogen reduction devices. (a) Halogen scrubber and other halogen reduction device equipment and operating requirements. (1) An...

  12. Graphene oxide vs. reduced graphene oxide as carbon support in porphyrin peroxidase biomimetic nanomaterials.

    PubMed

    Socaci, C; Pogacean, F; Biris, A R; Coros, M; Rosu, M C; Magerusan, L; Katona, G; Pruneanu, S

    2016-02-01

    The paper describes the preparation of supramolecular assemblies of tetrapyridylporphyrin (TPyP) and its metallic complexes with graphene oxide (GO) and thermally reduced graphene oxide (TRGO). The two carbon supports are introducing different characteristics in the absorption spectra of the investigated nanocomposites. Raman spectroscopy shows that the absorption of iron-tetrapyridylporphyrin is more efficient on GO than TRGO, suggesting that oxygen functionalities are involved in the non-covalent interaction between the iron-porphyrin and graphene. The biomimetic peroxidase activity is investigated and the two iron-containing composites exhibit a better catalytic activity than each component of the assembly, and their cobalt and manganese homologues, respectively. The main advantages of this work include the demonstration of graphene oxide as a very good support for graphene-based nanomaterials with peroxidase-like activity (K(M)=0.292 mM), the catalytic activity being observed even with very small amounts of porphyrins (the TPyP:graphene ratio=1:50). Its potential application in the detection of lipophilic antioxidants (vitamin E can be measured in the 10(-5)-10(-4) M range) is also shown. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Effect of the protoporphyrinogen oxidase-inhibiting herbicide fomesafen on liver uroporphyrin and heptacarboxylic porphyrin in two mouse strains.

    PubMed

    Krijt, J; Vokurka, M; Sanitrak, J; Janousek, V; van Holsteijn, I; Blaauboer, B J

    1994-07-01

    The effect of the protoporphyrinogen oxidase-inhibiting herbicide fomesafen on liver porphyrin accumulation was studied in long-term high-dose experiments. Fomesafen caused liver accumulation of uroporphyrin and heptacarboxylic porphyrin when fed at 0.25% in the diet to male ICR mice for 5 months (fomesafen-treated mice: 52 nmol uroporphyrin, 21 nmol heptacarboxylic porphyrin/g liver; control mice: traces of uroporphyrin, heptacarboxylic porphyrin not detected). Uroporphyrinogen decarboxylase activity was depressed to about 25% of control values. Iron treatment accelerated the development of this porphyria cutanea tarda-like experimental porphyria both in ICR and C57B1/6J mice. In contrast to other uroporphyrinogen decarboxylase inhibitors, fomesafen treatment did not increase the cytochrome P450IA-related activities and the amount of P450IA2 protein was shown to be significantly decreased by Western immunoblotting. Thus, fomesafen is a unique chemical that inhibits both the oxidation of protoporphyrinogen as well as the conversion of uroporphyrinogen to coproporphyrinogen. However, the accumulation of highly carboxylated porphyrins is evident only after prolonged treatment with high doses of the herbicide.

  14. A review of iron and cobalt porphyrins, phthalocyanines, and related complexes for electrochemical and photochemical reduction of carbon dioxide

    DOE PAGES

    Manbeck, Gerald F.; Fujita, Etsuko

    2015-03-30

    This review summarizes research on the electrochemical and photochemical reduction of CO₂ using a variety of iron and cobalt porphyrins, phthalocyanines, and related complexes. Metalloporphyrins and metallophthalocyanines are visible light absorbers with extremely large extinction coefficients. However, yields of photochemically-generated active catalysts for CO₂ reduction are typically low owing to the requirement of a second photoinduced electron. This requirement is not relevant to the case of electrochemical CO₂ reduction. Recent progress on efficient and stable electrochemical systems includes the use of FeTPP catalysts that have prepositioned phenyl OH groups in their second coordination spheres. This has led to remarkable progressmore » in carrying out coupled proton-electron transfer reactions for CO₂ reduction. Such ground-breaking research has to be continued in order to produce renewable fuels in an economically feasible manner.« less

  15. Functionalized expanded porphyrins

    DOEpatents

    Sessler, Jonathan L; Pantos, Patricia J

    2013-11-12

    Disclosed are functionalized expanded porphyrins that can be used as spectrometric sensors for high-valent actinide cations. The disclosed functionalized expanded porphyrins have the advantage over unfunctionalized systems in that they can be immobilized via covalent attachment to a solid support comprising an inorganic or organic polymer or other common substrates. Substrates comprising the disclosed functionalized expanded porphyrins are also disclosed. Further, disclosed are methods of making the disclosed compounds (immobilized and free), methods of using them as sensors to detect high valent actinides, devices that comprise the disclosed compounds, and kits.

  16. Impact of substituents and nonplanarity on nickel and copper porphyrin electrochemistry: first observation of a Cu(II)/Cu(III) reaction in nonaqueous media.

    PubMed

    Fang, Yuanyuan; Senge, Mathias O; Van Caemelbecke, Eric; Smith, Kevin M; Medforth, Craig J; Zhang, Min; Kadish, Karl M

    2014-10-06

    Electrochemical studies of the oxidation of dodecasubstituted and highly nonplanar nickel porphyrins in a noncoordinating solvent have previously revealed the first nickel(III) porphyrin dication. Herein, we investigate if these nonplanar porphyrins can also be used to detect the so far unobserved copper(III) porphyrin dication. Electrochemical studies of the oxidation of (DPP)Cu and (OETPP)Cu show three processes, the first two of which are macrocycle-centered to give the porphyrin dication followed by a Cu(II)/Cu(III) process at more positive potential. Support for the assignment of the Cu(II)/Cu(III) process comes from the linear relationships observed between E1/2 and the third ionization potential of the central metal ions for iron, cobalt, nickel, and copper complexes of (DPP)M and (OETPP)M. In addition, the oxidation behavior of additional nonplanar nickel porphyrins is investigated in a noncoordinating solvent, with nickel meso-tetraalkylporphyrins also being found to form nickel(III) porphyrin dications. Finally, examination of the nickel meso-tetraalkylporphyrins in a coordinating solvent (pyridine) reveals that the first oxidation becomes metal-centered under these conditions, as was previously noted for a range of nominally planar porphyrins.

  17. Impact of Substituents and Nonplanarity on Nickel and Copper Porphyrin Electrochemistry: First Observation of a CuII/CuIII Reaction in Nonaqueous Media

    PubMed Central

    2015-01-01

    Electrochemical studies of the oxidation of dodecasubstituted and highly nonplanar nickel porphyrins in a noncoordinating solvent have previously revealed the first nickel(III) porphyrin dication. Herein, we investigate if these nonplanar porphyrins can also be used to detect the so far unobserved copper(III) porphyrin dication. Electrochemical studies of the oxidation of (DPP)Cu and (OETPP)Cu show three processes, the first two of which are macrocycle-centered to give the porphyrin dication followed by a CuII/CuIII process at more positive potential. Support for the assignment of the CuII/CuIII process comes from the linear relationships observed between E1/2 and the third ionization potential of the central metal ions for iron, cobalt, nickel, and copper complexes of (DPP)M and (OETPP)M. In addition, the oxidation behavior of additional nonplanar nickel porphyrins is investigated in a noncoordinating solvent, with nickel meso-tetraalkylporphyrins also being found to form nickel(III) porphyrin dications. Finally, examination of the nickel meso-tetraalkylporphyrins in a coordinating solvent (pyridine) reveals that the first oxidation becomes metal-centered under these conditions, as was previously noted for a range of nominally planar porphyrins. PMID:25253031

  18. A moderate distortion of the `picket-fence' porphyrin (cryptand-222)potassium chlorido[meso-α,α,α,α-tetrakis(o-pivalamidophenyl)porphyrinato]ferrate(II) n-hexane monosolvate.

    PubMed

    Yu, Qiang; Liu, Diansheng; Li, Xiangjun; Li, Jianfeng

    2015-10-01

    As representative porphyrin model compounds, the structures of `picket-fence' porphyrins have been studied intensively. The title solvated complex salt {systematic name: (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane)potassium(I) [5,10,15,20-tetrakis(2-tert-butanamidophenyl)porphyrinato]iron(II) n-hexane monosolvate}, [K(C18H36N2O6)][Fe(C64H64N8O4)Cl]·C6H14 or [K(222)][Fe(TpivPP)Cl]·C6H14 [222 is cryptand-222 or 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane, and TpivPP is meso-α,α,α,α-tetrakis(o-pivalamidophenyl)porphyrinate(2-)], [K(222)][Fe(TpivPP)Cl]·C6H14, is a five-coordinate high-spin iron(II) picket-fence porphyrin complex. It crystallizes with a potassium cation chelated inside a cryptand-222 molecule; the average K-O and K-N distances are 2.81 (2) and 3.05 (2) Å, respectively. One of the protecting tert-butyl pickets is disordered. The porphyrin plane presents a moderately ruffled distortion, as suggested by the atomic displacements. The axial chloride ligand is located inside the molecular cavity on the hindered porphyrin side and the Fe-Cl bond is tilted slightly off the normal to the porphyrin plane by 4.1°. The out-of-plane displacement of the metal centre relative to the 24-atom mean plane (Δ24) is 0.62 Å, indicating a noticeable doming of the porphyrin core.

  19. 40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

  20. 40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

  1. 40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

  2. 40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

  3. 40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

  4. HALOGENATED AROMATIC HYDROCARBON-MEDIATED PORPHYRIN ACCUMULATION AND INDUCTION OF CYTOCHROME P4501A IN CHICKEN EMBRYO HEPATOCYTES. (R823889)

    EPA Science Inventory

    Concentration-dependent induction of cytochrome P4501A (CYP1A) and intracellular porphyrin accumulation were observed following treatment of chicken embryo hepatocyte (CEH) cultures with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), 3,3',4,4'...

  5. A facile approach towards increasing the nitrogen-content in nitrogen-doped carbon nanotubes via halogenated catalysts

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ombaka, L.M.; Ndungu, P.G.; Department of Applied Chemistry, Doornfontein Campus, University of Johannesburg, P.O. Box 17011, Johannesburg 2028

    Nitrogen-doped carbon nanotubes (N-CNTs) have been synthesized at 850 °C via a CVD deposition technique by use of three ferrocenyl derivative catalysts, i.e. para-CN, -CF{sub 3} and -Cl substituted-phenyl rings. The synthesized catalysts have been characterized by NMR, IR, HR-MS and XRD. The XRD analysis of the para-CF{sub 3} catalyst indicates that steric factors influence the X-ray structure of 1,1′-ferrocenylphenyldiacrylonitriles. Acetonitrile or pyridine was used as carbon and nitrogen sources to yield mixtures of N-CNTs and carbon spheres (CS). The N-CNTs obtained from the para-CF{sub 3} catalysts, in pyridine, have the highest nitrogen-doping level, show a helical morphology and aremore » less thermally stable compared with those synthesized by use of the para-CN and -Cl as catalyst. This suggests that fluorine heteroatoms enhance nitrogen-doping in N-CNTs and formation of helical-N-CNTs (H-N-CNTs). The para-CF{sub 3} and para-Cl catalysts in acetonitrile yielded iron-filled N-CNTs, indicating that halogens promote encapsulation of iron into the cavity of N-CNT. The use of acetonitrile, as carbon and nitrogen source, with the para-CN and -Cl as catalysts also yielded a mixture of N-CNTs and carbon nanofibres (CNFs), with less abundance of CNFs in the products obtained using para-Cl catalysts. However, para-CF{sub 3} catalyst in acetonitrile gave N-CNTs as the only shaped carbon nanomaterials. - Graphical abstract: Graphical abstract showing the synthesis of N-CNTs using halogenated-ferrocenyl derivatives as catalyst with pyridine or acetonitrile as nitrogen and carbon sources via the chemical vapour deposition technique. - Highlights: • N-CNTs were synthesized from halogenated ferrocenyl catalysts. • Halogenated catalysts promote nitrogen-doping and pyridinic nitrogen in N-CNTs. • Halogenated catalysts facilitate iron filling of N-CNTs.« less

  6. Soluble porphyrin polymers

    DOEpatents

    Gust, Jr., John Devens; Liddell, Paul Anthony

    2015-07-07

    Porphyrin polymers of Structure 1, where n is an integer (e.g., 1, 2, 3, 4, 5, or greater) ##STR00001## are synthesized by the method shown in FIGS. 2A and 2B. The porphyrin polymers of Structure 1 are soluble in organic solvents such as 2-MeTHF and the like, and can be synthesized in bulk (i.e., in processes other than electropolymerization). These porphyrin polymers have long excited state lifetimes, making the material suitable as an organic semiconductor for organic electronic devices including transistors and memories, as well as solar cells, sensors, light-emitting devices, and other opto-electronic devices.

  7. Dimerization of tetracationic porphyrins: ionic strength dependence.

    PubMed

    Dixon, D W; Steullet, V

    1998-02-01

    Cationic porphyrins are under study in a number of contexts including their interaction with biological targets, as possible therapeutic agents and as building blocks for molecular devices such as molecular photodiodes and solar cells. Many cationic porphyrins dimerize readily in aqueous solution. Dimerization in turn can control the properties of the porphyrin as well as its binding to its target. The propensity of a porphyrin to dimerize in aqueous solution can be estimated by recording the optical spectrum of the solution as a function of the concentration of added salt. Analysis of the data in terms of the Debye-Hückel formalism gives an estimate of the extent of dimerization as a function of ionic strength. Data for TMPyP4 [meso-tetrakis(4-N-methylpyridinium)porphyrin] and its butyl and octyl homologs; TMAP [meso-tetrakis(4-N,N,N-trimethylanilinium)porphyrin]; T theta PP [meso-tetrakis[4-N-[(3-(trimethyl-ammonio)propyl)oxy]phenyl]porphyrin] and the ferrocenyl porphyrin P3Fc are discussed. Dimerization may affect binding of the cationic porphyrins to their targets, e.g., DNA.

  8. Halogen radicals contribute to photooxidation in coastal and estuarine waters

    PubMed Central

    Parker, Kimberly M.; Mitch, William A.

    2016-01-01

    Although halogen radicals are recognized to form as products of hydroxyl radical (•OH) scavenging by halides, their contribution to the phototransformation of marine organic compounds has received little attention. We demonstrate that, relative to freshwater conditions, seawater halides can increase photodegradation rates of domoic acid, a marine algal toxin, and dimethyl sulfide, a volatile precursor to cloud condensation nuclei, up to fivefold. Using synthetic seawater solutions, we show that the increased photodegradation is specific to dissolved organic matter (DOM) and halides, rather than other seawater salt constituents (e.g., carbonates) or photoactive species (e.g., iron and nitrate). Experiments in synthetic and natural coastal and estuarine water samples demonstrate that the halide-specific increase in photodegradation could be attributed to photochemically generated halogen radicals rather than other photoproduced reactive intermediates [e.g., excited-state triplet DOM (3DOM*), reactive oxygen species]. Computational kinetic modeling indicates that seawater halogen radical concentrations are two to three orders of magnitude greater than freshwater •OH concentrations and sufficient to account for the observed halide-specific increase in photodegradation. Dark •OH generation by gamma radiolysis demonstrates that halogen radical production via •OH scavenging by halides is insufficient to explain the observed effect. Using sensitizer models for DOM chromophores, we show that halogen radicals are formed predominantly by direct oxidation of Cl− and Br− by 3DOM*, an •OH-independent pathway. Our results indicate that halogen radicals significantly contribute to the phototransformation of algal products in coastal or estuarine surface waters. PMID:27162335

  9. Synthesis of borylated porphyrin and bromo- porphyrin as building blocks for light harvesting antenna molecule

    NASA Astrophysics Data System (ADS)

    Radzuan, Nuur Haziqah Mohd; Hassan, Nurul Izzaty; Bakar, Muntaz Abu

    2018-04-01

    The building blocks for synthesis of light harvesting antenna which are 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolane)-10,20-diphenylporphyrin, 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolane)-10,20-dihexylporphyrin and 5,10,15,20-tetra-(bromophenyl)porphyrin were synthesized. Borylated porphyrin was synthesized by Suzuki coupling reaction between A2BC bromo-porphyrin and pinacolborane. Whereas 5,10,15,20-tetra-(bromophenyl) porphyrin was synthesized by Lindsey condensation reaction between pyrrole and 4-bromobenzaldehyde. 1H-NMR, 13C-NMR spectroscopy and UV-visible spectroscopy confirmed the successful formation of all compounds.

  10. Three Short Stories about Hexaarylbenzene-Porphyrin Scaffolds.

    PubMed

    Lungerich, Dominik; Hitzenberger, Jakob F; Donaubauer, Wolfgang; Drewello, Thomas; Jux, Norbert

    2016-11-14

    A feasible two-step synthesis and characterization of a full series of hexaarylbenzene (HAB) substituted porphyrins and tetrabenzoporphyrins is presented. Key steps represent the microwave-assisted porphyrin condensation and the statistical Diels-Alder reaction to the desired HAB-porphyrins. Regarding their applications, they proved to be easily accessible and effective high molecular mass calibrants for (MA)LDI mass spectrometry. The free-base and zinc(II) porphyrin systems, as well as the respective tetrabenzoporphyrins, demonstrate in solid state experiments strong red- and near-infrared-light emission and are potentially interesting for the application in "truly organic" light-emitting devices. Lastly, they represent facile precursors to large polycyclic aromatic hydrocarbon (PAH) substituted porphyrins. We prepared the first tetra-hexa-peri-hexabenzocoronene substituted porphyrin, which represents the largest prepared PAH-porphyrin conjugate to date. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Relativistic effects in iron-, ruthenium-, and osmium porphyrins

    NASA Astrophysics Data System (ADS)

    Liao, Meng-Sheng; Scheiner, Steve

    2002-12-01

    Nonrelativistic and relativistic DFT calculations are performed on four-coordinate metal porphyrins MP and their six-coordinate adducts MP(py) 2 and MP(py)(CO) (py=pyridine) with M=Fe, Ru, and Os. The electronic structures of the MPs are investigated by considering all possible low-lying states with different configurations of nd-electrons. FeP and OsP have a 3A2 g ground state, while this state is nearly degenerate with 3Eg for RuP. Without relativistic corrections, the ground states of both RuP and OsP would be 3Eg. For the six-coordinate adducts with py and CO, the strong-field axial ligands raise the energy of the M d z2-orbital, thereby making the M II ion diamagnetic. The calculated redox properties of MP(py) 2 and MP(py)(CO) are in agreement with experiment. The difference between RuP(py)(CO) and OsP(py)(CO), in terms of site of oxidation, is due to relativistic effects.

  12. Antimicrobial activity of new porphyrins of synthetic and natural origin

    NASA Astrophysics Data System (ADS)

    Gyulkhandanyan, Grigor V.; Ghazaryan, Robert K.; Paronyan, Marina H.; Ulikhanyan, Ghukas I.; Gyulkhandanyan, Aram G.; Sahakyan, Lida A.

    2012-03-01

    Antimicrobial photodynamic inactivation has been successfully used against Gram (+) microorganisms, but most of the photosensitizers (PSs) on Gram (-) bacteria acts weakly. PSs are the natural or synthetic origin dyes, mainly porphyrins. We have synthesized more than 100 new cationic porphyrins and metalloporphyrins with different functional groups (hydroxyethyl, butyl, allyl, methallyl) and metals (cobalt, iron, copper, zinc, silver and other); from the nettle have also been purified pheophytin (a+b) and pheophytin (a) and have synthesized their Ag-and Zn-metalloporphyrins. It was found that in the dark (cytotoxic) mode, the most highly efficiency against microorganisms showed Agmetalloporphyrins of both types of porphyrins (synthetic and natural). Metalloporphyrin of natural origin Ag-pheophytin (a + b) is a strong antibacterial agent and causes 100% death as the Gram (+) microorganisms (St. aureus and MRSA) and the Gram (-) microorganisms (E.coli and Salmonella). It is established that for the destruction of Gram (+) and Gram (-) microorganisms in photodynamic mode cationic water-soluble synthetic metalloporphyrins, especially Zn-TBut4PyP, many times more effective than pheophytins. In vivo conditions on mice established that the best therapeutic activity against various strains of the microorganism St. aureus has the synthetic metalloporphyrin Ag-TBut4PyP. It is significantly more efficient than known drug "Chlorophyllipt" (2.5-3 times) and leads the survival rate of animals up to 50-60%.

  13. Porphyrin coordination polymer nanospheres and nanorods

    DOEpatents

    Wang, Zhongchun; Shelnutt, John A.; Medforth, Craig J.

    2012-12-04

    A porphyrin coordination polymer nanostructure comprising a network of pyridyl porphyrin molecules and coordinating metal ions coordinatively bound through the pyridyl groups. In some embodiments, the porphyrins are metalloporphyrins. A variety of nanostructures are formed by the network polymer, including nanospheres, polygonal nanostructures, nanorods, and nanofibers, depending on a variety of factors including coordination metal ion, porphyrin type, metal of the metalloporphyrin, and degree of agitation during nanostructure formation. Reduction of coordinating metal ions may be used to form metal nanoparticles on the coordination polymer nanostructure.

  14. Porphyrin coordination polymer nanospheres and nanorods

    DOEpatents

    Wang, Zhongchun; Shelnutt, John A.; Medforth, Craig J.

    2013-09-10

    A porphyrin coordination polymer nanostructure comprising a network of pyridyl porphyrin molecules and coordinating metal ions coordinatively bound through the pyridyl groups. In some embodiments, the porphyrins are metalloporphyrins. A variety of nanostructures are formed by the network polymer, including nanospheres, polygonal nanostructures, nanorods, and nanofibers, depending on a variety of factors including coordination metal ion, porphyrin type, metal of the metalloporphyrin, and degree of agitation during nanostructure formation. Reduction of coordinating metal ions may be used to form metal nanoparticles on the coordination polymer nanostructure.

  15. Stepwise syntheses of bisporphyrins, bischlorins, and biscorroles and of porphyrin-chlorin and porphyrin-corrole heterodimers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Paolesse, R.; Pandey, R.K.; Forsyth, T.P.

    The stepwise syntheses and characterization of a series of symmetrical and unsymmetrical bisporphyrins, bischlorins, and biscorroles, and of porphyrin-chlorin and porphyrin-corrole dyads possessing ethylene, phenyl, and stilbene linking units are described. The methodology for synthesis of 10-substituted corroles 2 and their cobalt complexes 9 via a,c-biladiene salts 1 was first developed, and then extended to provide biscorroles (e.g., 4 and 5) linked through the 10-positions with phenyl linker units. Using a similar methodology, phenyl-linked corrole-porphyrin dyads 28 and 30 were also prepared. By way of intermediate phenyl-linked unsymmetrical bisdipyrromethanes, a completely unsymmetrical heterobimetallic bisporphyrin system, 45, was synthesized. Low-valent titaniummore » coupling (McMurry) reactions were used to prepare stilbene-linked bisdipyrromethanes (e.g., 46) which were subsequently transformed into stilbene-linked bisporphyrins (e.g., 48). McMurry cross-coupling reactions of porphyrins bearing p-formylphenyl substituents also afforded an unsymmetrically substituted bisporphyrinylstilbene, 60, as well as the corresponding homodimers 56 and 59. Likewise, McMurry cross-coupling of a p-formylphenyl-substituted porphyrin, 62, with a formylchlorin, 63, afforded a stilbene-linked bisporphyrin, 64, a bischlorin, 66, and a novel porphyrin-chlorin heterodimer, 65. 54 refs., 1 fig., 1 tab.« less

  16. Efficient solar-assisted O2 reduction by a cofacial iron porphyrin dimer integrated to a p-CuBi2O4 photocathode prepared by a simple novel method.

    PubMed

    Zahran, Zaki N; Mohamed, Eman A; Naruta, Yoshinori; Haleem, Ashraf

    2017-10-04

    A cofacial iron porphyrin hetero-dimer, Fe2TPFPP-TMP showed high electro-catalytic activity, selectivity, and stability for the O2 reduction to H2O both in homogeneous non-aqueous and heterogeneous neutral aqueous solutions. Moreover, when it is integrated to FTO/p-CuBi2O4 (FTO = fluorine doped tin oxide) photocathode prepared by a simple novel method, a remarkable efficient solar-assisted O2 reduction is achieved in neutral potassium phosphate (KPi) or basic NaOH solutions saturated with O2. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Hemoglobin-derived porphyrins preserved in a Middle Eocene blood-engorged mosquito

    PubMed Central

    Greenwalt, Dale E.; Goreva, Yulia S.; Siljeström, Sandra M.; Rose, Tim; Harbach, Ralph E.

    2013-01-01

    Although hematophagy is found in ∼14,000 species of extant insects, the fossil record of blood-feeding insects is extremely poor and largely confined to specimens identified as hematophagic based on their taxonomic affinities with extant hematophagic insects; direct evidence of hematophagy is limited to four insect fossils in which trypanosomes and the malarial protozoan Plasmodium have been found. Here, we describe a blood-engorged mosquito from the Middle Eocene Kishenehn Formation in Montana. This unique specimen provided the opportunity to ask whether or not hemoglobin, or biomolecules derived from hemoglobin, were preserved in the fossilized blood meal. The abdomen of the fossil mosquito was shown to contain very high levels of iron, and mass spectrometry data provided a convincing identification of porphyrin molecules derived from the oxygen-carrying heme moiety of hemoglobin. These data confirm the existence of taphonomic conditions conducive to the preservation of biomolecules through deep time and support previous reports of the existence of heme-derived porphyrins in terrestrial fossils. PMID:24127577

  18. Porphyrin-Based Nanostructures for Photocatalytic Applications

    PubMed Central

    Chen, Yingzhi; Li, Aoxiang; Huang, Zheng-Hong; Wang, Lu-Ning; Kang, Feiyu

    2016-01-01

    Well-defined organic nanostructures with controllable size and morphology are increasingly exploited in optoelectronic devices. As promising building blocks, porphyrins have demonstrated great potentials in visible-light photocatalytic applications, because of their electrical, optical and catalytic properties. From this perspective, we have summarized the recent significant advances on the design and photocatalytic applications of porphyrin-based nanostructures. The rational strategies, such as texture or crystal modification and interfacial heterostructuring, are described. The applications of the porphyrin-based nanostructures in photocatalytic pollutant degradation and hydrogen evolution are presented. Finally, the ongoing challenges and opportunities for the future development of porphyrin nanostructures in high-quality nanodevices are also proposed. PMID:28344308

  19. Spectroscopic characterization of the iron-oxo intermediate in cytochrome P450.

    PubMed

    Jung, Christiane; Schünemann, Volker; Lendzian, Friedhelm; Trautwein, Alfred X; Contzen, Jörg; Galander, Marcus; Böttger, Lars H; Richter, Matthias; Barra, Anne-Laure

    2005-10-01

    From analogy to chloroperoxidase from Caldariomyces fumago, it is believed that the electronic structure of the intermediate iron-oxo species in the catalytic cycle of cytochrome P450 corresponds to an iron(IV) porphyrin-pi-cation radical (compound I). However, our recent studies on P450cam revealed that after 8 ms a tyrosine radical and iron(IV) were formed in the reaction of ferric P450 with external oxidants in the shunt pathway. The present study on the heme domain of P450BM3 (P450BMP) shows a similar result. In addition to a tyrosine radical, a contribution from a tryptophan radical was found in the electron paramagnetic resonance (EPR) spectra of P450BMP. Here we present comparative multi-frequency EPR (9.6, 94 and 285 GHz) and Mössbauer spectroscopic studies on freeze-quenched intermediates produced using peroxy acetic acid as oxidant for both P450 cytochromes. After 8 ms in both systems, amino acid radicals occurred instead of the proposed iron(IV) porphyrin-pi-cation radical, which may be transiently formed on a much faster time scale. These findings are discussed with respect to other heme thiolate proteins. Our studies demonstrate that intramolecular electron transfer from aromatic amino acids is a common feature in these enzymes. The electron transfer quenches the presumably transiently formed porphyrin-pi-cation radical, which makes it extremely difficult to trap compound I.

  20. Halogen lamp experiment, HALEX

    NASA Technical Reports Server (NTRS)

    Schmitt, G.; Stapelmann, J.

    1986-01-01

    The main purpose of the Halogen Lamp Experiment (HALEX) was to investigate the operation of a halogen lamp during an extended period in a microgravity environment and to prove its behavior in space. The Mirror Heating Facilities for Crystal Growth and Material Science Experiments in space relies on one or two halogen lamps as a furnace to melt the specimens. The HALEX aim is to verify: full power operation of a halogen lamp for a period of about 60 hours; achievement of about 10% of its terrestrial life span; and operation of the halogen lamp under conditions similar to furnace operation.

  1. The Halogen Bond

    PubMed Central

    2016-01-01

    The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design. PMID:26812185

  2. Medium Effects are as Important as Catalyst Design for Selectivity in Electrocatalytic Oxygen Reduction by Iron-porphyrin Complexes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rigsby, Matthew L.; Wasylenko, Derek J.; Pegis, Michael L.

    2015-04-08

    Several substituted iron porphyrin com-plexes were evaluated for oxygen reduction reaction (ORR) electrocatalysis in different homogeneous and heterogeneous media. The selectivity for 4-electron re-duction to H2O vs. 2-electron reduction to H2O2 varies substantially from one medium to another for a given catalyst. In many cases, the influence of the medium in which the catalyst is evaluated has a larger effect on the observed selectivity than the factors attributable to chemical modification of the catalyst. For instance, introduction of potential proton relays has variable effects depending on the catalyst medium. Thus, comparisons of ORR selectivity results need to be interpreted withmore » caution, as the catalysis is a property not just of the catalyst, but also of the larger mesoscale environment be-yond the catalyst. Still, in all the direct pairwise comparisons in the same medium, the catalysts with potential proton relays have similar or better selectivity for the preferred 4e– path. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.« less

  3. Urinary porphyrin excretion in neurotypical and autistic children.

    PubMed

    Woods, James S; Armel, Sarah E; Fulton, Denise I; Allen, Jason; Wessels, Kristine; Simmonds, P Lynne; Granpeesheh, Doreen; Mumper, Elizabeth; Bradstreet, J Jeffrey; Echeverria, Diana; Heyer, Nicholas J; Rooney, James P K

    2010-10-01

    Increased urinary concentrations of pentacarboxyl-, precopro- and copro-porphyrins have been associated with prolonged mercury (Hg) exposure in adults, and comparable increases have been attributed to Hg exposure in children with autism (AU). This study was designed to measure and compare urinary porphyrin concentrations in neurotypical (NT) children and same-age children with autism, and to examine the association between porphyrin levels and past or current Hg exposure in children with autism. This exploratory study enrolled 278 children 2-12 years of age. We evaluated three groups: AU, pervasive developmental disorder-not otherwise specified (PDD-NOS), and NT. Mothers/caregivers provided information at enrollment regarding medical, dental, and dietary exposures. Urine samples from all children were acquired for analyses of porphyrin, creatinine, and Hg. Differences between groups for mean porphyrin and Hg levels were evaluated. Logistic regression analysis was conducted to determine whether porphyrin levels were associated with increased risk of autism. Mean urinary porphyrin concentrations are naturally high in young children and decline by as much as 2.5-fold between 2 and 12 years of age. Elevated copro- (p < 0.009), hexacarboxyl- (p < 0.01) and pentacarboxyl- (p < 0.001) porphyrin concentrations were significantly associated with AU but not with PDD-NOS. No differences were found between NT and AU in urinary Hg levels or in past Hg exposure as determined by fish consumption, number of dental amalgam fillings, or vaccines received. These findings identify disordered porphyrin metabolism as a salient characteristic of autism. Hg exposures were comparable between diagnostic groups, and a porphyrin pattern consistent with that seen in Hg-exposed adults was not apparent.

  4. Urinary Porphyrin Excretion in Neurotypical and Autistic Children

    PubMed Central

    Woods, James S.; Armel, Sarah E.; Fulton, Denise I.; Allen, Jason; Wessels, Kristine; Simmonds, P. Lynne; Granpeesheh, Doreen; Mumper, Elizabeth; Bradstreet, J. Jeffrey; Echeverria, Diana; Heyer, Nicholas J.; Rooney, James P.K.

    2010-01-01

    Background Increased urinary concentrations of pentacarboxyl-, precopro- and copro-porphyrins have been associated with prolonged mercury (Hg) exposure in adults, and comparable increases have been attributed to Hg exposure in children with autism (AU). Objectives This study was designed to measure and compare urinary porphyrin concentrations in neurotypical (NT) children and same-age children with autism, and to examine the association between porphyrin levels and past or current Hg exposure in children with autism. Methods This exploratory study enrolled 278 children 2–12 years of age. We evaluated three groups: AU, pervasive developmental disorder-not otherwise specified (PDD-NOS), and NT. Mothers/caregivers provided information at enrollment regarding medical, dental, and dietary exposures. Urine samples from all children were acquired for analyses of porphyrin, creatinine, and Hg. Differences between groups for mean porphyrin and Hg levels were evaluated. Logistic regression analysis was conducted to determine whether porphyrin levels were associated with increased risk of autism. Results Mean urinary porphyrin concentrations are naturally high in young children and decline by as much as 2.5-fold between 2 and 12 years of age. Elevated copro- (p < 0.009), hexacarboxyl- (p < 0.01) and pentacarboxyl- (p < 0.001) porphyrin concentrations were significantly associated with AU but not with PDD-NOS. No differences were found between NT and AU in urinary Hg levels or in past Hg exposure as determined by fish consumption, number of dental amalgam fillings, or vaccines received. Conclusions These findings identify disordered porphyrin metabolism as a salient characteristic of autism. Hg exposures were comparable between diagnostic groups, and a porphyrin pattern consistent with that seen in Hg-exposed adults was not apparent. PMID:20576582

  5. Photoinduced oxidation of a water-soluble manganese(III) porphyrin

    PubMed Central

    Maliyackel, Anthony C.; Otvos, John W.; Spreer, Larry O.; Calvin, Melvin

    1986-01-01

    The photoinduced oxidation of tetra(N-methyl-4-pyridyl)porphyrinmanganese(III) has been achieved in homogeneous solution. The manganese porphyrin was used as an electron donor in a three-component system with tris-(2,2′-bipyridine)ruthenium(II) as the photosensitizer and chloropentaamminecobalt(III) as the electron acceptor. The photooxidized manganese porphyrin is unstable in aqueous solution, reverting to the starting manganese(III) porphyrin. The oxidation of manganese(III) porphyrin and the subsequent reduction of the oxidized porphyrin can be cycled repeatedly. PMID:16593699

  6. Iron in Parkinson disease, blood diseases, malaria and ferritin

    NASA Astrophysics Data System (ADS)

    Bauminger, E. R.; Nowik, I.

    1998-12-01

    The concentration of iron in Substantia nigra, the part of the brain which is involved in Parkinson disease, has been found by Mössbauer spectroscopy (MS) to be ~ 160 μg/g wet tissue and ~ 670 μg/g dry weight, both in control and Parkinson samples. All the iron observed by MS in these samples is ferritin-like iron. In several blood diseases, large amounts of ferritin-like iron have been observed in red blood cells. Desferral removed iron from serum, but not from red blood cells. The iron compound in the malarial pigment of human blood infected by P. falciparum was found to be hemin-like, whereas the pigment iron in rats infected by P. berghei was different from any known iron porphyrin.

  7. Halogenation of microcapsule walls

    NASA Technical Reports Server (NTRS)

    Davis, T. R.; Schaab, C. K.; Scott, J. C.

    1972-01-01

    Procedure for halogenation of confining walls of both gelatin and gelatin-phenolic resin capsules is similar to that used for microencapsulation. Ten percent halogen content renders capsule wall nonburning; any higher content enhances flame-retardant properties of selected internal phase material. Halogenation decreases permeability of wall material to encapsulated materials.

  8. Nickel porphyrins for memory optical applications

    DOEpatents

    Shelnutt, John A.; Jia, Songling; Medforth, Craig; Holten, Dewey; Nelson, Nora Y.; Smith, Kevin M.

    2000-01-01

    The present invention relates to a nickel-porphyrin derivative in a matrix, the nickel-porphyrin derivative comprising at least two conformational isomers, a lower-energy-state conformer and a higher-energy-state conformer, such that when the higher-energy-state conformer is generated from the lower-energy-state conformer following absorption of a photon of suitable energy, the time to return to the lower-energy-state conformer is greater than 40 nanoseconds at approximately room temperature. The nickel-porphyrin derivative is useful in optical memory applications.

  9. In Silico Study, Synthesis, and Cytotoxic Activities of Porphyrin Derivatives

    PubMed Central

    Kurniawan, Fransiska; Miura, Youhei; Kartasasmita, Rahmana Emran; Mutalib, Abdul

    2018-01-01

    Five known porphyrins, 5,10,15,20-tetrakis(p-tolyl)porphyrin (TTP), 5,10,15,20-tetrakis(p-bromophenyl)porphyrin (TBrPP), 5,10,15,20-tetrakis(p-aminophenyl)porphyrin (TAPP), 5,10,15-tris(tolyl)-20-mono(p-nitrophenyl)porphyrin (TrTMNP), 5,10,15-tris(tolyl)-20-mono(p-aminophenyl)porphyrin (TrTMAP), and three novel porphyrin derivatives, 5,15-di-[bis(3,4-ethylcarboxymethylenoxy)phenyl]-10,20-di(p-tolyl)porphyrin (DBECPDTP), 5,10-di-[bis(3,4-ethylcarboxymethylenoxy)phenyl]-15,20-di-(methylpyrazole-4-yl)porphyrin (cDBECPDPzP), 5,15-di-[bis(3,4-ethylcarboxymethylenoxy)phenyl]-10,20-di-(methylpyrazole-4-yl)porphyrin (DBECPDPzP), were used to study their interaction with protein targets (in silico study), and were synthesized. Their cytotoxic activities against cancer cell lines were tested using 3-(4,5-dimetiltiazol-2-il)-2,5-difeniltetrazolium bromide (MTT) assay. The interaction of porphyrin derivatives with carbonic anhydrase IX (CAIX) and REV-ERBβ proteins were studied by molecular docking and molecular dynamic simulation. In silico study results reveal that DBECPDPzP and TrTMNP showed the highest binding interaction with REV- ERBβ and CAIX, respectively, and both complexes of DBECPDPzP-REV-ERBβ and TrTMNP-CAIX showed good and comparable stability during molecular dynamic simulation. The studied porphyrins have selective growth inhibition activities against tested cancer cells and are categorized as marginally active compounds based on their IC50. PMID:29361701

  10. Photoconductivity in DNA-Porphyrin Complexes

    NASA Astrophysics Data System (ADS)

    Myint, Peco; Oxford, Emma; Nyazenga, Collence; Smith, Walter; Qi, Zhengqing; Johnson, A. T.

    2015-03-01

    We have measured the photoconductivity of λ - DNA that is modified by intercalating a porphyrin compound, meso-tetrakis(N-methyl-4-pyridiniumyl)porphyrin (TMPyP), into its base stacks. Intercalation was verified by a red shift and hypochromism of the Soret absorption peak. The DNA/porphyrin strands were then deposited onto oxidized silicon substrates which had been patterned with interdigitated electrodes, and blown dry. Electrical measurements were carried out under nitrogen, using illumination from a 445 nm laser; this wavelength falls within the absorption peak of the DNA/porphyrin complexes. When initially measured under dry nitrogen, the complexes show no photoconductivity or dark conductivity. However, at relative humidities of 30% and above, we do observe dark conductivity, and also photoconductivity that grows with time. Photoconductivity gets larger at higher relative humidity. Remarkably, when the humidity is lowered again, some photoconductivity is now observed, indicating a change that persists for more than 24 hours. It may be that the humidity alters the structure of the DNA, perhaps allowing for better alignment of the bases. This work was supported by NSF Grant BMAT-1306170.

  11. Differential interaction of porphyrins used in photoradiation therapy with ferrochelatase.

    PubMed Central

    Dailey, H A; Smith, A

    1984-01-01

    The mechanism of porphyrin accumulation by tumours is not yet established. If metabolism aids porphyrin elimination, tumours, unlike normal tissues, may not metabolize porphyrins used clinically, such as proto-, haemato-, OO'-diacetyl-haemato- and monohydroxyethyl-monovinyl-deutero-porphyrin. Proto-, haemato- and monohydroxyethyl-monovinyl-deutero-porphyrin are substrates for the mitochondrial enzyme ferrochelatase (EC 4.99.1.1), which can form haem analogues from exogenous porphyrins. The Km values for proto-, haemato- and monohydroxyethyl-monovinyl-deutero-porphyrin are 11, 22 and 23 microM respectively. However, OO'-diacetyl-haematoporphyrin is an effective competitive inhibitor with Ki of 11 microM. Hepatic ferrochelatase specific activity is 5.9 and 5.5 nmol of haem/h per mg of protein respectively in normal Buffalo rat and in those bearing the extrahepatic Morris 7288C hepatoma, and is only 0.13 nmol/h per mg in the hepatomas. Therefore low ferrochelatase activity in cancerous cells may provide one means whereby some porphyrins accumulate in tumours, and the ability of certain porphyrins to act as ferrochelatase inhibitors may provide another. PMID:6497856

  12. Direct protein photoinduced conformational changes using porphyrins.

    NASA Astrophysics Data System (ADS)

    Brancaleon, Lorenzo; Silva, Ivan; Fernandez, Nicholas; Johnson, Eric; Sansone, Samuel

    2008-03-01

    Most proteins functions depend on the interaction with other ligands. These interactions depend on uniquely structured binding sites formed by the folding of the proteins. Ligands can often prompt intended as well as ``accidental'' protein structural changes. One can foresee that the ability to prompt and control post-translational protein folding could be a powerful tool to investigate protein folding mechanisms but also to inhibit certain proteins or induce new properties to proteins. One possible way to produce such structural disruption is the combination of light and photoactive ligands. This option has been investigated in recent years by exploiting photoisomerization and other properties of non-physiological dyes. We used an alternative approach which uses porphyrins as the ``triggers'' of structural changes. The advantage of porphyrins is that they can be found naturally in living cells. The photophysical properties of porphyrins can induce local as well as long range effects on the structure of the bound protein. Porphyrins are known to produce structural changes in porphyrin-specific proteins, however the novelty of our results is that we demonstrated that these dyes can also produce structural changes in non-porphyrin-specific globular proteins. We will present an overview of our research to-date in this field and its potential applications.

  13. A Six-Coordinate Peroxynitrite Low-Spin Iron(III) Porphyrinate Complex—The Product of the Reaction of Nitrogen Monoxide (·NO (g)) with a Ferric-Superoxide Species

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sharma, Savita K.; Schaefer, Andrew W.; Lim, Hyeongtaek

    Peroxynitrite ( –OON=O, PN) is a reactive nitrogen species (RNS) which can effect deleterious nitrative or oxidative (bio)chemistry. It may derive from reaction of superoxide anion (O 2 •–) with nitric oxide (·NO) and has been suggested to form an as-yet unobserved bound heme-iron-PN intermediate in the catalytic cycle of nitric oxide dioxygenase (NOD) enzymes, which facilitate a ·NO homeostatic process, i.e., its oxidation to the nitrate anion. Here, a discrete six-coordinate low-spin porphyrinate-Fe III complex [(P Im)Fe III( –OON=O)] (P Im; a porphyrin moiety with a covalently tethered imidazole axial “base” donor ligand) has been identified and characterized bymore » various spectroscopies (UV–vis, NMR, EPR, XAS, resonance Raman) and DFT calculations, following its formation at –80 °C by addition of ·NO (g) to the heme-superoxo species, [(P Im)Fe III(O 2 •–)]. DFT calculations confirm that is a six-coordinate low-spin species with the PN ligand coordinated to iron via its terminal peroxidic anionic O atom with the overall geometry being in a cis-configuration. Complex thermally transforms to its isomeric low-spin nitrato form [(P Im)Fe III(NO 3 –)]. While previous (bio)chemical studies show that phenolic substrates undergo nitration in the presence of PN or PN-metal complexes, in the present system, addition of 2,4-di- tert-butylphenol ( 2,4DTBP) to complex does not lead to nitrated phenol; the nitrate complex still forms. Furthermore, DFT calculations reveal that the phenolic H atom approaches the terminal PN O atom (farthest from the metal center and ring core), effecting O–O cleavage, giving nitrogen dioxide (·NO 2) plus a ferryl compound [(P Im)Fe IV=O] (7); this rebounds to give [(P Im)Fe III(NO 3 –)].The generation and characterization of the long sought after ferriheme peroxynitrite complex has been accomplished.« less

  14. A Six-Coordinate Peroxynitrite Low-Spin Iron(III) Porphyrinate Complex—The Product of the Reaction of Nitrogen Monoxide (·NO (g)) with a Ferric-Superoxide Species

    DOE PAGES

    Sharma, Savita K.; Schaefer, Andrew W.; Lim, Hyeongtaek; ...

    2017-11-01

    Peroxynitrite ( –OON=O, PN) is a reactive nitrogen species (RNS) which can effect deleterious nitrative or oxidative (bio)chemistry. It may derive from reaction of superoxide anion (O 2 •–) with nitric oxide (·NO) and has been suggested to form an as-yet unobserved bound heme-iron-PN intermediate in the catalytic cycle of nitric oxide dioxygenase (NOD) enzymes, which facilitate a ·NO homeostatic process, i.e., its oxidation to the nitrate anion. Here, a discrete six-coordinate low-spin porphyrinate-Fe III complex [(P Im)Fe III( –OON=O)] (P Im; a porphyrin moiety with a covalently tethered imidazole axial “base” donor ligand) has been identified and characterized bymore » various spectroscopies (UV–vis, NMR, EPR, XAS, resonance Raman) and DFT calculations, following its formation at –80 °C by addition of ·NO (g) to the heme-superoxo species, [(P Im)Fe III(O 2 •–)]. DFT calculations confirm that is a six-coordinate low-spin species with the PN ligand coordinated to iron via its terminal peroxidic anionic O atom with the overall geometry being in a cis-configuration. Complex thermally transforms to its isomeric low-spin nitrato form [(P Im)Fe III(NO 3 –)]. While previous (bio)chemical studies show that phenolic substrates undergo nitration in the presence of PN or PN-metal complexes, in the present system, addition of 2,4-di- tert-butylphenol ( 2,4DTBP) to complex does not lead to nitrated phenol; the nitrate complex still forms. Furthermore, DFT calculations reveal that the phenolic H atom approaches the terminal PN O atom (farthest from the metal center and ring core), effecting O–O cleavage, giving nitrogen dioxide (·NO 2) plus a ferryl compound [(P Im)Fe IV=O] (7); this rebounds to give [(P Im)Fe III(NO 3 –)].The generation and characterization of the long sought after ferriheme peroxynitrite complex has been accomplished.« less

  15. Porphyrin Tests

    MedlinePlus

    ... variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason ... healthcare practitioner's office? No. Porphyrin tests require specialized equipment and technical skills. Some tests may be performed ...

  16. Metalloporphyrins and their uses as imageable tumor-targeting agents for radiation therapy

    DOEpatents

    Miura, Michiko; Slatkin, Daniel N.

    2003-05-20

    The present invention covers halogenated derivatives of boronated porphyrins containing multiple carborane cages having the formula ##STR1## which selectively accumulate in neoplastic tissue within the irradiation volume and thus can be used in cancer therapies including, but not limited to, boron neutron- capture therapy and photodynamic therapy. The present invention also covers methods for using these halogenated derivatives of boronated porphyrins in tumor imaging and cancer treatment.

  17. [Disorder of porphyrin metabolism in thallium intoxication (author's transl)].

    PubMed

    Graben, N; Doss, M; Klöppel, H A

    1978-08-04

    A 19-year old male ingested in suicidal attempt 750 mg of thallium. He developed the characteristic symptoms of thallium intoxication. During the acute phase the urinary excretion of porphyrins and porphyrin precursors was largely increased. The percentage distribution of the individual metabolites of heme synthesis revealed a preponderance of kopro- and uroporphyrin. This constellation (kopro- greater than uro- greater than tricarboxylic porphyrin) differs appreciably from that one in lead intoxication. The observation of increased urinary excretion of porphyrins and their precursors in a possibly particular spectrum in thallium intoxication is of special interest for differential-diagnostic reasoning. In each case of a toxic disorder of porphyrin metabolism thallium intoxication ought to be considered a possible cause.

  18. HAEM SYNTHASE AND COBALT PORPHYRIN SYNTHASE IN VARIOUS MICRO-ORGANISMS.

    PubMed

    PORRA, R J; ROSS, B D

    1965-03-01

    1. The preparation of a crude extract of Clostridium tetanomorphum containing cobalt porphyrin synthase but little haem-synthase activity is described. 2. The properties of cobalt porphyrin synthase in the clostridial extracts is compared with the properties of a haem synthase present in crude extracts of the yeast Torulopsis utilis. 3. Cobalt porphyrin synthase in extracts of C. tetanomorphum inserts Co(2+) ions into the following dicarboxylic porphyrins in descending order of rate of insertion: meso-, deutero- and proto-porphyrins. Esterification renders meso- and deutero-porphyrins inactive as substrates. Neither the tetracarboxylic (coproporphyrin III) nor the octacarboxylic (uroporphyrin III) compounds are converted into cobalt porphyrins by the extract, but the non-enzymic incorporation of Co(2+) ions into these two porphyrins is rapid. These extracts are unable to insert Mn(2+), Zn(2+), Mg(2+) or Cu(2+) ions into mesoporphyrin. 4. Crude extracts of T. utilis readily insert both Co(2+) and Fe(2+) ions into deutero-, meso, and proto-porphyrins. Unlike the extracts of C. tetanomorphum, these preparations catalyse the insertion of Co(2+) ions into deuteroporphyrin more rapidly than into mesoporphyrin. This parallels the formation of haems by the T. utilis extract. 5. Cobalt porphyrin synthase is present in the particulate fraction of the extracts of C. tetanomorphum but requires a heat-stable factor present in the soluble fraction. This soluble factor can be replaced by GSH. 6. Cobalt porphyrin synthase in the clostridial extract is inhibited by iodoacetamide and to a smaller extent by p-chloromercuribenzoate and N-ethylmaleimide. The haem synthases of T. utilis and Micrococcus denitrificans are also inhibited by various thiol reagents.

  19. Is halogen content the most important factor in the removal of halogenated trace organics by MBR treatment?

    PubMed

    Hai, Faisal I; Tadkaew, Nichanan; McDonald, James A; Khan, Stuart J; Nghiem, Long D

    2011-05-01

    This study investigated the relationship between physicochemical properties (namely halogen content and hydrophobicity) of halogenated trace organics and their removal efficiencies by a laboratory scale membrane bioreactor (MBR) under stable operating conditions. The reported results demonstrated a combined effect of halogen content and hydrophobicity on the removal. Compounds with high halogen content (>0.3) were well removed (>85%) when they possessed high hydrophobicity (Log D>3.2), while those with lower Log D values were also well removed if they had low halogen content (<0.1). General indices such as the BIOWIN index (which is based on only biodegradation) or a more specific index such as the halogen content (which captures a chemical aspect) appeared insufficient to predict the removal efficiency of halogenated compounds in MBR. Experimental data confirmed that the ratio of halogen content and Log D, which incorporates two important physico-chemical properties, is comparatively more suitable. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. Spectroscopic and Kinetic Characterization of Peroxidase-Like π-Cation Radical Pinch-Porphyrin-Iron(III) Reaction Intermediate Models of Peroxidase Enzymes.

    PubMed

    Hernández Anzaldo, Samuel; Arroyo Abad, Uriel; León García, Armando; Ramírez Rosales, Daniel; Zamorano Ulloa, Rafael; Reyes Ortega, Yasmi

    2016-06-27

    The spectroscopic and kinetic characterization of two intermediates from the H₂O₂ oxidation of three dimethyl ester [(proto), (meso), (deuteroporphyrinato) (picdien)]Fe(III) complexes ([FePPPic], [FeMPPic] and [FeDPPic], respectively) pinch-porphyrin peroxidase enzyme models, with s = 5/2 and 3/2 Fe(III) quantum mixed spin (qms) ground states is described herein. The kinetic study by UV/Vis at λmax = 465 nm showed two different types of kinetics during the oxidation process in the guaiacol test for peroxidases (1-3 + guaiacol + H₂O₂ → oxidation guaiacol products). The first intermediate was observed during the first 24 s of the reaction. When the reaction conditions were changed to higher concentration of pinch-porphyrins and hydrogen peroxide only one type of kinetics was observed. Next, the reaction was performed only between pinch-porphyrins-Fe(III) and H₂O₂, resulting in only two types of kinetics that were developed during the first 0-4 s. After this time a self-oxidation process was observed. Our hypotheses state that the formation of the π-cation radicals, reaction intermediates of the pinch-porphyrin-Fe(III) family with the ligand picdien [N,N'-bis-pyridin-2-ylmethyl-propane-1,3-diamine], occurred with unique kinetics that are different from the overall process and was involved in the oxidation pathway. UV-Vis, ¹H-NMR and ESR spectra confirmed the formation of such intermediates. The results in this paper highlight the link between different spectroscopic techniques that positively depict the kinetic traits of artificial compounds with enzyme-like activity.

  1. Porphyrins blood test

    MedlinePlus

    Chernecky CC, Berger BJ. Porphyrins, quantitative - blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures . 6th ed. Philadelphia, PA: Elsevier Saunders; 2013:891-892. ...

  2. A Single Crystalline Porphyrinic Titanium MetalOrganic Framework

    DTIC Science & Technology

    2015-04-28

    22, which was synthesized from preformed titanium -oxo carboxylate clusters and porphyrinic ligands. PCN-22 possesses high porosity and photocatalytic...DOI: 10.1039/c5sc00916b www.rsc.org/chemicalscience 3926 | Chem. Sci., 2015, 6, 3926–3930e porphyrinic titanium metal– organic framework† Shuai Yuan...Scott J. Dalgarnoc and Hong-Cai Zhou*a We successfully assembled the photocatalytic titanium -oxo cluster and photosensitizing porphyrinic linker into a

  3. Hydrocarbon oxidation by beta-halogenated dioxoruthenium(VI) porphyrin complexes: effect of reduction potential (RuVI/V) and C-H bond-dissociation energy on rate constants.

    PubMed

    Che, Chi-Ming; Zhang, Jun-Long; Zhang, Rui; Huang, Jie-Sheng; Lai, Tat-Shing; Tsui, Wai-Man; Zhou, Xiang-Ge; Zhou, Zhong-Yuan; Zhu, Nianyong; Chang, Chi Kwong

    2005-11-18

    beta-Halogenated dioxoruthenium(VI) porphyrin complexes [Ru(VI)(F(28)-tpp)O(2)] [F(28)-tpp=2,3,7,8,12,13, 17,18-octafluoro-5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato(2-)] and [Ru(VI)(beta-Br(8)-tmp)O(2)] [beta-Br(8)-tmp=2,3,7,8,12,13,17,18-octabromo-5,10,15,20- tetrakis(2,4,6-trimethylphenyl)porphyrinato(2-)] were prepared from reactions of [Ru(II)(por)(CO)] [por=porphyrinato(2-)] with m-chloroperoxybenzoic acid in CH(2)Cl(2). Reactions of [Ru(VI)(por)O(2)] with excess PPh(3) in CH(2)Cl(2) gave [Ru(II)(F(20)-tpp)(PPh(3))(2)] [F(20)-tpp=5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato(2-)] and [Ru(II)(F(28)-tpp)(PPh(3))(2)]. The structures of [Ru(II)(por)(CO)(H(2)O)] and [Ru(II)(por)(PPh(3))(2)] (por=F(20)-tpp, F(28)-tpp) were determined by X-ray crystallography, revealing the effect of beta-fluorination of the porphyrin ligand on the coordination of axial ligands to ruthenium atom. The X-ray crystal structure of [Ru(VI)(F(20)-tpp)O(2)] shows a Ru=O bond length of 1.718(3) A. Electrochemical reduction of [Ru(VI)(por)O(2)] (Ru(VI) to Ru(V)) is irreversible or quasi-reversible, with the E(p,c)(Ru(VI/V)) spanning -0.31 to -1.15 V versus Cp(2)Fe(+/0). Kinetic studies were performed for the reactions of various [Ru(VI)(por)O(2)], including [Ru(VI)(F(28)-tpp)O(2)] and [Ru(VI)(beta-Br(8)-tmp)O(2)], with para-substituted styrenes p-X-C(6)H(4)CH=CH(2) (X=H, F, Cl, Me, MeO), cis- and trans-beta-methylstyrene, cyclohexene, norbornene, ethylbenzene, cumene, 9,10-dihydroanthracene, xanthene, and fluorene. The second-order rate constants (k(2)) obtained for the hydrocarbon oxidations by [Ru(VI)(F(28)-tpp)O(2)] are up to 28-fold larger than by [Ru(VI)(F(20)-tpp)O(2)]. Dual-parameter Hammett correlation implies that the styrene oxidation by [Ru(VI)(F(28)-tpp)O(2)] should involve rate-limiting generation of a benzylic radical intermediate, and the spin delocalization effect is more important than the polar effect. The k(2) values for the oxidation of styrene and

  4. Single-step electron transfer on the nanometer scale: ultra-fast charge shift in strongly coupled zinc porphyrin-gold porphyrin dyads.

    PubMed

    Fortage, Jérôme; Boixel, Julien; Blart, Errol; Hammarström, Leif; Becker, Hans Christian; Odobel, Fabrice

    2008-01-01

    The synthesis, electrochemical properties, and photoinduced electron transfer processes of a series of three novel zinc(II)-gold(III) bisporphyrin dyads (ZnP--S--AuP(+)) are described. The systems studied consist of two trisaryl porphyrins connected directly in the meso position via an alkyne unit to tert-(phenylenethynylene) or penta(phenylenethynylene) spacers. In these dyads, the estimated center to center interporphyrin separation distance varies from 32 to 45 A. The absorption, emission, and electrochemical data indicate that there are strong electronic interactions between the linked elements, thanks to the direct attachment of the spacer on the porphyrin ring through the alkyne unit. At room temperature in toluene, light excitation of the zinc porphyrin results in almost quantitative formation of the charge shifted state (.+)ZnP--S--AuP(.), whose lifetime is in the order of hundreds of picoseconds. In this solvent, the charge-separated state decays to the ground state through the intermediate population of the zinc porphyrin triplet excited state. Excitation of the gold porphyrin leads instead to rapid energy transfer to the triplet ZnP. In dichloromethane the charge shift reactions are even faster, with time constants down to 2 ps, and may be induced also by excitation of the gold porphyrin. In this latter solvent, the longest charge-shifted lifetime (tau=2.3 ns) was obtained with the penta-(phenylenethynylene) spacer. The charge shift reactions are discussed in terms of bridge-mediated super-exchange mechanisms as electron or hole transfer. These new bis-porphyrin arrays, with strong electronic coupling, represent interesting molecular systems in which extremely fast and efficient long-range photoinduced charge shift occurs over a long distance. The rate constants are two to three orders of magnitude larger than for corresponding ZnP--AuP(+) dyads linked via meso-phenyl groups to oligo-phenyleneethynylene spacers. This study demonstrates the critical

  5. Dissociative Photoionization of 1-Halogenated Silacyclohexanes: Silicon Traps the Halogen.

    PubMed

    Bodi, Andras; Sigurdardottir, Katrin Lilja; Kvaran, Ágúst; Bjornsson, Ragnar; Arnason, Ingvar

    2016-11-23

    The threshold photoelectron spectra and threshold photoionization mass spectra of 1-halogenated-1-silacyclohexanes, for the halogens X = F, Cl, Br, and I, have been obtained using synchrotron vacuum ultraviolet radiation and photoelectron photoion coincidence spectroscopy. As confirmed by a similar ionization onset and density functional theory molecular orbitals, the ionization to the ground state is dominated by electron removal from the silacyclohexane ring for X = F, Cl, and Br, and from the halogen lone pair for X = I. The breakdown diagrams show that the dissociative photoionization mechanism is also different for X = I. Whereas the parent ions decay by ethylene loss for X = F to Br in the low-energy regime, the iodine atom is lost for X = I. The first step is followed by a sequential ethylene loss at higher internal energies in each of the compounds. It is argued that the tendency of silicon to lower bond angles stabilizes the complex cation in which C 2 H 4 is η 2 -coordinated to it, and which precedes ethylene loss. Together with the relatively strong silicon-halogen bonds and the increased inductive effect of the silacyclohexane ring in stabilizing the cation, this explains the main differences observed in the fragmentation of the halogenated silacyclohexane and halogenated cyclohexane ions. The breakdown diagrams have been modeled taking into account slow dissociations at threshold and the resulting kinetic shift. The 0 K appearance energies have been obtained to within 0.08 eV for the ethylene loss for X = F to Br (10.56, 10.51, and 10.51 eV, respectively), the iodine atom loss for X = I (10.11 eV), the sequential ethylene loss for X = F to I (12.29, 12.01, 11.94, and 11.86 eV, respectively), and the minor channels of H loss for X = F (10.56 eV) and propylene loss in X = Cl (also at 10.56 eV). The appearance energies for the major channels likely correspond to the dissociative photoionization reaction energy.

  6. Boiling points of halogenated ethanes: an explanatory model implicating weak intermolecular hydrogen-halogen bonding.

    PubMed

    Beauchamp, Guy

    2008-10-23

    This study explores via structural clues the influence of weak intermolecular hydrogen-halogen bonds on the boiling point of halogenated ethanes. The plot of boiling points of 86 halogenated ethanes versus the molar refraction (linked to polarizability) reveals a series of straight lines, each corresponding to one of nine possible arrangements of hydrogen and halogen atoms on the two-carbon skeleton. A multiple linear regression model of the boiling points could be designed based on molar refraction and subgroup structure as independent variables (R(2) = 0.995, standard error of boiling point 4.2 degrees C). The model is discussed in view of the fact that molar refraction can account for approximately 83.0% of the observed variation in boiling point, while 16.5% could be ascribed to weak C-X...H-C intermolecular interactions. The difference in the observed boiling point of molecules having similar molar refraction values but differing in hydrogen-halogen intermolecular bonds can reach as much as 90 degrees C.

  7. Preparation of porphyrins and their metal complexes

    DOEpatents

    Ellis, Jr., Paul E.; Langdale, Wayne A.

    1997-01-01

    A hydroxyl-containing pyrrolic compound having a hydroxyl group or a hydroxyl-containing group in the 2-position, optionally substituted in the beta positions, is condensed in an acidified two immiscible phase solvent system to produce excellent yields of the corresponding porphyrin or metal porphyrin.

  8. Preparation of porphyrins and their metal complexes

    DOEpatents

    Ellis, P.E. Jr.; Langdale, W.A.

    1997-08-19

    A hydroxyl-containing pyrrolic compound having a hydroxyl group or a hydroxyl-containing group in the 2-position, optionally substituted in the beta positions, is condensed in an acidified two immiscible phase solvent system to produce excellent yields of the corresponding porphyrin or metal porphyrin.

  9. Halogen Chemistry in the CMAQ Model

    EPA Science Inventory

    Halogens (iodine and bromine) emitted from oceans alter atmospheric chemistry and influence atmospheric ozone mixing ratio. We previously incorporated a representation of detailed halogen chemistry and emissions of organic and inorganic halogen species into the hemispheric Commun...

  10. Excitation energy migration processes in various multi-porphyrin assemblies.

    PubMed

    Yang, Jaesung; Kim, Dongho

    2012-08-13

    The electronic interactions and excitation energy transfer (EET) processes of a variety of multi-porphyrin arrays with linear, cyclic and box architectures have been explored. Directly meso-meso linked linear arrays (Z(N)) exhibit strong excitonic coupling with an exciton coherence length of approximately 6 porphyrin units, while fused linear arrays (T(N)) exhibit extensive π-conjugation over the whole array. The excitonic coherence length in directly linked cyclic porphyrin rings (CZ(N)) was determined to be approximately 2.7 porphyrin units by simultaneous analysis of fluorescence intensities and lifetimes at the single-molecule level. By performing transient absorption (TA) and TA anisotropy decay measurements, the EET rates in m-phenylene linked cyclic porphyrin wheels C12ZA and C24ZB were determined to be 4 and 36 ps(-1), respectively. With increasing the size of C(N)ZA, the EET efficiencies decrease owing to the structural distortions that produce considerable non-radiative decay pathways. Finally, the EET rates of self-assembled porphyrin boxes consisting of directly linked diporphyrins, B1A, B2A and B3A, are 48, 98 and 361 ps(-1), respectively. The EET rates of porphyrin boxes consisting of alkynylene-bridged diporphyrins, B2B and B4B, depend on the conformation of building blocks (planar or orthogonal) rather than the length of alkynylene linkers.

  11. Photochemical electron transfer in chlorophyll-porphyrin-quinone triads. The role of the porphyrin-bridging molecule

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Johnson, D.G.; Niemczyk, M.P.; Minsek, D.W.

    1993-06-30

    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,more » 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

  12. Porphyrin framework solids. Synthesis and structure of hybrid coordination polymers of tetra(carboxyphenyl)porphyrins and lanthanide-bridging ions.

    PubMed

    Muniappan, Sankar; Lipstman, Sophia; George, Sumod; Goldberg, Israel

    2007-07-09

    New types of porphyrin-based framework solids were constructed by reacting meso-tetra(3-carboxyphenyl)porphyrin and meso-tetra(4-carboxyphenyl)metalloporphyrins with common salts of lanthanide metal ions. The large size, high coordination numbers and strong affinity for oxo ligands of the latter, combined with favorable hydrothermal reaction conditions, allowed the formation of open three-dimensional single-framework architectures by coordination polymerization, in which the tetradentate porphyrin units are intercoordinated by multinuclear assemblies of the bridging metal ions. The latter serve as construction pillars of the supramolecular arrays, affording stable structures. Several modes of coordination polymerization were revealed by single-crystal X-ray diffraction. They differ by the spatial functionality of the porphyrin building blocks, the coordination patterns of the lanthanide-carboxylate assemblies, and the topology of the resulting frameworks. The seven new reported structures exhibit periodically spaced 0.4-0.6 nm wide channel voids that perforate the respective crystalline polymeric architectures and are accessible to solvent components. Materials based on the m-carboxyphenyl derivative reveal smaller channels than those based on the p-carboxyphenyl analogues. An additional complex of the former with a smaller third-row transition metal (Co) is characterized by coordination connectivity in two dimensions only. Thermal and powder-diffraction analyses confirm the stability of the lanthanide-TmCPP (TmCPP=tetra(m-carboxyphenyl)porphyrin) frameworks.

  13. Evidence for Interfacial Halogen Bonding.

    PubMed

    Swords, Wesley B; Simon, Sarah J C; Parlane, Fraser G L; Dean, Rebecca K; Kellett, Cameron W; Hu, Ke; Meyer, Gerald J; Berlinguette, Curtis P

    2016-05-10

    A homologous series of donor-π-acceptor dyes was synthesized, differing only in the identity of the halogen substituents about the triphenylamine (TPA; donor) portion of each molecule. Each Dye-X (X=F, Cl, Br, and I) was immobilized on a TiO2 surface to investigate how the halogen substituents affect the reaction between the light-induced charge-separated state, TiO2 (e(-) )/Dye-X(+) , with iodide in solution. Transient absorption spectroscopy showed progressively faster reactivity towards nucleophilic iodide with more polarizable halogen substituents: Dye-F < Dye-Cl < Dye-Br < Dye-I. Given that all other structural and electronic properties for the series are held at parity, with the exception of an increasingly larger electropositive σ-hole on the heavier halogens, the differences in dye regeneration kinetics for Dye-Cl, Dye-Br, and Dye-I are ascribed to the extent of halogen bonding with the nucleophilic solution species. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Tropospheric Halogen Chemistry

    NASA Astrophysics Data System (ADS)

    von Glasow, R.; Crutzen, P. J.

    2003-12-01

    Halogens are very reactive chemicals that are known to play an important role in anthropogenic stratospheric ozone depletion chemistry, first recognized by Molina and Rowland (1974). However, they also affect the chemistry of the troposphere. They are of special interest because they are involved in many reaction cycles that can affect the oxidation power of the atmosphere indirectly by influencing the main oxidants O3 and its photolysis product OH and directly, e.g., by reactions of the Cl radical with hydrocarbons (e.g., CH4).Already by the middle of the nineteenth century, Marchand (1852) reported the presence of bromine and iodine in rain and other natural waters. He also mentions the benefits of iodine in drinking water through the prevention of goitres and cretinism. In a prophetic monograph "Air and Rain: The Beginnings of a Chemical Climatology," Smith (1872) describes measurements of chloride in rain water, which he states to originate partly from the oceans by a process that he compares with the bursting of "soap bubbles" which produces "small vehicles" that transfer small spray droplets of seawater to the air. From deviations of the sulfate-to-chloride ratio in coastal rain compared to seawater, Smith concluded that chemical processes occur once the particles are airborne.For almost a century thereafter, however, atmospheric halogens received little attention. One exception was the work by Cauer (1939), who reported that iodine pollution has been significant in Western and Central Europe due to the inefficient burning of seaweed, causing mean gas phase atmospheric concentrations as high as or greater than 0.5 μg m-3. In his classical textbook Air Chemistry and Radioactivity, Junge (1963) devoted less than three pages to halogen gas phase chemistry, discussing chlorine and iodine. As reviewed by Eriksson (1959a, b), the main atmospheric source of halogens is sea salt, derived from the bursting of bubbles of air which are produced by ocean waves and other

  15. Halogenated solvent remediation

    DOEpatents

    Sorenson, Jr., Kent S.

    2008-11-11

    Methods for enhancing bioremediation of ground water contaminated with nonaqueous halogenated solvents are disclosed. An illustrative method includes adding an electron donor for microbe-mediated anaerobic reductive dehalogenation of the halogenated solvents, which electron donor enhances mass transfer of the halogenated solvents from residual source areas into the aqueous phase of the ground water. Illustrative electron donors include C.sub.2-C.sub.4 carboxylic acids and hydroxy acids, salts thereof, esters of C.sub.2-C.sub.4 carboxylic acids and hydroxy acids, and mixtures thereof, of which lactic acid, salts of lactic acid--such as sodium lactate, lactate esters, and mixtures thereof are particularly illustrative. The microbes are either indigenous to the ground water, or such microbes can be added to the ground water in addition to the electron donor.

  16. Mn-porphyrin derivatives as an antioxidant for medical devices.

    PubMed

    Ohse, T; Kawakami, H; Morita, A; Nagaoka, S

    1999-01-01

    It is well known that reactive oxygen species such as O*2- and H2O2 induce the biodegradation or cracking of medical devices in vivo or that they are released from inflammatory cells activated by devices to oxidize low-density lipoprotein. Therefore, the development of a novel antioxidant is required to eliminate the reactive oxygen species. In this paper, we report that Mn-porphyrin derivatives containing a macromolecular Mn-porphyrin are relatively stable compounds that can eliminate O*2- and/or H2O2. The dismutation of O*2- in the porphyrins was determined using a cytochrome c-assay by the xanthine/xanthine oxidase system and using the stopped-flow kinetic analysis technique. The possibility of porphyrins as scavengers of H2O2 was evaluated by in situ measurement with a Clark electrode. As a result, it has been found that Mn-porphyrin derivatives may be a vastly better scavenger of reactive oxygen species in vivo.

  17. Halogenated boron-dipyrromethenes: synthesis, properties and applications.

    PubMed

    Lakshmi, Vellanki; Rao, Malakalapalli Rajeswara; Ravikanth, Mangalampalli

    2015-03-07

    Boron-dipyrromethene dyes (BODIPYs) containing halogens at pyrrole carbons are very useful synthons for the synthesis of a variety of BOIDPYs for a wide range of applications. Among the functional groups, halogens are the functional groups which can be regiospecifically introduced at any desired pyrrole carbon of the BODIPY framework by adopting appropriate synthetic strategies. The halogenated BODIPYs can undergo facile nucleophilic substitution reactions to prepare several interesting BODIPY based compounds. This review describes the synthesis, properties and potential applications of halogenated BODIPYs containing one to six halogens at the pyrrole carbons of the BODIPY core as well as properties and applications of some of the substituted BODIPYs derived from halogenated BODIPYs.

  18. Aerosol-halogen interaction: Change of physico-chemical properties of SOA by naturally released halogen species

    NASA Astrophysics Data System (ADS)

    Ofner, J.; Balzer, N.; Buxmann, J.; Grothe, H.; Krüger, H.; Platt, U.; Schmitt-Kopplin, P.; Zetzsch, C.

    2011-12-01

    Reactive halogen species are released by various sources like photo-activated sea-salt aerosol or salt pans and salt lakes. These heterogeneous release mechanisms have been overlooked so far, although their potential of interaction with organic aerosols like Secondary Organic Aerosol (SOA), Biomass Burning Organic Aerosol (BBOA) or Atmospheric Humic LIke Substances (HULIS) is completely unknown. Such reactions can constitute sources of gaseous organo-halogen compounds or halogenated organic particles in the atmospheric boundary layer. To study the interaction of organic aerosols with reactive halogen species (RHS), SOA was produced from α-pinene, catechol and guaiacol using an aerosol smog-chamber. The model SOAs were characterized in detail using a variety of physico-chemical methods (Ofner et al., 2011). Those aerosols were exposed to molecular halogens in the presence of UV/VIS irradiation and to halogens, released from simulated natural halogen sources like salt pans, in order to study the complex aerosol-halogen interaction. The heterogeneous reaction of RHS with those model aerosols leads to different gaseous species like CO2, CO and small reactive/toxic molecules like phosgene (COCl2). Hydrogen containing groups on the aerosol particles are destroyed to form HCl or HBr, and a significant formation of C-Br bonds could be verified in the particle phase. Carbonyl containing functional groups of the aerosol are strongly affected by the halogenation process. While changes of functional groups and gaseous species were visible using FTIR spectroscopy, optical properties were studied using Diffuse Reflectance UV/VIS spectroscopy. Overall, the optical properties of the processed organic aerosols are significantly changed. While chlorine causes a "bleaching" of the aerosol particles, bromine shifts the maximum of UV/VIS absorption to the red end of the UV/VIS spectrum. Further physico-chemical changes were recognized according to the aerosol size-distributions or the

  19. Halogen bond: a long overlooked interaction.

    PubMed

    Cavallo, Gabriella; Metrangolo, Pierangelo; Pilati, Tullio; Resnati, Giuseppe; Terraneo, Giancarlo

    2015-01-01

    Because of their high electronegativity, halogen atoms are typically considered, in most of their derivatives, as sites of high electron density and it is commonly accepted that they can form attractive interactions by functioning as the electron donor site (nucleophilic site). This is the case when they work as hydrogen bond acceptor sites. However, the electron density in covalently bound halogens is anisotropically distributed. There is a region of higher electron density, accounting for the ability of halogens to function as electron donor sites in attractive interactions, and a region of lower electron density where the electrostatic potential is frequently positive (mainly in the heavier halogens). This latter region is responsible for the ability of halogen atoms to function as the electron-acceptor site (electrophilic site) in attractive interactions formed with a variety of lone pair-possessing atoms, anions, and π-systems. This ability is quite general and is shown by a wide diversity of halogenated compounds (e.g., organohalogen derivatives and dihalogens). According to the definition proposed by the International Union of Pure and Applied Chemistry, any attractive interactions wherein the halogen atom is the electrophile is named halogen bond (XB). In this chapter, it is discussed how the practice and the concept of XB developed and a brief history of the interaction is presented. Papers (either from the primary or secondary literature) which have reported major experimental findings in the field or which have given important theoretical contributions for the development of the concept are recollected in order to trace how a unifying and comprehensive categorization emerged encompassing all interactions wherein halogen atoms function as the electrophilic site.

  20. Halogen bonding in solution: thermodynamics and applications.

    PubMed

    Beale, Thomas M; Chudzinski, Michael G; Sarwar, Mohammed G; Taylor, Mark S

    2013-02-21

    Halogen bonds are noncovalent interactions in which covalently bound halogens act as electrophilic species. The utility of halogen bonding for controlling self-assembly in the solid state is evident from a broad spectrum of applications in crystal engineering and materials science. Until recently, it has been less clear whether, and to what extent, halogen bonding could be employed to influence conformation, binding or reactivity in the solution phase. This tutorial review summarizes and interprets solution-phase thermodynamic data for halogen bonding interactions obtained over the past six decades and highlights emerging applications in molecular recognition, medicinal chemistry and catalysis.

  1. Cobalt-cadmium bimetallic porphyrin coordination polymers for electrochemistry application

    NASA Astrophysics Data System (ADS)

    Wang, C. Y.; Cui, G. Y.; Ding, D.; Zhou, B.

    2018-01-01

    In this paper, we used tetra (4-carboxyphenyl) porphyrin (H2TCPP) and metal cadmium, cobalt as reactants to synthesize metal porphyrin coordination polymers that they had different metal ratio. They were expressed as Co1Cd3TCPP, Co1Cd1TCPP, Co3Cd1TCPP, respectively. The results were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and inductively coupled plasma atomic emission spectrometer (ICP). Herein, a series of metal porphyrin coordination polymers has multiple metal active centers and constructs electrochemistry sensors. In order to increase the conductivity, multi-walled carbon nanotubes (MWCNTs) can be used to modify the electrodes. The polymer/MWCNTs/GCE electrode was studied by cyclic voltammetry and chronoamperometry as sensor for sodium nitrite. The performance of Co1Cd1TCPP/MWCNTs/GCE electrode is best, the sensitivity for sodium nitrite is 350.95 mA M-1 cm-2 and the. The results indicate that metal porphyrin coordination polymers have excellent performance. It also enriches the application of metal porphyrin coordination polymer in electrochemistry sensor.

  2. Induction of endogenic porphyrin production in bacteria and subsequent photoinactivation by various light sources

    NASA Astrophysics Data System (ADS)

    Nitzan, Yeshayahu; Malik, Zvi; Kauffman, Merav; Ehrenberg, Benjamin

    1997-12-01

    (delta) -aminolevulinic acid (ALA) induces the production of very high amounts of porphyrins in Gram-positive and Gram- negative bacteria. Accumulation of the porphyrins in the bacterial cell is a consequence of the high porphyrin production but most of the porphyrins are excreted from the cells into the medium. By fluorescence, measurements of the endogenic and of the exogenic content of the produced porphyrins can be determined. Bacteria loaded by their own accumulated porphyrins can undergo photoinactivation by various light sources. Killing of S. aureus cells by its endogenic porphyrins can be achieved by illumination with intense blue lights or by HeNe laser. E. coli cells loaded with endogenic porphyrins can be photoinactivated by intense blue and red light.

  3. Adsorption of halogens on metal surfaces

    NASA Astrophysics Data System (ADS)

    Andryushechkin, B. V.; Pavlova, T. V.; Eltsov, K. N.

    2018-06-01

    This paper presents a review of the experimental and theoretical investigations of halogen interaction with metal surfaces. The emphasis was placed on the recent measurements performed with a scanning tunneling microscope in combination with density functional theory calculations. The surface structures formed on metal surface after halogen interaction are classified into three groups: chemisorbed monolayer, surface halide, bulk-like halide. Formation of monolayer structures is described in terms of surface phase transitions. Surface halide phases are considered to be intermediates between chemisorbed halogen and bulk halide. The modern theoretical approaches in studying the dynamics of metal halogenation reactions are also presented.

  4. Efficient sensitization of dye-sensitized solar cells by novel triazine-bridged porphyrin-porphyrin dyads.

    PubMed

    Zervaki, Galateia E; Roy, Mahesh S; Panda, Manas K; Angaridis, Panagiotis A; Chrissos, Emmanouel; Sharma, Ganesh D; Coutsolelos, Athanassios G

    2013-09-03

    Two novel porphyrin-porphyrin dyads, the symmetrical Zn[Porph]-Zn[Porph] (2) and unsymmetrical Zn[Porph]-H2[Porph] (4), where Zn[Porph] and H2[Porph] are the metalated and free-base forms of 5-(4-aminophenyl)-10,15,20-triphenylporphyrin, respectively, in which two porphyrin units are covalently bridged by 1,3,5-triazine, have been synthesized via the stepwise amination of cyanuric chloride. The dyads are also functionalized by a terminal carboxylic acid group of a glycine moiety attached to the triazine group. Photophysical measurements of 2 and 4 showed broaden and strengthened absorptions in their visible spectra, while electrochemistry experiments and density functional theory calculations revealed negligible interaction between the two porphyrin units in their ground states but appropriate frontier orbital energy levels for use in dye-sensitized solar cells (DSSCs). The 2- and 4-based solar cells have been fabricated and found to exhibit power conversion efficiencies (PCEs) of 3.61% and 4.46%, respectively (under an illumination intensity of 100 mW/cm(2) with TiO2 films of 10 μm thickness). The higher PCE value of the 4-based DSSC, as revealed by photovoltaic measurements (J-V curves) and incident photon-to-current conversion efficiency (IPCE) spectra of the two cells, is attributed to its enhanced short-circuit current (J(sc)) under illumination, high open-circuit voltage (V(oc)), and fill factor (FF) values. Electrochemical impedance spectra demonstrated shorter electron-transport time (τd), longer electron lifetime (τe), and high charge recombination resistance for the 4-based cell, as well as larger dye loading onto TiO2.

  5. Halogenated solvent remediation

    DOEpatents

    Sorenson, Kent S.

    2004-08-31

    Methods for enhancing bioremediation of ground water contaminated with nonaqueous halogenated solvents are disclosed. A preferred method includes adding a composition to the ground water wherein the composition is an electron donor for microbe-mediated reductive dehalogenation of the halogenated solvents and enhances mass transfer of the halogenated solvents from residual source areas into the aqueous phase of the ground water. Illustrative compositions effective in these methods include surfactants such as C.sub.2 -C.sub.4 carboxylic acids and hydroxy acids, salts thereof, esters of C.sub.2 -C.sub.4 carboxylic acids and hydroxy acids, and mixtures thereof. Especially preferred compositions for use in these methods include lactic acid, salts of lactic acid, such as sodium lactate, lactate esters, and mixtures thereof. The microbes are either indigenous to the ground water, or such microbes can be added to the ground water in addition to the composition.

  6. Fusing porphyrins with polycyclic aromatic hydrocarbons and heterocycles for optoelectronic applications

    DOEpatents

    Thompson, Mark E.; Diev, Viacheslav; Hanson, Kenneth; Forrest, Stephen R.

    2015-08-18

    A compound that can be used as a donor material in organic photovoltaic devices comprising a non-activated porphyrin fused with one or more non-activated polycyclic aromatic rings or one or more non-activated heterocyclic rings can be obtained by a thermal fusion process. The compounds can include structures of Formula I: ##STR00001## By heating the reaction mixture of non-activated porphyrins with non-activated polycyclic aromatic rings or heterocyclic rings to a fusion temperature and holding for a predetermined time, fusion of one or more polycyclic rings or heterocyclic rings to the non-activated porphyrin core in meso,.beta. fashion is achieved resulting in hybrid structures containing a distorted porphyrin ring with annulated aromatic rings. The porphyrin core can be olygoporphyrins.

  7. [Renal excretion of total porphyrins and hippuric acid in rats].

    PubMed

    Gartzke, J; Burck, D

    1986-09-01

    The amounts of total porphyrins, hippuric acid and creatinine, excreted in urine by adult male Wistar rats, exhibited normal distributions for hippuric acid and creatinine, but a bimodal distribution for total porphyrins. This typical distribution of total porphyrins was still observed when creatinine was used as reference parameter. In biochemical and toxicological experiments in rats, the tested parameters should be therefore be investigated for homogeneity.

  8. Effects of Immersion Solvent on Photovoltaic and Photophysical Properties of Porphyrin-Sensitized Solar Cells.

    PubMed

    Hayashi, Hironobu; Higashino, Tomohiro; Kinjo, Yuriko; Fujimori, Yamato; Kurotobi, Kei; Chabera, Pavel; Sundström, Villy; Isoda, Seiji; Imahori, Hiroshi

    2015-08-26

    Memory effects in self-assembled monolayers (SAMs) of zinc porphyrin carboxylic acid on TiO2 electrodes have been demonstrated for the first time by evaluating the photovoltaic and electron transfer properties of porphyrin-sensitized solar cells prepared by using different immersion solvents sequentially. The structure of the SAM of the porphyrin on the TiO2 was maintained even after treating the porphyrin monolayer with different neat immersion solvents (memory effect), whereas it was altered by treatment with solutions containing different porphyrins (inverse memory effect). Infrared spectroscopy shows that the porphyrins in the SAM on the TiO2 could be exchanged with the same or analogous porphyrin, leading to a change in the structure of the porphyrin SAM. The memory and inverse memory effects are well correlated with a change in porphyrin geometry, mainly the tilt angle of the porphyrin along the long molecular axis from the surface normal on the TiO2, as well as with kinetics of electron transfer between the porphyrin and TiO2. Such a new structure-function relationship for DSSCs will be very useful for the rational design and optimization of photoelectrochemical and photovoltaic properties of molecular assemblies on semiconductor surfaces.

  9. Highly fluorescent peptide nanoribbon impregnated with Sn-porphyrin as a potent DNA sensor.

    PubMed

    Parayil, Sreenivasan Koliyat; Lee, Jooran; Yoon, Minjoong

    2013-05-01

    Highly fluorescent and thermo-stable peptide nanoribbons (PNRs) were fabricated by solvothermal self-assembly of a single peptide (D,D-diphenyl alanine peptides) with Sn-porphyrin (trans-dihydroxo[5,10,15,20-tetrakis(p-tolyl)porphyrinato] Sn(IV) (SnTTP(OH)2)). The structural characterization of the as-prepared nanoribbons was performed by transmitting electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM), FT-IR and Raman spectroscopy, indicating that the lipophilic Sn-porphyrins are impregnated into the porous surface formed in the process of nanoribbon formation through intermolecular hydrogen bonding of the peptide main chains. Consequently the Sn-porphyrin-impregnated peptide nanoribbons (Sn-porphyrin-PNRs) exhibited typical UV-visible absorption spectrum of the monomer porphyrin with a red shifted Q-band, and their fluorescence quantum yield was observed to be enhanced compared to that of free Sn-porphyrin. Interestingly the fluorescence intensity and lifetimes of Sn-porphyrin-PNRs were selectively affected upon interaction with nucleotide base sequences of DNA while those of free Sn-porphyrins were not affected by binding with any of the DNA studied, indicating that DNA-induced changes in the fluorescence properties of Sn-porphyrin-PNRs are due to interaction between DNA and the PNR scaffold. These results imply that Sn-porphyrin-PNR will be useful as a potent fluorescent protein analogue and as a biocompatible DNA sensor.

  10. What’s New in Enzymatic Halogenations

    PubMed Central

    Fujimori, Danica Galoniæ; Walsh, Christopher T.

    2007-01-01

    Summary The halogenation of thousands of natural products occurs during biosynthesis and often confers important functional properties. While haloperoxidases had been the default paradigm for enzymatic incorporation of halogens, via X+ equivalents into organic scaffolds, a combination of microbial genome sequencing, enzymatic studies and structural biology have provided deep new insights into enzymatic transfer of halide equivalents in three oxidation states. These are: (1) the halide ions (X−) abundant in nature, (2) halogen atoms (X•), and (3) the X+ equivalents. The mechanism of halogen incorporation is tailored to the electronic demands of specific substrates and involves enzymes with distinct redox coenzyme requirements. PMID:17881282

  11. Halogenated arsenenes as Dirac materials

    NASA Astrophysics Data System (ADS)

    Tang, Wencheng; Sun, Minglei; Ren, Qingqiang; Wang, Sake; Yu, Jin

    2016-07-01

    Arsenene is the graphene-like arsenic nanosheet, which has been predicted very recently [S. Zhang, Z. Yan, Y. Li, Z. Chen, and H. Zeng, Angewandte Chemie, 127 (2015) 3155-3158]. Using first-principles calculations, we systematically investigate the structures and electronic properties of fully-halogenated arsenenes. Formation energy analysis reveals that all the fully-halogenated arsenenes except iodinated arsenene are energetically favorable and could be synthesized. We have revealed the presence of Dirac cone in fully-halogenated arsenene compounds. They may have great potential applications in next generation of high-performance devices.

  12. Photochemistry of porphyrins: a model for the origin of photosynthesis

    NASA Technical Reports Server (NTRS)

    Mercer-Smith, J. A.; Mauzerall, D. C.

    1984-01-01

    A series of porphyrins and catalysts has been prepared as a model for the origin of photosynthesis on the primordial earth. These compounds have been used to test the hypotheses that (1) the biosynthetic pathway to chlorophyll recapitulates the evolutionary history of photosynthesis, and (2) the proto-photosythetic function of biogenetic porphyrins (biosynthetic chlorophyll precursors) was the oxidation of organic molecules by photoexcited porphyrins with the attendant emission of molecular hydrogen. This paper describes experiments in which photoexcited biogenetic porphyrins oxidize ethylenediamine tetraacetic acid (EDTA). The concomitant reduction of protons to hydrogen gas occurs in the presence of a colloidal platinum catalyst. The addition of methyl viologen, a one-electron shuttle, increases the amount of molecular hydrogen generated during long irradiations and the quantum yield of hydrogen production. When the porphyrin and catalyst are held in association by molecular complexes, the increased efficiency of electron transfer produces higher yields of hydrogen gas.

  13. Evaluation of porphyrin C analogues for photodynamic therapy of cerebral glioma.

    PubMed

    Karagianis, G; Hill, J S; Stylli, S S; Kaye, A H; Varadaxis, N J; Reiss, J A; Phillips, D R

    1996-02-01

    A series of monomeric porphyrins (2-8) based on porphyrin C (1) have been tested as sensitisers for photodynamic therapy (PDT) of cerebral glioma using the in vitro/in vivo C6 intracerebral animal tumour model. The in vivo screening, consisting of cytotoxicity, phototoxicity (red light) and subcellular localisation studies, revealed two sensitisers (porphyrin 7, molecular weight 863 Da and porphyrin 8, molecular weight 889 Da), which had greater photoactivity than porphyrin C and similar photoactivity to haematoporphyrin derivative (HpD) although at a 5-fold higher dose than HpD. Both sensitisers showed intracellular localisation to discrete organelle sites and exhibited considerably less 'dark' cytotoxicity than HpD. The kinetics of uptake of porphyrins 7 and 8 was studied in the mouse C6 glioma model as well as in biopsy samples from normal brain, liver, spleen and blood. Maximal drug uptake levels in tumour occurred 9 and 6 h after intraperitoneal injection for 7 and 8 respectively, at which time the tumour to normal brain ratios were 15:1 and 13:1 respectively. The effect of PDT using porphyrin 7 activated by the gold metal vapour laser tuned to 627.8 nm was studied in Wistar rats bearing intracerebral C6 glioma. At a drug dose of 10 mg porphyrin 7 kg-1 body weight and laser doses of up to 400 J cm-2 light, selective tumour kill with sparing of normal brain was achieved, with a maximal depth of tumour kill of 1.77+/-0.40. mm. Irradiation following a higher drug dose of 75 mg porphyrin 7 kg-1 body weight resulted in a greater depth of tumour kill, but also significantly increased the likelihood and extent of necrosis in normal brain.

  14. Metal halogen battery construction with improved technique for producing halogen hydrate

    DOEpatents

    Fong, Walter L.; Catherino, Henry A.; Kotch, Richard J.

    1983-01-01

    An improved electrical energy storage system comprising, at least one cell having a positive electrode and a negative electrode separated by aqueous electrolyte, a store means wherein halogen hydrate is formed and stored as part of an aqueous material having a liquid level near the upper part of the store, means for circulating electrolyte through the cell, conduit means for transmitting halogen gas formed in the cell to a hydrate forming apparatus associated with the store, said hydrate forming apparatus including, a pump to which there is introduced quantities of the halogen gas and chilled water, said pump being located in the store and an outlet conduit leading from the pump and being substantially straight and generally vertically disposed and having an exit discharge into the gas space above the liquid level in the store, and wherein said hydrate forming apparatus is highly efficient and very resistant to plugging or jamming. The disclosure also relates to an improved method for producing chlorine hydrate in zinc chlorine batteries.

  15. Bioconjugatable Porphyrins Bearing a Compact Swallowtail Motif for Water Solubility

    PubMed Central

    Borbas, K. Eszter; Mroz, Pawel; Hamblin, Michael R.; Lindsey, Jonathan S.

    2011-01-01

    A broad range of applications requires access to water-soluble, bioconjugatable porphyrins. Branched alkyl groups attached at the branching site to the porphyrin meso position are known to impart high organic solubility. Such “swallowtail” motifs bearing a polar group (hydroxy, dihydroxyphosphoryl, dihydroxyphosphoryloxy) at the terminus of each branch have now been incorporated at a meso site in trans-AB-porphyrins. The incorporation of the swallowtail motif relies on rational synthetic methods whereby a 1,9-bis(N-propylimino)dipyrromethane (bearing a bioconjugatable tether at the 5-position) is condensed with a dipyrromethane (bearing a protected 1,5-dihydroxypent-3-yl unit at the 5-position). The two hydroxy groups in the swallowtail motif of each of the resulting zinc porphyrins can be transformed to the corresponding diphosphate or diphosphonate product. A 4-(carboxymethyloxy)phenyl group provides the bioconjugatable tether. The six such porphyrins reported here are highly water-soluble (≥20 mM at room temperature in water at pH 7) as determined by visual inspection, UV–vis absorption spectroscopy, or 1H NMR spectroscopy. Covalent attachment was carried out in aqueous solution with the unprotected porphyrin diphosphonate and a monoclonal antibody against the T-cell receptor CD3ε. The resulting conjugate performed comparably to a commercially available fluorescein isothiocyanate-labeled antibody with Jurkat cells in flow cytometry and fluorescence microscopy assays. Taken together, this work enables preparation of useful quantities of water-soluble, bioconjugatable porphyrins in a compact architecture for applications in the life sciences. PMID:16704201

  16. Peripherally Metalated Porphyrins with Applications in Catalysis, Molecular Electronics and Biomedicine.

    PubMed

    Longevial, Jean-François; Clément, Sébastien; Wytko, Jennifer A; Ruppert, Romain; Weiss, Jean; Richeter, Sébastien

    2018-04-24

    Porphyrins are conjugated, stable chromophores with a central core that binds a variety of metal ions and an easily functionalized peripheral framework. By combining the catalytic, electronic or cytotoxic properties of selected transition metal complexes with the binding and electronic properties of porphyrins, enhanced characteristics of the ensemble are generated. This review article focuses on porphyrins bearing one or more peripheral transition metal complexes and discusses their potential applications in catalysis or biomedicine. Modulation of the electronic properties and intramolecular communication through coordination bond linkages in bis-porphyrin scaffolds is also presented. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Porphyrin as an ideal biomarker in the search for extraterrestrial life.

    PubMed

    Suo, Zhiyong; Avci, Recep; Schweitzer, Mary Higby; Deliorman, Muhammedin

    2007-08-01

    A key issue in astrobiological research is identifying target molecules that are unambiguously biological in origin and can be easily detected and recognized. We suggest porphyrin derivatives as an ideal target, because these chromophores are global in distribution and found in virtually all living organisms on Earth, including microorganisms that may approximate the early evolution of life on Earth. We discuss the inherent qualities that make porphyrin ideally suited for astrobiological research and discuss methods for detecting porphyrin molecules in terrestrial sedimentary environments. We present preliminary data to support the use of ToFSIMS as a powerful technique in the identification of porphyrins.

  18. Selective Aliphatic Carbon-Carbon Bond Activation by Rhodium Porphyrin Complexes.

    PubMed

    To, Ching Tat; Chan, Kin Shing

    2017-07-18

    The carbon-carbon bond activation of organic molecules with transition metal complexes is an attractive transformation. These reactions form transition metal-carbon bonded intermediates, which contribute to fundamental understanding in organometallic chemistry. Alternatively, the metal-carbon bond in these intermediates can be further functionalized to construct new carbon-(hetero)atom bonds. This methodology promotes the concept that the carbon-carbon bond acts as a functional group, although carbon-carbon bonds are kinetically inert. In the past few decades, numerous efforts have been made to overcome the chemo-, regio- and, more recently, stereoselectivity obstacles. The synthetic usefulness of the selective carbon-carbon bond activation has been significantly expanded and is becoming increasingly practical: this technique covers a wide range of substrate scopes and transition metals. In the past 16 years, our laboratory has shown that rhodium porphyrin complexes effectively mediate the intermolecular stoichiometric and catalytic activation of both strained and nonstrained aliphatic carbon-carbon bonds. Rhodium(II) porphyrin metalloradicals readily activate the aliphatic carbon(sp 3 )-carbon(sp 3 ) bond in TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl) and its derivatives, nitriles, nonenolizable ketones, esters, and amides to produce rhodium(III) porphyrin alkyls. Recently, the cleavage of carbon-carbon σ-bonds in unfunctionalized and noncoordinating hydrocarbons with rhodium(II) porphyrin metalloradicals has been developed. The absence of carbon-hydrogen bond activation in these systems makes the reaction unique. Furthermore, rhodium(III) porphyrin hydroxide complexes can be generated in situ to selectively activate the carbon(α)-carbon(β) bond in ethers and the carbon(CO)-carbon(α) bond in ketones under mild conditions. The addition of PPh 3 promotes the reaction rate and yield of the carbon-carbon bond activation product. Thus, both rhodium

  19. Halogenated compounds from marine algae.

    PubMed

    Cabrita, Maria Teresa; Vale, Carlos; Rauter, Amélia Pilar

    2010-08-09

    Marine algae produce a cocktail of halogenated metabolites with potential commercial value. Structures exhibited by these compounds go from acyclic entities with a linear chain to complex polycyclic molecules. Their medical and pharmaceutical application has been investigated for a few decades, however other properties, such as antifouling, are not to be discarded. Many compounds were discovered in the last years, although the need for new drugs keeps this field open as many algal species are poorly screened. The ecological role of marine algal halogenated metabolites has somehow been overlooked. This new research field will provide valuable and novel insight into the marine ecosystem dynamics as well as a new approach to comprehending biodiversity. Furthermore, understanding interactions between halogenated compound production by algae and the environment, including anthropogenic or global climate changes, is a challenging target for the coming years. Research of halogenated metabolites has been more focused on macroalgae than on phytoplankton. However, phytoplankton could be a very promising material since it is the base of the marine food chain with quick adaptation to environmental changes, which undoubtedly has consequences on secondary metabolism. This paper reviews recent progress on this field and presents trends on the role of marine algae as producers of halogenated compounds.

  20. Halogenated Compounds from Marine Algae

    PubMed Central

    Cabrita, Maria Teresa; Vale, Carlos; Rauter, Amélia Pilar

    2010-01-01

    Marine algae produce a cocktail of halogenated metabolites with potential commercial value. Structures exhibited by these compounds go from acyclic entities with a linear chain to complex polycyclic molecules. Their medical and pharmaceutical application has been investigated for a few decades, however other properties, such as antifouling, are not to be discarded. Many compounds were discovered in the last years, although the need for new drugs keeps this field open as many algal species are poorly screened. The ecological role of marine algal halogenated metabolites has somehow been overlooked. This new research field will provide valuable and novel insight into the marine ecosystem dynamics as well as a new approach to comprehending biodiversity. Furthermore, understanding interactions between halogenated compound production by algae and the environment, including anthropogenic or global climate changes, is a challenging target for the coming years. Research of halogenated metabolites has been more focused on macroalgae than on phytoplankton. However, phytoplankton could be a very promising material since it is the base of the marine food chain with quick adaptation to environmental changes, which undoubtedly has consequences on secondary metabolism. This paper reviews recent progress on this field and presents trends on the role of marine algae as producers of halogenated compounds. PMID:20948909

  1. Porphyrin involvement in redshift fluorescence in dentin decay

    NASA Astrophysics Data System (ADS)

    Slimani, A.; Panayotov, I.; Levallois, B.; Cloitre, T.; Gergely, C.; Bec, N.; Larroque, C.; Tassery, H.; Cuisinier, F.

    2014-05-01

    The aim of this study was to evaluate the porphyrin involvement in the red fluorescence observed in dental caries with Soprolife® light-induced fluorescence camera in treatments mode (SOPRO, ACTEON Group, La Ciotat, France) and Vistacam® camera (DÜRR DENTAL AG, Bietigheim-Bissingen, Germany). The International Caries Detection and Assessment System (ICDAS) was used to rand the samples. Human teeth cross-sections, ranked from ICDAS score 0 to 6, were examined by epi-fluorescence microscopy and Confocal Raman microscopy. Comparable studies were done with Protoporphyrin IX, Porphyrin I and Pentosidine solutions. An RGB analysis of Soprolife® images was performed using ImageJ Software (1.46r, National Institutes of Health, USA). Fluorescence spectroscopy and MicroRaman spectroscopy revealed the presence of Protoporphyrin IX, in carious enamel, dentin and dental plaque. However, the presence of porphyrin I and pentosidine cannot be excluded. The results indicated that not only porphyrin were implicated in the red fluorescence, Advanced Glygation Endproducts (AGEs) of the Maillard reaction also contributed to this phenomenon.

  2. Nitrated metalloporphyrins as catalysts for alkane oxidation

    DOEpatents

    Ellis, Jr., Paul E.; Lyons, James E.

    1992-01-01

    Alkanes are oxidized by contact with oxygen-containing gas in the presence as catalyst of a metalloporphyrin in which hydrogen atoms in the porphyrin ring have been replaced with one or more nitro groups. Hydrogen atoms in the porphyrin ring may also be substituted with halogen atoms.

  3. Cyano- and polycyanometalloporphyrins as catalysts for alkane oxidation

    DOEpatents

    Ellis, Jr., Paul E.; Lyons, James E.

    1992-01-01

    Alkanes are oxidized by contact with oxygen-containing gas in the presence as catalyst of a metalloporphyrin in which hydrogen atoms in the porphyrin ring have been substituted with one or more cyano groups. Hydrogen atoms in the porphyrin ring may also be substituted with halogen atoms.

  4. Reduced graphene oxide and porphyrin. An interactive affair in 2-D.

    PubMed

    Wojcik, Aleksandra; Kamat, Prashant V

    2010-11-23

    Photoexcited cationic 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate) (TMPyP) undergoes charge-transfer interaction with chemically reduced graphene oxide (RGO). Formation of the ground-state TMPyP-RGO complex in solution is marked by the red-shift of the porphyrin absorption band. This complexation was analyzed by Benesi-Hildebrand plot. Porphyrin fluorescence lifetime reduced from 5 to 1 ns upon complexation with RGO, indicating excited-state interaction between singlet excited porphyrin and RGO. Femtosecond transient absorption measurements carried out with TMPyP adsorbed on RGO film revealed fast decay of the singlet excited state, followed by the formation of a longer-living product with an absorption maximum around 515 nm indicating the formation of a porphyrin radical cation. The ability of TMPyP-RGO to undergo photoinduced charge separation was further confirmed from the photoelectrochemical measurements. TMPyP-RGO coated conducting glass electrodes are capable of generating photocurrent under visible excitation. These results are indicative of the electron transfer between photoexcited porphyrin and RGO. The role of graphene in accepting and shuttling electrons in light-harvesting assemblies is discussed.

  5. Fluorescence spectroscopy for endogenous porphyrins in human facial skin

    NASA Astrophysics Data System (ADS)

    Seo, I.; Tseng, S. H.; Cula, G. O.; Bargo, P. R.; Kollias, N.

    2009-02-01

    The activity of certain bacteria in skin is known to correlate to the presence of porphyrins. In particular the presence of coproporphyrin produced by P.acnes inside plugged pores has been correlated to acne vulgaris. Another porphyrin encountered in skin is protoporphyrin IX, which is produced by the body in the pathway for production of heme. In the present work, a fluorescence spectroscopy system was developed to measure the characteristic spectrum and quantify the two types of porphyrins commonly present in human facial skin. The system is comprised of a Xe lamp both for fluorescence excitation and broadband light source for diffuse reflectance measurements. A computer-controlled filter wheel enables acquisition of sequential spectra, first excited by blue light at 405 nm then followed by the broadband light source, at the same location. The diffuse reflectance spectrum was used to correct the fluorescence spectrum due to the presence of skin chromophores, such as blood and melanin. The resulting fluorescence spectra were employed for the quantification of porphyrin concentration in a population of healthy subjects. The results show great variability on the concentration of these porphyrins and further studies are being conducted to correlate them with skin conditions such as inflammation and acne vulgaris.

  6. Halogen-bonding-triggered supramolecular gel formation

    NASA Astrophysics Data System (ADS)

    Meazza, Lorenzo; Foster, Jonathan A.; Fucke, Katharina; Metrangolo, Pierangelo; Resnati, Giuseppe; Steed, Jonathan W.

    2013-01-01

    Supramolecular gels are topical soft materials involving the reversible formation of fibrous aggregates using non-covalent interactions. There is significant interest in controlling the properties of such materials by the formation of multicomponent systems, which exhibit non-additive properties emerging from interaction of the components. The use of hydrogen bonding to assemble supramolecular gels in organic solvents is well established. In contrast, the use of halogen bonding to trigger supramolecular gel formation in a two-component gel (‘co-gel’) is essentially unexplored, and forms the basis for this study. Here, we show that halogen bonding between a pyridyl substituent in a bis(pyridyl urea) and 1,4-diiodotetrafluorobenzene brings about gelation, even in polar media such as aqueous methanol and aqueous dimethylsulfoxide. This demonstrates that halogen bonding is sufficiently strong to interfere with competing gel-inhibitory interactions and create a ‘tipping point’ in gel assembly. Using this concept, we have prepared a halogen bond donor bis(urea) gelator that forms co-gels with halogen bond acceptors.

  7. Iron-catalysed fluoroaromatic coupling reactions under catalytic modulation with 1,2-bis(diphenylphosphino)benzene.

    PubMed

    Hatakeyama, Takuji; Kondo, Yoshiyuki; Fujiwara, Yu-Ichi; Takaya, Hikaru; Ito, Shingo; Nakamura, Eiichi; Nakamura, Masaharu

    2009-03-14

    A catalytic amount of 1,2-bis(diphenylphosphino)benzene (DPPBz) achieves selective cleavage of sp(3)-carbon-halogen bond in the iron-catalysed cross-coupling between polyfluorinated arylzinc reagents and alkyl halides, which was unachievable with a stoichiometric modifier such as TMEDA; the selective iron-catalysed fluoroaromatic coupling provides easy and practical access to polyfluorinated aromatic compounds.

  8. Conductive Photo-Activated Porphyrin-ZnO Nanostructured Gas Sensor Array.

    PubMed

    Magna, Gabriele; Catini, Alexandro; Kumar, Raj; Palmacci, Massimo; Martinelli, Eugenio; Paolesse, Roberto; di Natale, Corrado

    2017-04-01

    Chemoresistors working at room temperature are attractive for low-consumption integrated sensors. Previous studies show that this feature can be obtained with photoconductive porphyrins-coated ZnO nanostructures. Furthermore, variations of the porphyrin molecular structure alter both the chemical sensitivity and the photoconductivity, and can be used to define the sensor characteristics. Based on these assumptions, we investigated the properties of an array of four sensors made of a layer of ZnO nanoparticles coated with porphyrins with the same molecular framework but different metal atoms. The array was tested with five volatile organic compounds (VOCs), each measured at different concentrations. Results confirm that the features of individual porphyrins influence the sensor behavior, and the differences among sensors are enough to enable the discrimination of volatile compounds disregarding their concentration.

  9. Investigation of Porphyrin and Lipid Supramolecular Assemblies for Cancer Imaging and Therapy

    NASA Astrophysics Data System (ADS)

    Ng, Kenneth Ka-Seng

    Aerobic life on earth is made possible through the functions of the porphyrin. These colorful and ubiquitous chromophores are efficient at concentrating and converting sunlight into chemical energetic potential which sustain biological life. Humans have had a longstanding fascination with these molecules, especially for their applications in photodynamic therapy. The photophysical properties of porphyrins are highly influenced by their surrounding environment. Intermolecular interactions between these pigments can lead to excited state quenching, energy transfer and large changes to their absorption and fluorescence spectra. This thesis is focused on utilizing molecular self-assembly strategies to develop nanoscale porphyrin and phospholipid structures. The rationale being that intermolecular interactions between porphyrins in these nanostructures can induce changes which can be exploited in novel biomedical imaging and therapeutic applications. Four lipid-based structural platforms are studied including: nanoemulsions, bilayer discs and nanovesicles. In Chapter 1, I provide a background on the photophysics of porphyrins and the effect of intermolecular porphyrin interactions on photophysical properties. I also discuss phospholipids and their self-assembly process. Lastly I review current biomedical photonics techniques and discuss how these strategies can be used in conjugation with porphyrin and lipid supramolecular assemblies. In Chapter 2, I investigate the influence that loading a novel bacteriochlorin photosensitizer into a protein-stabilized lipid emulsion has on its spectral properties. I discovered that while the dye can be incorporated into the lipid emulsion, no changes were observed in its spectral properties. In Chapter 3, an amphipathic alpha-helical protein is used to stabilize and organize porphyrin-lipid molecules into bilayer discs. Close packing between porphyrin molecules causes quenching, which can be reversed by structural degradation of the

  10. Challenging Density Functional Theory Calculations with Hemes and Porphyrins.

    PubMed

    de Visser, Sam P; Stillman, Martin J

    2016-04-07

    In this paper we review recent advances in computational chemistry and specifically focus on the chemical description of heme proteins and synthetic porphyrins that act as both mimics of natural processes and technological uses. These are challenging biochemical systems involved in electron transfer as well as biocatalysis processes. In recent years computational tools have improved considerably and now can reproduce experimental spectroscopic and reactivity studies within a reasonable error margin (several kcal·mol(-1)). This paper gives recent examples from our groups, where we investigated heme and synthetic metal-porphyrin systems. The four case studies highlight how computational modelling can correctly reproduce experimental product distributions, predicted reactivity trends and guide interpretation of electronic structures of complex systems. The case studies focus on the calculations of a variety of spectroscopic features of porphyrins and show how computational modelling gives important insight that explains the experimental spectra and can lead to the design of porphyrins with tuned properties.

  11. Challenging Density Functional Theory Calculations with Hemes and Porphyrins

    PubMed Central

    de Visser, Sam P.; Stillman, Martin J.

    2016-01-01

    In this paper we review recent advances in computational chemistry and specifically focus on the chemical description of heme proteins and synthetic porphyrins that act as both mimics of natural processes and technological uses. These are challenging biochemical systems involved in electron transfer as well as biocatalysis processes. In recent years computational tools have improved considerably and now can reproduce experimental spectroscopic and reactivity studies within a reasonable error margin (several kcal·mol−1). This paper gives recent examples from our groups, where we investigated heme and synthetic metal-porphyrin systems. The four case studies highlight how computational modelling can correctly reproduce experimental product distributions, predicted reactivity trends and guide interpretation of electronic structures of complex systems. The case studies focus on the calculations of a variety of spectroscopic features of porphyrins and show how computational modelling gives important insight that explains the experimental spectra and can lead to the design of porphyrins with tuned properties. PMID:27070578

  12. Treatment System for Removing Halogenated Compounds from Contaminated Sources

    NASA Technical Reports Server (NTRS)

    Clausen, Christian A. (Inventor); Yestrebsky, Cherie L. (Inventor); Quinn, Jacqueline W. (Inventor)

    2015-01-01

    A treatment system and a method for removal of at least one halogenated compound, such as PCBs, found in contaminated systems are provided. The treatment system includes a polymer blanket for receiving at least one non-polar solvent. The halogenated compound permeates into or through a wall of the polymer blanket where it is solubilized with at least one non-polar solvent received by said polymer blanket forming a halogenated solvent mixture. This treatment system and method provides for the in situ removal of halogenated compounds from the contaminated system. In one embodiment, the halogenated solvent mixture is subjected to subsequent processes which destroy and/or degrade the halogenated compound.

  13. Passivation of quartz for halogen-containing light sources

    DOEpatents

    Falkenstein, Zoran

    1999-01-01

    Lifetime of halogen containing VUV, UV, visible or IR light sources can be extended by passivating the quartz or glass gas containers with halogens prior to filling the quartz with the halogen and rare gas mixtures used to produce the light.

  14. Local Electric Field Effects on Rhodium-Porphyrin and NHC-Gold Catalysts

    DTIC Science & Technology

    2015-01-05

    AFRL-OSR-VA-TR-2015-0023 (NII) - Local Electric Field Effects on Rhodium -Porphyrin and NHC-Gold Catalysts MATTHEW KANAN LELAND STANFORD JUNIOR UNIV...Effects on Rhodium -Porphyrin and NHC-Gold Catalysts Principal Investigator: Matthew W. Kanan Project Publications: 1. “An Electric Field–Induced Change...Stanford University Grant/Contract Title The full title of the funded effort. (NII)-Local Electric Field Effects on Rhodium -Porphyrin and NHC-Gold

  15. Interactions of tetracationic porphyrins with DNA and their effects on DNA cleavage

    NASA Astrophysics Data System (ADS)

    Lebedeva, Natalya Sh.; Yurina, Elena S.; Gubarev, Yury A.; Syrbu, Sergey A.

    2018-06-01

    The interaction of tetracationic porphyrins with DNA was studied using UV-Vis absorption, fluorescence spectroscopy and viscometry, and the particle sizes were determined. Аs cationic porphyrins, two isomer porphyrins, 3,3‧,3″,3‴-(5,10,15,20-Porphyrintetrayl)tetrakis(1-methylpyridinium) (TMPyP3) and 4,4‧,4″,4‴-(5,10,15,20-Porphyrintetrayl)tetrakis(1-methylpyridinium) (TMPyP4), were studied. They differ in the position of NCH3+ group in phenyl ring of the porphyrins and hence, in degree of freedom of rotation of the phenyl rings about the central macrocycle. It was found that intercalated complexes are formed at DNA/porphyrin molar ratios (R) of 2.2 and 3.9 for TMPyP3 и TMPyP4, respectively. Decreasing R up to 0.4 and 0.8 for TMPyP3 и TMPyP4, respectively, leads mainly to formation of outside complexes due to π-π stacking between the porphyrin chromophores interacting electrostatically with phosphate framework of DNA. Each type of the obtained complexes was characterized using Scatchard approach. It was ascertained that the affinity of TMPyP4 to DNA is stronger than TMPyP3, meanwhile the wedge effect of the latter is higher. The differences between the porphyrin isomers become more evident at irradiation of their complexes with DNA. It was established that irradiation of the intercalated complexes results in DNA fragmentation. In the case of TMPyP4, DNA fragments of different size are formed. The irradiation of the outside DNA/porphyrin complexes leads to cleavage of DNA (TMPyP3 and TMPyP4) and partial destruction of the complex due to photolysis of the porphyrin (TMPyP3).

  16. All substituted nickel porphyrins are highly nonplanar

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shelnutt, J.A.; Song, X.Z.; Jentzen, W.

    1996-12-31

    X-ray crystallographic and resonance Raman studies show that only un-substituted Ni porphine is planar in solution; all substituted Ni porphyrin derivatives either are nonplanar or exist as a mixture of planar and nonplanar conformers in solution. Recent modifications in a molecular mechanics force field improve the ability the MM calculations to predict the X-ray structures of porphyrins and also the planar-nonplanar conformational equilibria in many cases. Calculations using the new force field suggests that all geoporphyrins will be highly nonplanar, especially those having meso substituents. The nonplanarity is expected to influence properties such as solubility and metallation/dematallation reactions. Further, amore » method of quantifying these nonplanar structures has been devised; any porphyrin structure can be decomposed into displacements along the out-of-plane normal coordinates. However, usually distortions along only the lowest-frequency normal modes of each symmetry type are required to adequately describe the structure. The lowest-frequency normal coordinates of b{sub lu}, a{sub 2u}, b{sub 2u}, and e{sub g} symmetries correspond to commonly observed symmetric distortions called ruffling (ruf), doming(dom), saddling (sad), and waving (wav(x), wav(y)). The application of this structural decomposition method to several problems including the influences of steric crowding and protein folding on porphyrin conformation will be described.« less

  17. Synthesis, spectral, and structural studies of porphyrins having sterically hindered [η(5)-CpCo(η(4)-C4Ph4)] cobalt sandwich units at the meso positions.

    PubMed

    Keshav, Karunesh; Kumar, Dheeraj; Elias, Anil J

    2013-11-04

    Synthesis, spectral, and structural studies of the first examples of porphyrins substituted at the meso positions with sterically hindered η(5)-CpCo(η(4)-C4Ph4) cobalt sandwich units are described. The novel dipyrromethane derived cobalt sandwich compound {η(5)-[(C4H4N)2CH]C5H4}Co(η(4)-C4Ph4) 1, as well as its parent aldehyde, η(5)-[C5H4(CHO)]Co(η(4)-C4Ph4), were used in the synthesis of porphyrins having one or two η(5)-CpCo(η(4)-C4Ph4) groups at their meso positions. 1,9-Diformyldipyrromethane derived η(5)-CpCo(η(4)-C4Ph4) 2 was synthesized using dipyrromethane 1 under Vilsmeier conditions. A reaction of 2 with unsubstituted dipyrromethane under basic conditions in the presence of Pd(C6H5CN)2Cl2 yielded an A-type palladium coordinated porphyrin 3 [where A = η(5)-CpCo(η(4)-C4Ph4)]. A similar reaction of 2 with meso aryl and ferrocenyl-substituted dipyrromethanes yielded trans-AB type palladium coordinated porphyrins 4-6 [where A = η(5)-CpCo(η(4)-C4Ph4) and B = 4-tert-butylphenyl 4, ferrocenyl 5, and pentafluorophenyl 6]. Reactions of 2 with 5-ferrocenyl dipyrromethane under the same reaction conditions in the presence of Ni(acac)2 and Zn(OAc)2 gave the trimetallic nickel(II) and zinc(II) complexed trans-AB type porphyrins 7 and 8 having both cobalt and iron sandwich units at the meso positions. Crystal structure of the Pd(II) porphyrin 5 and nickel(II) porphyrin 7 showed nonplanar structures having distinct ruffle type distortion of the porphyrin ring. Demetalation of the zinc(II) trans-AB type porphyrin 8 in the presence of trifluoroacetic acid gave the metal free base porphyrin 9. Reactions of the cobalt sandwich aldehyde [(η(5)-C5H4(CHO)]Co(η(4)-C4Ph4) with sterically hindered dipyrromethane derivatives under acid-catalyzed condensation reactions gave trans-A2B2 type porphyrins [where A = η(5)-CpCo(η(4)-C4Ph4) and B = pentafluorophenyl, 10 mesityl 11]. In contrast, reactions of [η(5)-C5H4(CHO)]Co(η(4)-C4Ph4) with sterically unhindered meso-4

  18. 3D Motions of Iron in Six-Coordinate {FeNO} 7 Hemes by Nuclear Resonance Vibration Spectroscopy [3-D Motions of Iron in Six-coordinate {FeNO} 7 Hemes by NRVS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Peng, Qian; Pavlik, Jeffrey W.; Silvernail, Nathan J.

    The vibrational spectrum of a six-coordinate nitrosyl iron porphyrinate, monoclinic [Fe(T pFPP)(1-MeIm)(NO)] (T pFPP = tetra- para-fluorophenylporphyrin; 1-MeIm=1-methylimidazole), has been studied by oriented single-crystal nuclear resonance vibrational spectroscopy (NRVS). The crystal was oriented to give spectra perpendicular to the porphyrin plane and two in-plane spectra perpendicular or parallel to the projection of the FeNO plane. These enable assignment of the FeNO bending and stretching modes. The measurements reveal that the two in-plane spectra have substantial differences that result from the strongly bonded axial NO ligand. The direction of the in-plane iron motion is found to be largely parallel and perpendicularmore » to the projection of the bent FeNO on the porphyrin plane. The out-of-plane Fe-N-O stretching and bending modes are strongly mixed with each other, as well as with porphyrin ligand modes. The stretch is mixed with v 50 as was also observed for dioxygen complexes. The frequency of the assigned stretching mode of eight Fe-X-O (X= N, C, and O) complexes is correlated with the Fe XO bond lengths. The nature of highest frequency band at ≈560 cm -1 has also been examined in two additional new derivatives. Previously assigned as the Fe NO stretch (by resonance Raman), it is better described as the bend, as the motion of the central nitrogen atom of the FeNO group is very large. There is significant mixing of this mode. In conclusion, the results emphasize the importance of mode mixing; the extent of mixing must be related to the peripheral phenyl substituents.« less

  19. 3D Motions of Iron in Six-Coordinate {FeNO} 7 Hemes by Nuclear Resonance Vibration Spectroscopy [3-D Motions of Iron in Six-coordinate {FeNO} 7 Hemes by NRVS

    DOE PAGES

    Peng, Qian; Pavlik, Jeffrey W.; Silvernail, Nathan J.; ...

    2016-03-21

    The vibrational spectrum of a six-coordinate nitrosyl iron porphyrinate, monoclinic [Fe(T pFPP)(1-MeIm)(NO)] (T pFPP = tetra- para-fluorophenylporphyrin; 1-MeIm=1-methylimidazole), has been studied by oriented single-crystal nuclear resonance vibrational spectroscopy (NRVS). The crystal was oriented to give spectra perpendicular to the porphyrin plane and two in-plane spectra perpendicular or parallel to the projection of the FeNO plane. These enable assignment of the FeNO bending and stretching modes. The measurements reveal that the two in-plane spectra have substantial differences that result from the strongly bonded axial NO ligand. The direction of the in-plane iron motion is found to be largely parallel and perpendicularmore » to the projection of the bent FeNO on the porphyrin plane. The out-of-plane Fe-N-O stretching and bending modes are strongly mixed with each other, as well as with porphyrin ligand modes. The stretch is mixed with v 50 as was also observed for dioxygen complexes. The frequency of the assigned stretching mode of eight Fe-X-O (X= N, C, and O) complexes is correlated with the Fe XO bond lengths. The nature of highest frequency band at ≈560 cm -1 has also been examined in two additional new derivatives. Previously assigned as the Fe NO stretch (by resonance Raman), it is better described as the bend, as the motion of the central nitrogen atom of the FeNO group is very large. There is significant mixing of this mode. In conclusion, the results emphasize the importance of mode mixing; the extent of mixing must be related to the peripheral phenyl substituents.« less

  20. Probing the electronic structure of β,β‧-fused quinoxalino porphyrins and tetraazaanthracene-bridged bis-porphyrins with resonance Raman spectroscopy and density functional theory

    NASA Astrophysics Data System (ADS)

    Elliott, Anastasia B. S.; Gordon, Keith C.; Khoury, Tony; Crossley, Maxwell J.

    2012-12-01

    A number of π-extended porphyrins and bis-porphyrins were characterised by resonance Raman spectroscopy and density functional theory (DFT) calculations, using both B3LYP and CAM-B3LYP functionals. Single porphyrin species, incorporating a β,β'-fused quinoxalino unit, and tetraazaanthracene-bridged bis-porphyrins were investigated. Geometry optimisation predicted all species were planar with respect to the porphyrin core(s). Comparison of experimental with simulated vibrational spectra, obtained via DFT calculations [B3LYP/6-31G(d)], verified the modelling; demonstrated by a mean absolute deviation (MAD) between experimental and calculated band positions of less than 10 cm-1. Simulated electronic transitions obtained via time-dependent DFT [TD-DFT, B3LYP and CAM-B3LYP/6-31G(d)] lay within 0.4 eV of experimental bands and calculations showed perturbation of the frontier molecular orbitals (FMOs) following substitution of the porphyrin core. The nature of transitions that were investigated experimentally via resonance Raman enhancement showed consistency with the character of calculated transitions. A wavepacket analysis of the resonance Raman intensities provided electronic parameters, such as reorganisation energy, as well as normal mode displacements (Δi) that were also consistent with the nature of the specific vibrational modes and probed optical transitions. The largest vibrational reorganisation value obtained was for the Bsh band of compound (1). This result is consistent with the greater electron density shift of the transition found from DFT and resonance Raman and also the less symmetrical nature of (1).

  1. METHOD FOR PRODUCING ISOTOPIC METHANES AND PARTIALLY HALOGENATED DERIVATIVES THEROF

    DOEpatents

    Frazer, J.W.

    1959-08-18

    A method is given for producing isotopic methanes and/ or partially halogenated derivatives. Lithium hydride, deuteride, or tritide is reacted with a halogenated methane or with a halogenated methane in combination with free halogen. The process is conveniently carried out by passing a halogenated methane preferably at low pressures or in an admixture with an inert gas through a fixed bed of finely divided lithium hydride heated initially to temperatures of 100 to 200 deg C depending upon the halogenated methane used.

  2. Synthesis and binding properties of arylethyne-linked porphyrin-zinc complexes for organic electronics applications.

    PubMed

    Reainthippayasakul, W; Paosawatyanyong, B; Bhanthumnavin, W

    2013-05-01

    Conjugated meso-alkynyl 5,15-dimesitylporphyrin metal complexes have been synthesized by Sonogashira coupling reaction in good yields. Alkynyl groups were chosen as a link at the meso positions in order to extend the pi-conjugated length of porphyrin rings. These synthesized porphyrin derivatives were characterized by 1H NMR spectroscopy and MALDI-TOF mass spectrometry. Moreover, UV-visible spectroscopy and fluorescence spectroscopy were also used to investigate their photophysical properties. It has been demonstrated that central metal ions as well as meso substituents on porphyrin rings affected the electronic absorption and emission spectra of the compounds. Spectroscopic results revealed that alkyne-linked porphyrin metal complexes showed higher pi-conjugation compared with porphyrin building blocks resulting in red shifts in both absorption and emission spectra. Coordination properties of synthesized porphyrins were preliminarily investigated by UV-visible absorption and fluorescence emission spectroscopic titration with pyridine as axial ligand. The formation of porphyrin-pyridine complexes resulted in significant red shifts in absorption spectra and decrease of fluorescence intensity in emission spectra. Moreover, the 1H NMR titration experiments suggested that central metal ions play an important role to coordinate with pyridine and the coordination of porphyrin zinc(II) complex with pyridine occur in a 1:1 ratio. From these spectroscopic results, alkyne-linked porphyrin metal complexes offer potential applications as materials for optical organic nanosensors.

  3. Dual fluorescence from two erbium(III) porphyrins

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kaizu, Y.; Asano, M.; Kobayashi, H.

    1986-08-14

    TPPErOH (TPP, 5,10,15,20-tetraphenylporphin) as well as TPPEr(dpm)(dpm, 2,2,6,6-tetramethyl-3,5-heptanedione) fluoresces not only from the lowest excited singlet (S/sub 1/) state but also from the second excited singlet (S/sub 2/) state, while OEPErOH (OEP, 2,3,7,8,12,13,17,18-octaethylporphin) emits only from S/sub 1/ state. TPPEr(dpm) is in two different conformations in methanol/ethanol (7:3 v/v) glass at 77 K; the conformer with the central metal ion displaced out of the porphyrin plane emits no S/sub 2/ fluorescence, while the other conformer with the central metal ion in the porphyrin plane does emit S/sub 2/ fluorescence. Upon irradiation in the ultraviolet band around 300 nm, TPPEr(dpm) emitsmore » form both porphyrin S/sub 2/ and coordinated ..beta..-diketone T/sub 1/ (the lowest excited triplet) states.« less

  4. Investigation of photodynamic activity of water-soluble porphyrins in vitro and in vivo

    NASA Astrophysics Data System (ADS)

    Gyulkhandanyan, Grigor V.; Ghambaryan, Sona S.; Amelyan, Gayane V.; Ghazaryan, Robert K.; Arsenyan, Flora H.; Gyulkhandanyan, Aram G.

    2006-02-01

    Photodynamic therapy (PDT) is the method of photosensitized tumor treatment. It is based on the photosensitizer (PS) selective accumulation in tumors, its subsequent activation under the light influence and oxygen active form formation that results in tumor destruction. Photodynamic action of some new water-soluble porphyrins was investigated in our laboratory. Dose-dependent effect of these porphyrins was shown on PC-12 murine pheochromocytoma cell line. The results revealed that the efficiency of the investigated porphyrins decreased in the following way: TOEPyP (meso-tetra-(4-N-oxyethylpyridyl)porphyrin) > Zn-TOEPyP > Ag-TOEPyP. It was shown that TOEPyP possessed nearly the same photodynamic activity (LD50) as well-known photosensitizer chlorin e6. These porphyrins have also demonstrated quite high photodynamic activity in vivo. The results were obtained in the experiments on white mice with engrafted C-180 (Croker's sarcoma). Antitumor activity of these porphyrins in the dark was 30-40%, whereas photodynamic activity was 45-60%.

  5. Two novel self-assemblies of supramolecular solar cells using N-heterocyclic-anchoring porphyrins.

    PubMed

    Zhang, Qian; Wu, Fang-Yuan; Liu, Jia-Cheng; Li, Ren-Zhi; Jin, Neng-Zhi

    2018-02-15

    Two novel N-substituted anchoring porphyrins (ZnPAtz and ZnPAim) have been devised and synthesized. Moreover, these two anchoring porphyrins were linked to the TiO 2 semiconductor through carboxyl groups and then a zinc porphyrin ZnP was bound to the anchoring porphyrin using a zinc-to-ligand axial coordination approach. The different performances of these assemblies were compared with single anchoring porphyrin devices ZnPAtz and ZnPAim. The photoelectric conversion efficiency of the new supramolecular solar cells sensitized by ZnP-ZnPAx (x=tz, im) has been improved. The ZnP-ZnPAtz-based DSSCs provided the highest photovoltaic efficiency (1.86%). Fundamental studies showed that incorporation of these assemblies promote light-harvesting efficiency. Copyright © 2017. Published by Elsevier B.V.

  6. Experimental and computational evidence of halogen bonds involving astatine

    NASA Astrophysics Data System (ADS)

    Guo, Ning; Maurice, Rémi; Teze, David; Graton, Jérôme; Champion, Julie; Montavon, Gilles; Galland, Nicolas

    2018-03-01

    The importance of halogen bonds—highly directional interactions between an electron-deficient σ-hole moiety in a halogenated compound and an acceptor such as a Lewis base—is being increasingly recognized in a wide variety of fields from biomedicinal chemistry to materials science. The heaviest halogens are known to form stronger halogen bonds, implying that if this trend continues down the periodic table, astatine should exhibit the highest halogen-bond donating ability. This may be mitigated, however, by the relativistic effects undergone by heavy elements, as illustrated by the metallic character of astatine. Here, the occurrence of halogen-bonding interactions involving astatine is experimentally evidenced. The complexation constants of astatine monoiodide with a series of organic ligands in cyclohexane solution were derived from distribution coefficient measurements and supported by relativistic quantum mechanical calculations. Taken together, the results show that astatine indeed behaves as a halogen-bond donor—a stronger one than iodine—owing to its much more electrophilic σ-hole.

  7. Self-assembled nanoscale DNA-porphyrin complex for artificial light harvesting.

    PubMed

    Woller, Jakob G; Hannestad, Jonas K; Albinsson, Bo

    2013-02-20

    Mimicking green plants' and bacteria's extraordinary ability to absorb a vast number of photons and harness their energy is a longstanding goal in artificial photosynthesis. Resonance energy transfer among donor dyes has been shown to play a crucial role on the overall transfer of energy in the natural systems. Here, we present artificial, self-assembled, light-harvesting complexes consisting of DNA scaffolds, intercalated YO-PRO-1 (YO) donor dyes and a porphyrin acceptor anchored to a lipid bilayer, conceptually mimicking the natural light-harvesting systems. A model system consisting of 39-mer duplex DNA in a linear wire configuration with the porphyrin attached in the middle of the wire is primarily investigated. Utilizing intercalated donor fluorophores to sensitize the excitation of the porphyrin acceptor, we obtain an effective absorption coefficient 12 times larger than for direct excitation of the porphyrin. On the basis of steady-state and time-resolved emission measurements and Markov chain simulations, we show that YO-to-YO resonance energy transfer substantially contributes to the overall flow of energy to the porphyrin. This increase is explained through energy migration along the wire allowing the excited state energy to transfer to positions closer to the porphyrin. The versatility of DNA as a structural material is demonstrated through the construction of a more complex, hexagonal, light-harvesting scaffold yielding further increase in the effective absorption coefficient. Our results show that, by using DNA as a scaffold, we are able to arrange chromophores on a nanometer scale and in this way facilitate the assembly of efficient light-harvesting systems.

  8. Transition from metal-ligand bonding to halogen bonding involving a metal as halogen acceptor a study of Cu, Ag, Au, Pt, and Hg complexes

    NASA Astrophysics Data System (ADS)

    Oliveira, Vytor; Cremer, Dieter

    2017-08-01

    Utilizing all-electron Dirac-exact relativistic calculations with the Normalized Elimination of the Small Component (NESC) method and the local vibrational mode approach, the transition from metal-halide to metal halogen bonding is determined for Au-complexes interacting with halogen-donors. The local stretching force constants of the metal-halogen interactions reveal a smooth transition from weak non-covalent halogen bonding to non-classical 3-center-4-electron bonding and finally covalent metal-halide bonding. The strongest halogen bonds are found for dialkylaurates interacting with Cl2 or FCl. Differing trends in the intrinsic halogen-metal bond strength, the binding energy, and the electrostatic potential are explained.

  9. Porphyrin Induced Laser Deactivation of Trypsinogen-Trypsin Conversion

    NASA Astrophysics Data System (ADS)

    Perido, Joanna; Brancaleon, Lorenzo

    2015-03-01

    Pancreatitis is caused by the inflammation of the pancreas, where the digestive enzyme trypsin is activated from the precursor enzyme trypsinogen while still in the pancreas. The presence of trypsin in the pancreas causes auto-activation of trypsinogen, resulting in greater inflammation and auto-digestion of the pancreas. In severe cases, this cascade effect can lead to organ failure, diabetes, and pancreatic cancer. Our hypothesis is that if trypsinogen is prevented from auto-activating into trypsin, then this cascade can be stopped. We propose to do this by inducing conformational changes in trypsinogen when bound to a photoactive porphyrin dye. Porphyrins are comprised of four linked heterocyclic groups forming a flat ring, and bind well with proteins such as trypsinogen. In this study we used spectroscopic techniques to probe the binding of meso-tetrakis (4-sulfonatephenyl) porphyrin (TSPP) to trypsinogen in vitro, as a preliminary step to then prompt and characterize conformational changes of trypsinogen through irradiation. If conformational changes are detected the trypsinogen will be tested for trypsin inactivation. This investigation may provide promising initial results to the possible use of porphyrins as an inhibitor of the self-activation of trypsinogen into trypsin, and a potential inhibitor of pancreatitis. MARC*U-STAR.

  10. Microscale determination of the spectral characteristics and carbon-isotopic compositions of porphyrins

    NASA Technical Reports Server (NTRS)

    Popp, B. N.; Hayes, J. M.; Boreham, C. J.

    1993-01-01

    Molar extinction coefficients for band III of Ni porphyrins are calculated from results of spectrophotometric and manometric analyses of individual etioporphyrins, DPEP, cyclic, and diDPEP porphyrins known to initially be pure from mass spectrometry, 1H NMR, and analytical HPLC studies. A method for determining carbon-isotopic compositions and purity of micromolar quantities of individual porphyrins using combined spectrophotometric and manometric techniques is presented.

  11. Synthetic Porphyrins and Metalloporphyrins

    DTIC Science & Technology

    1976-12-10

    disease syndromes , drug metabolism and cancer. Porphyrins and metalloporphyrins such as tetraphenylporphine sulfonate and hema- toporphyrin have been found...267(1941). 34. A. D. Adler, F. R. Longo, J. D. Finarelli, J. Goldmacher, J. Assour and L. Korsakoff , J. Org. Chem., 32, 476(1967). 35. H. W

  12. Photodynamic inactivation of Candida albicans sensitized by tri- and tetra-cationic porphyrin derivatives.

    PubMed

    Cormick, M Paula; Alvarez, M Gabriela; Rovera, Marisa; Durantini, Edgardo N

    2009-04-01

    The photodynamic action of 5-(4-trifluorophenyl)-10,15,20-tris(4-trimethylammoniumphenyl)porphyrin iodide (TFAP(3+)) and 5,10,15,20-tetra(4-N,N,N-trimethylammonium phenyl)porphyrin p-tosylate (TMAP(4+)) has been studied in vitro on Candida albicans. The results of these cationic porphyrins were compared with those of 5,10,15,20-tetra(4-sulphonatophenyl)porphyrin (TPPS(4-)), which characterizes an anionic sensitizer. In vitro investigations show that these cationic porphyrins are rapidly bound to C. albicans cells, reaching a value of approximately 1.4 nmol/10(6) cells, when the cellular suspensions were incubated with 5 microM sensitizer for 30 min. In contrast, TPPS(4-) is poorly uptaken by yeast cells. The fluorescence spectra of these sensitizers into the cells confirm this behaviour. The amount of porphyrin binds to cells is dependent on both sensitizer concentrations (1-5 microM) and cells densities (10(6)-10(8) cells/mL). Photosensitized inactivation of C. albicans cellular suspensions increases with sensitizer concentration, causing a approximately 5 log decrease of cell survival, when the cultures are treated with 5 microM of cationic porphyrin and irradiated for 30 min. However, the photocytotoxicity decreases with an increase in the cell density, according to its low binding to cells. Under these conditions, the photodynamic activity of TFAP(3+) is quite similar to that produced by TMAP(4+), whereas no important inactivation effect was found for TPPS(4)(-). The high photodynamic activity of cationic porphyrins was confirmed by growth delay experiments. Thus, C. albicans cell growth was not detected in the presence of 5 microM TFAP(3+). Photodynamic inactivation capacities of these sensitizers were also evaluated on C. albicans cells growing in colonies on agar surfaces. Cationic porphyrins produce a growth delay of C. albicans colonies and viability of cells was not observed after 3 h irradiation, indicating a complete inactivation of yeast cells

  13. Removal of Intermediate Aromatic Halogenated DBPs by Activated Carbon Adsorption: A New Approach to Controlling Halogenated DBPs in Chlorinated Drinking Water.

    PubMed

    Jiang, Jingyi; Zhang, Xiangru; Zhu, Xiaohu; Li, Yu

    2017-03-21

    During chlorine disinfection of drinking water, chlorine may react with natural organic matter (NOM) and bromide ion in raw water to generate halogenated disinfection byproducts (DBPs). To mitigate adverse effects from DBP exposure, granular activated carbon (GAC) adsorption has been considered as one of the best available technologies for removing NOM (DBP precursor) in drinking water treatment. Recently, we have found that many aromatic halogenated DBPs form in chlorination, and they act as intermediate DBPs to decompose and form commonly known DBPs including trihalomethanes and haloacetic acids. In this work, we proposed a new approach to controlling drinking water halogenated DBPs by GAC adsorption of intermediate aromatic halogenated DBPs during chlorination, rather than by GAC adsorption of NOM prior to chlorination (i.e., traditional approach). Rapid small-scale column tests were used to simulate GAC adsorption in the new and traditional approaches. Significant reductions of aromatic halogenated DBPs were observed in the effluents with the new approach; the removals of total organic halogen, trihalomethanes, and haloacetic acids by the new approach always exceeded those by the traditional approach; and the effluents with the new approach were considerably less developmentally toxic than those with the traditional approach. Our findings indicate that the new approach is substantially more effective in controlling halogenated DBPs than the traditional approach.

  14. Cofacial porphyrin-ferrocene dyads and a new class of conjugated porphyrin.

    PubMed

    Cammidge, Andrew N; Scaife, Peter J; Berber, Gûlen; Hughes, David L

    2005-08-04

    A porphyrin-ferrocene dyad has been synthesized in which there is close face-to-face contact between the two aromatic systems, providing a model for heterobimetallic polymers based on the same repeating unit. Attempts to synthesize the 2:1 adduct instead led to a remarkable intramolecular Heck-type cyclization which planarizes the system and extends the conjugation. [structure: see text

  15. The halogen bond: Nature and applications

    NASA Astrophysics Data System (ADS)

    Costa, Paulo J.

    2017-10-01

    The halogen bond, corresponding to an attractive interaction between an electrophilic region in a halogen (X) and a nucleophile (B) yielding a R-X⋯B contact, found applications in many fields such as supramolecular chemistry, crystal engineering, medicinal chemistry, and chemical biology. Their large range of applications also led to an increased interest in their study using computational methods aiming not only at understanding the phenomena at a fundamental level, but also to help in the interpretation of results and guide the experimental work. Herein, a succinct overview of the recent theoretical and experimental developments is given starting by discussing the nature of the halogen bond and the latest theoretical insights on this topic. Then, the effects of the surrounding environment on halogen bonds are presented followed by a presentation of the available method benchmarks. Finally, recent experimental applications where the contribution of computational chemistry was fundamental are discussed, thus highlighting the synergy between the lab and modeling techniques.

  16. Magnesium Bisamide-Mediated Halogen Dance of Bromothiophenes.

    PubMed

    Yamane, Yoshiki; Sunahara, Kazuhiro; Okano, Kentaro; Mori, Atsunori

    2018-03-16

    A magnesium bisamide-mediated halogen dance of bromothiophenes is described. The thienylmagnesium species generated in situ is more stable than the corresponding thienyllithium species, which was applied to trap the transient anion species with several electrophiles, such as allyl iodide, phenyl isocyanate, and tributylstannyl chloride. The utility of the magnesium bisamide-mediated halogen dance is useful in the concise synthesis of a medicinally advantageous compound via a one-pot, ester-directed halogen dance/Negishi cross coupling.

  17. Hydrogen bond and halogen bond inside the carbon nanotube

    NASA Astrophysics Data System (ADS)

    Wang, Weizhou; Wang, Donglai; Zhang, Yu; Ji, Baoming; Tian, Anmin

    2011-02-01

    The hydrogen bond and halogen bond inside the open-ended single-walled carbon nanotubes have been investigated theoretically employing the newly developed density functional M06 with the suitable basis set and the natural bond orbital analysis. Comparing with the hydrogen or halogen bond in the gas phase, we find that the strength of the hydrogen or halogen bond inside the carbon nanotube will become weaker if there is a larger intramolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom donor to the antibonding orbital of the X-H or X-Hal bond involved in the formation of the hydrogen or halogen bond and will become stronger if there is a larger intermolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom acceptor to the antibonding orbital of the X-H or X-Hal bond. According to the analysis of the molecular electrostatic potential of the carbon nanotube, the driving force for the electron-density transfer is found to be the negative electric field formed in the carbon nanotube inner phase. Our results also show that the X-H bond involved in the formation of the hydrogen bond and the X-Hal bond involved in the formation of the halogen bond are all elongated when encapsulating the hydrogen bond and halogen bond within the carbon nanotube, so the carbon nanotube confinement may change the blue-shifting hydrogen bond and the blue-shifting halogen bond into the red-shifting hydrogen bond and the red-shifting halogen bond. The possibility to replace the all electron nanotube-confined calculation by the simple polarizable continuum model is also evaluated.

  18. Enzymatic Halogenation and Dehalogenation Reactions: Pervasive and Mechanistically Diverse.

    PubMed

    Agarwal, Vinayak; Miles, Zachary D; Winter, Jaclyn M; Eustáquio, Alessandra S; El Gamal, Abrahim A; Moore, Bradley S

    2017-04-26

    Naturally produced halogenated compounds are ubiquitous across all domains of life where they perform a multitude of biological functions and adopt a diversity of chemical structures. Accordingly, a diverse collection of enzyme catalysts to install and remove halogens from organic scaffolds has evolved in nature. Accounting for the different chemical properties of the four halogen atoms (fluorine, chlorine, bromine, and iodine) and the diversity and chemical reactivity of their organic substrates, enzymes performing biosynthetic and degradative halogenation chemistry utilize numerous mechanistic strategies involving oxidation, reduction, and substitution. Biosynthetic halogenation reactions range from simple aromatic substitutions to stereoselective C-H functionalizations on remote carbon centers and can initiate the formation of simple to complex ring structures. Dehalogenating enzymes, on the other hand, are best known for removing halogen atoms from man-made organohalogens, yet also function naturally, albeit rarely, in metabolic pathways. This review details the scope and mechanism of nature's halogenation and dehalogenation enzymatic strategies, highlights gaps in our understanding, and posits where new advances in the field might arise in the near future.

  19. Dehalogenation of chloroalkanes by nickel(i) porphyrin derivatives, a computational study.

    PubMed

    Szatkowski, L; Hall, M B

    2016-11-14

    The nickel(i) octaethylisobacteriochlorin anion ([OEiBCh-Ni (I) ] - ) is commonly used as a synthetic model of cofactor F 430 from Methyl-Coenzyme M Reductase. In this regard, experimental studies show that [OEiBCh-Ni (I) ] - can catalyze dehalogenation of aliphatic halides in DMF solution by a highly efficient S N 2 reaction. To better understand this process, we constructed theoretical models of the dehalogenation of chloromethane by a simple nickel(i) isobacteriochlorin anion and compared its reactivity with that of similar Ni (I) complexes with other porphyrin-derived ligands: porphyrin, chlorin, bactreriochlorin, hexahydroporphyrin and octahydroporphyrin. Our calculations predict that all of the porphyrin derivative's model reactions proceed through low-spin complexes. Relative to the energy of the separate reactants the theoretical activation energies (free-energy barriers with solvation corrections) for the dehalogenation of chloromethane are similar for all of the porphyrin derivatives and range for the different functionals from 10-15 kcal mol -1 for B3LYP to 5-10 kcal mol -1 for M06-L and to 13-18 kcal mol -1 for ωB97X-D. The relative free energies of the products of the dehalogenation step, L-Ni-Me adducts, have a range from -5 to -40 kcal mol -1 for all functionals; generally becoming more negative with increasing saturation of the porphyrin ligand. Moreover, no significant differences in the theoretical chlorine kinetic isotope effect were discernable with change of porphyrin ligand.

  20. Real-time porphyrin detection in plaque and caries: a case study

    NASA Astrophysics Data System (ADS)

    Timoshchuk, Mari-Alina I.; Ridge, Jeremy S.; Rugg, Amanda L.; Nelson, Leonard Y.; Kim, Amy S.; Seibel, Eric J.

    2015-02-01

    An ultrathin scanning fiber endoscope, originally developed for cancer diagnosis, was used in a case study to locate plaque and caries. The imaging system incorporated software mitigation of background auto-fluorescence (AF). In conventional fluorescence imaging, varying AF across a tooth surface can mask low-level porphyrin signals. Laser-induced auto-fluorescence signals of dental tissue excited using a 405-nm laser typically produce fluorescence over a wavelength range extending from 440-nm to 750-nm. Anaerobic bacterial metabolism produces various porphyrin species (eg. protoporphyrin IX) that are located in carious enamel, dentin, gingivitis sites, and plaque. In our case study, these porphyrin deposits remained as long as one day after prophylaxis. Imaging the tooth surface using 405-nm excitation and subtracting the natural AF enhances the image contrast of low-level porphyrin deposits, which would otherwise be masked by the high background AF. In a case study, healthy tissues as well as sites of early and advanced caries formations were scanned for visual and quantitative signs of red fluorescence associated with porphyrin species using a background mitigation algorithm. Initial findings show increasing amplitudes of red fluorescence as caries severity increases from early to late stages. Sites of plaque accumulation also displayed red fluorescence similar to that found in carious dental tissue. The use of real-time background mitigation of natural dental AF can enhance the detection of low porphyrin concentrations that are indicators of early stage caries formation.

  1. Halogens in chondritic meteorites and terrestrial accretion

    NASA Astrophysics Data System (ADS)

    Clay, Patricia L.; Burgess, Ray; Busemann, Henner; Ruzié-Hamilton, Lorraine; Joachim, Bastian; Day, James M. D.; Ballentine, Christopher J.

    2017-11-01

    Volatile element delivery and retention played a fundamental part in Earth’s formation and subsequent chemical differentiation. The heavy halogens—chlorine (Cl), bromine (Br) and iodine (I)—are key tracers of accretionary processes owing to their high volatility and incompatibility, but have low abundances in most geological and planetary materials. However, noble gas proxy isotopes produced during neutron irradiation provide a high-sensitivity tool for the determination of heavy halogen abundances. Using such isotopes, here we show that Cl, Br and I abundances in carbonaceous, enstatite, Rumuruti and primitive ordinary chondrites are about 6 times, 9 times and 15-37 times lower, respectively, than previously reported and usually accepted estimates. This is independent of the oxidation state or petrological type of the chondrites. The ratios Br/Cl and I/Cl in all studied chondrites show a limited range, indistinguishable from bulk silicate Earth estimates. Our results demonstrate that the halogen depletion of bulk silicate Earth relative to primitive meteorites is consistent with the depletion of lithophile elements of similar volatility. These results for carbonaceous chondrites reveal that late accretion, constrained to a maximum of 0.5 ± 0.2 per cent of Earth’s silicate mass, cannot solely account for present-day terrestrial halogen inventories. It is estimated that 80-90 per cent of heavy halogens are concentrated in Earth’s surface reservoirs and have not undergone the extreme early loss observed in atmosphere-forming elements. Therefore, in addition to late-stage terrestrial accretion of halogens and mantle degassing, which has removed less than half of Earth’s dissolved mantle gases, the efficient extraction of halogen-rich fluids from the solid Earth during the earliest stages of terrestrial differentiation is also required to explain the presence of these heavy halogens at the surface. The hydropilic nature of halogens, whereby they track

  2. Development of Ion Chemosensors Based on Porphyrin Analogues.

    PubMed

    Ding, Yubin; Zhu, Wei-Hong; Xie, Yongshu

    2017-02-22

    Sensing of metal ions and anions is of great importance because of their widespread distribution in environmental systems and biological processes. Colorimetric and fluorescent chemosensors based on organic molecular species have been demonstrated to be effective for the detection of various ions and possess the significant advantages of low cost, high sensitivity, and convenient implementation. Of the available classes of organic molecules, porphyrin analogues possess inherently many advantageous features, making them suitable for the design of ion chemosensors, with the targeted sensing behavior achieved and easily modulated based on their following characteristics: (1) NH moieties properly disposed for binding of anions through cooperative hydrogen-bonding interactions; (2) multiple pyrrolic N atoms or other heteroatoms for selectively chelating metal ions; (3) variability of macrocycle size and peripheral substitution for modulation of ion selectivity and sensitivity; and (4) tunable near-infrared emission and good biocompatibility. In this Review, design strategies, sensing mechanisms, and sensing performance of ion chemosensors based on porphyrin analogues are described by use of extensive examples. Ion chemosensors based on normal porphyrins and linear oligopyrroles are also briefly described. This Review provides valuable information for researchers of related areas and thus may inspire the development of more practical and effective approaches for designing high-performance ion chemosensors based on porphyrin analogues and other relevant compounds.

  3. Process for removal of hydrogen halides or halogens from incinerator gas

    DOEpatents

    Huang, Hann S.; Sather, Norman F.

    1988-01-01

    A process for reducing the amount of halogens and halogen acids in high temperature combustion gases and through their removal, the formation of halogenated organics at lower temperatures, with the reduction being carried out electrochemically by contacting the combustion gas with the negative electrode of an electrochemical cell and with the halogen and/or halogen acid being recovered at the positive electrode.

  4. Process for removal of hydrogen halides or halogens from incinerator gas

    DOEpatents

    Huang, H.S.; Sather, N.F.

    1987-08-21

    A process for reducing the amount of halogens and halogen acids in high temperature combustion gas and through their removal, the formation of halogenated organics at lower temperatures, with the reduction being carried out electrochemically by contacting the combustion gas with the negative electrode of an electrochemical cell and with the halogen and/or halogen acid being recovered at the positive electrode.

  5. Fluorinated Dodecaphenylporphyrins: Synthetic and Electrochemical Studies Including the First Evidence of Intramolecular Electron Transfer Between an Fe(II) Porphyrin -Anion Radical and an Fe(I) Porphyrin

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    D'Souza, F.; Forsyth, T.P.; Fukuzumi, S.

    1998-10-19

    Dodecaphenylporphyrins with varying degrees of fluorination of the peripheral phenyl rings (FXDPPS) were synthesized as model compounds for studying electronic effects in nonplan~ porphyrins, and detailed electrochemical studies of the chloroiron(HI) complexes of these compounds were undertaken. The series of porphyrins, represented as FeDPPCl and as FeFXDPPCl where x = 4, 8 (two isomers), 12, 20,28 or 36, could be reversibly oxidized by two electrons in dichloromethane to give n-cation radicals and n-dications. All of the compounds investigated could also be reduced by three electrons in benzonitrile or pyridine. In benzonitrile, three reversible reductions were observed for the unfluorinated compoundmore » FeDPPC1, whereas the FeFXDPPCl complexes generally exhibited irreversible first and second reductions which were coupled to chemical reactions. The chemical reaction associated with the first reduction involved a loss of the chloride ion after generation of Fe FXDPPC1. The second chemical reaction involved a novel intramolecular electron transfer between the initially generated Fe(H) porphyrin n-anion radical and the final Fe(I) porphyrin reduction product. In pyridine, three reversible one electron reductions were observed with the second reduction affording stable Fe(II) porphyrin o - anion radicals for ail of the complexes investigated.« less

  6. Highly Efficient Cooperative Catalysis by Co III (Porphyrin) Pairs in Interpenetrating Metal-Organic Frameworks

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lin, Zekai; Zhang, Zhi-Ming; Chen, Yu-Sheng

    2016-12-02

    A series of porous twofold interpenetrated In-Co III(porphyrin) metal–organic frameworks (MOFs) were constructed by in situ metalation of porphyrin bridging ligands and used as efficient cooperative catalysts for the hydration of terminal alkynes. The twofold interpenetrating structure brings adjacent Co III(porphyrins) in the two networks parallel to each other with a distance of about 8.8 Å, an ideal distance for the simultaneous activation of both substrates in alkyne hydration reactions. As a result, the In-Co III(porphyrin) MOFs exhibit much higher (up to 38 times) catalytic activity than either homogeneous catalysts or MOF controls with isolated Co III(porphyrin) centers, thus highlightingmore » the potential application of MOFs in cooperative catalysis.« less

  7. Bio-inspired cofacial Fe porphyrin dimers for efficient electrocatalytic CO2 to CO conversion: Overpotential tuning by substituents at the porphyrin rings.

    PubMed

    Zahran, Zaki N; Mohamed, Eman A; Naruta, Yoshinori

    2016-04-18

    Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2. The binuclear Ni, Fe-containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO. The location of Ni and Fe at proper positions allows their cooperation for CO2 to CO conversion through a push-pull mechanism. Bio-inspired from CODHs, we used several cofacial porphyrin dimers with different substituents as suitable ligands for holding two Fe ions with suitable Fe-Fe separation distance to efficiently and selectively promote CO2 to CO conversion with high turnover frequencies, TOFs. The substituents on the porphyrin rings greatly affect the catalysis process. By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups. The Fe porphyrin dimers among reported catalysts are the most efficient ones for CO2 to CO conversion. Control experiments indicate that the high performance of the current CO2 to CO conversion catalysts is due to the presence of binuclear Fe centers at suitable Fe-Fe separation distance.

  8. Bio-inspired cofacial Fe porphyrin dimers for efficient electrocatalytic CO2 to CO conversion: Overpotential tuning by substituents at the porphyrin rings

    NASA Astrophysics Data System (ADS)

    Zahran, Zaki N.; Mohamed, Eman A.; Naruta, Yoshinori

    2016-04-01

    Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2. The binuclear Ni, Fe-containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO. The location of Ni and Fe at proper positions allows their cooperation for CO2 to CO conversion through a push-pull mechanism. Bio-inspired from CODHs, we used several cofacial porphyrin dimers with different substituents as suitable ligands for holding two Fe ions with suitable Fe-Fe separation distance to efficiently and selectively promote CO2 to CO conversion with high turnover frequencies, TOFs. The substituents on the porphyrin rings greatly affect the catalysis process. By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups. The Fe porphyrin dimers among reported catalysts are the most efficient ones for CO2 to CO conversion. Control experiments indicate that the high performance of the current CO2 to CO conversion catalysts is due to the presence of binuclear Fe centers at suitable Fe-Fe separation distance.

  9. Theory favors a stepwise mechanism of porphyrin degradation by a ferric hydroperoxide model of the active species of heme oxygenase.

    PubMed

    Kumar, Devesh; de Visser, Samuël P; Shaik, Sason

    2005-06-08

    The report uses density functional theory to address the mechanism of heme degradation by the enzyme heme oxygenase (HO) using a model ferric hydroperoxide complex. HO is known to trap heme molecules and degrade them to maintain iron homeostasis in the biosystem. The degradation is initiated by complexation of the heme, then formation of the iron-hydroperoxo species, which subsequently oxidizes the meso position of the porphyrin by hydroxylation, thereby enabling eventually the cleavage of the porphyrin ring. Kinetic isotope effect studies indicate that the mechanism is assisted by general acid catalysis, via a chain of water molecules, and that all the events occur in concert. However, previous theoretical treatments indicated that the concerted mechanism has a high barrier, much higher than an alternative mechanism that is initiated by O-O bond homolysis of iron-hydroperoxide. The present contribution studies the stepwise and concerted acid-catalyzed mechanisms using H(3)O(+)(H(2)O)(n)(), n = 0-2. The effect of the acid strength is tested using the H(4)N(+)(H(2)O)(2) cluster and a fully protonated ferric hydroperoxide. All the calculations show that a stepwise mechanism that involves proton relay and O-O homolysis, in the rate-determining step, has a much lower barrier (>10 kcal/mol) than the corresponding fully concerted mechanism. The best fit of the calculated solvent kinetic isotope effect, to the experimental data, is obtained for the H(3)O(+)(H(2)O)(2) cluster. The calculated alpha-deuterium secondary kinetic isotope effect is inverse (0.95-0.98), but much less so than the experimental value (0.7). Possible reasons for this quantitative difference are discussed. Some probes are suggested that may enable experiment to distinguish the stepwise from the concerted mechanism.

  10. J-aggregation in porphyrin nanoparticles induced by diphenylalanine

    NASA Astrophysics Data System (ADS)

    Li, Fengqing; Liu, Dongzhi; Wang, Tianyang; Hu, Jianxin; Meng, Fancui; Sun, Haiya; Shang, Zhi; Li, Pingan; Feng, Wenhui; Li, Wei; Zhou, Xueqin

    2017-08-01

    In this report, L-diphenylalanine-decorated tetraphenylporphyrin (TPPtFFC) was synthesized and self-assembled into regular nano-architechtures. The morphology of the assemblies varied with the concentration of TPPtFFC. The absorption spectra of the nanoparticles show the Soret band merges with the Q bands and redistributes with great red-shift, indicative of the formation of J-aggregates of the porphyrin molecules. The fluorescence emission of the nanoparticles is merged and red-shifted to near-infrared region. Studies of absorption and fluorescence spectra reveal an indispensible role of diphenylalanine group in the formation of J-aggregates. The Raman spectra disclose that diprotonation of the porphyrin core contributes to delocalized coherent excited states in the nanoparticles. The positive cotton effect in circular dichroism spectra corresponding to the Soret band of TPPtFFC in solution confirms the formation of J-aggregates with right-handed chirality of the dipole moment. This report will shed light on the rational design of porphyrin-peptide conjugates to mimic naturally light-harvesting complexes.

  11. Effect of hydroxypropyl-beta-cyclodextrin on the degradation of pentachlorophenol by potassium monopersulfate catalyzed with iron(III)-porphyrin complex.

    PubMed

    Fukushima, Masami; Tatsumi, Kenji

    2005-12-01

    A novel biomimetic catalytic system containing a supramolecular complex between iron(III)-tetrakis(p-sulfonatophenyl)porphyrin [Fe(III)-TPPS] and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) was examined for the potassium monopersulfate catalyzed oxidation of pentachlorophenol (PCP). In the absence of HP-beta-CD, the percentage of PCP disappearance and the numbers of chlorine atoms released from PCP increased to 50% and 1.5 for a 1-day reaction period, respectively. However, in the presence of HP-beta-CD, the PCP completely disappeared and the number of chlorine atoms from PCP was increased to 3.1. o-Tetrachloroquinone, 2- and 4-hydroxyl-nonachlorodiphenyl ethers, and octachlorodibenzo-p-dioxin were detected among the oxidation products. In the absence of HP-beta-CD, the percentage of PCP conversion to oxidation products increased and then reached plateau. In the presence of HP-beta-CD, the amount of oxidation products produced initially increased for the first 10 min and thereafter decreased gradually. These results suggest that the addition of HP-beta-CD results in the further degradation of oxidation products. In addition, the mineralization of PCP to CO2 was investigated using 14C6-labeled PCP. After a 1-day reaction period, 24% of the 14C6-labeled PCP was converted to 14CO2 in the presence of HP-beta-CD, although significant 14CO2 generation was not observed in its absence. The effect of HP-beta-CD on the facilitation of PCP degradation can be attributed to the fact that the self-oxidation of Fe(III)-TPPS is prevented by the formation of a stable supramolecular complex between HP-beta-CD and Fe(III)-TPPS.

  12. DNA binding studies of a new dicationic porphyrin. Insights into interligand interactions.

    PubMed

    Shelton, Alexander H; Rodger, Alison; McMillin, David R

    2007-08-07

    Cationic porphyrins have an affinity for DNA and potential for applications in the fields of photodynamic therapy and cellular imaging. This report describes a new dicationic porphyrin, 5,15-dimethyl-10,20-di(N-methylpyridinium-4-yl)porphyrin, abbreviated H2tMe2D4. Although tetrasubstituted, H2tMe2D4 presents modest steric requirements and forms in reasonable yield by a "2+2" synthetic method. Accordingly, studies of the zinc(II)- and copper(II)-containing derivatives, Zn(tMe2D4) and Cu(tMe2D4), have also been possible. Methods used to characterize DNA-binding motifs include absorption, emission, linear, and circular dichroism spectroscopies, as well as viscometry. An unusually detailed picture of porphyrin uptake emerges. As the ratio of DNA to porphyrin increases during a typical titration, H2tMe2D4 or Cu(tMe2D4) initially aggregates on the host and then shifts to intercalative binding at close quarters before finally dispersing into non-interacting intercalation sites of the host. Emission studies of the copper(II) porphyrin have been very valuable. The existence of a measurable signal is diagnostic of intercalative binding, and the saturation behavior establishes that internalization typically monopolizes approximately three base pairs. In the moderate loading regime, emission data are most telling because dipole-dipole interactions between near-neighbor porphyrins tend to confuse other spectroscopic assays. The third ligand, Zn(tMe2D4), behaves differently in that the uptake is a strictly cooperative process. The mode of binding also varies with the base content of the DNA host. When the DNA is rich in A=T base pairs, the porphyrin remains five-coordinate and binds externally; however, Zn(tMe2D4) loses its axial ligand and binds by intercalation if the host contains only G[triple bond]C base pairs.

  13. Comparison of spectrofluorometric and HPLC methods for the characterization of fecal porphyrins in river otters.

    PubMed

    Taylor, C; Duffy, L K; Plumley, F G; Bowyer, R T

    2000-09-01

    A spectrofluorometric method (B. Grandchamp et al., 1980, Biochem. Biophys. Acta 629, 577-586) developed for the determination of amounts of uroporphyrin I (Uro I), coproporphyrin III (Copro III), and protoporphyrin IX (Proto IX) in skin fibroblasts was compared with a high-performance liquid chromatography (HPLC) method for the analysis of porphyrins in fecal samples of river otters (Lutra canadensis). Heptacarboxylate porphyrin I and coproporphyrin I, two porphyrins determined to be critical in defining the porphyrin profile in fecal samples of river otters with the HPLC method, contributed substantially to the calculation of the concentrations of Uro I and Copro III, respectively, in standard solutions of porphyrins with the spectrofluorometric method. Fluorescent components of the fecal matrix complicated the determination of the concentrations of Uro I, Copro III, and Proto IX with the spectrofluorometric method and resulted in erroneous values for the concentrations of these porphyrins compared with values determined with the HPLC method. These results indicate that the complexity of the sample, particularly with regard to the potential presence of interfering fluorescent compounds, as well as porphyrins additional to Uro I, Copro III, and Proto IX, should be considered prior to the application of the spectrofluorometric method. An alternative HPLC method developed for the rapid characterization of porphyrin profiles in fecal samples of river otters is described. Copyright 2000 Academic Press.

  14. Porphyrin-based Nanostructure-Dependent Photodynamic and Photothermal Therapies

    NASA Astrophysics Data System (ADS)

    Jin, Cheng S.

    This thesis presents the investigation of nanostructure-dependent phototherapy. We reviewed the liposomal structures for delivery of photosensitizers, and introduced a novel class of phototransducing liposomes called "porphysomes". Porphysomes are self-assembled from high packing density of pyropheophorbide alpha-conjugated phospholipids, resulting in extreme self-quenching of porphyrin fluorescence and comparable optical absorption to gold nanoparticles for high photothermal efficiency. We demonstrated this self-assembly of porphyrin-lipid conjugates converts a singlet oxygen generating mechanism (photodynamic therapy PDT activity) of porphyrin to photothermal mechanism (photothermal therapy PTT activity). The efficacy of porphysome-enhanced PTT was then evaluated on two pre-clinical animal models. We validated porphysome-enabled focal PTT to treat orthotopic prostate cancer using MRI-guided focal laser placement to closely mimic the current clinic procedure. Furthermore, porphysome-enabled fluorescence-guided transbronchial PTT of lung cancer was demonstrated in rabbit orthotopic lung cancer models, which led to the development of an ultra-minimally invasive therapy for early-stage peripheral lung cancer. On the other hand, the nanostructure-mediated conversion of PDT to PTT can be switched back by nanoparticle dissociation. By incorporating folate-conjugated phospholipids into the formulation, porphysomes were internalized into cells rapidly via folate receptor-mediated endocytosis and resulted in efficient disruption of nanostructures, which turned back on the photodynamic activity of densely packed porphyrins, making a closed loop of conversion between PDT and PTT. The multimodal imaging and therapeutic features of porphysome make it ideal for future personalized cancer treatments.

  15. Method and apparatus for low temperature destruction of halogenated hydrocarbons

    DOEpatents

    Reagen, William Kevin; Janikowski, Stuart Kevin

    1999-01-01

    A method and apparatus for decomposing halogenated hydrocarbons are provided. The halogenated hydrocarbon is mixed with solvating agents and maintained in a predetermined atmosphere and at a predetermined temperature. The mixture is contacted with recyclable reactive material for chemically reacting with the recyclable material to create dehalogenated hydrocarbons and halogenated inorganic compounds. A feature of the invention is that the process enables low temperature destruction of halogenated hydrocarbons.

  16. Tapping the biotechnological potential of insect microbial symbionts: new insecticidal porphyrins.

    PubMed

    Martinez, Ana Flávia Canovas; de Almeida, Luís Gustavo; Moraes, Luiz Alberto Beraldo; Cônsoli, Fernando Luís

    2017-06-27

    The demand for sustainable agricultural practices and the limited progress toward newer and safer chemicals for use in pest control maintain the impetus for research and identification of new natural molecules. Natural molecules are preferable to synthetic organic molecules because they are biodegradable, have low toxicity, are often selective and can be applied at low concentrations. Microbes are one source of natural insecticides, and microbial insect symbionts have attracted attention as a source of new bioactive molecules because these microbes are exposed to various selection pressures in their association with insects. Analytical techniques must be used to isolate and characterize new compounds, and sensitive analytical tools such as mass spectrometry and high-resolution chromatography are required to identify the least-abundant molecules. We used classical fermentation techniques combined with tandem mass spectrometry to prospect for insecticidal substances produced by the ant symbiont Streptomyces caniferus. Crude extracts from this bacterium showed low biological activity (less than 10% mortality) against the larval stage of the fall armyworm Spodoptera frugiperda. Because of the complexity of the crude extract, we used fractionation-guided bioassays to investigate if the low toxicity was related to the relative abundance of the active molecule, leading to the isolation of porphyrins as active molecules. Porphyrins are a class of photoactive molecules with a broad range of bioactivity, including insecticidal. The active fraction, containing a mixture of porphyrins, induced up to 100% larval mortality (LD 50  = 37.7 μg.cm -2 ). Tandem mass-spectrometry analyses provided structural information for two new porphyrin structures. Data on the availability of porphyrins in 67 other crude extracts of ant ectosymbionts were also obtained with ion-monitoring experiments. Insect-associated bacterial symbionts are a rich source of bioactive compounds. Exploring

  17. Halogen Chemistry at North American Coastal Sites

    NASA Astrophysics Data System (ADS)

    Stutz, J.; Pikelnaya, O.; Laskin, A.; Sumner, A.; Jobson, B. T.; Finley, B.; Lawler, M.; Saltzman, E. S.; Pszenny, A. A.; Deegan, B.

    2007-12-01

    In recent years observational evidence has emerged that reactive halogen species (RHS), such as chlorine atoms, and bromine and iodine oxides, are present in coastal areas. Their chemistry can be significant as they catalytically destroy O3; oxidize hydrocarbons, dimethylsulfide, and S(IV); and modify NOx and HOx cycling. Despite their potential importance our observational database on RHS is still very limited. Most observations of RHS thus far have been made in clean areas and very few observations along the North American coast have been made. Here we will review our current understanding of RHS chemistry in both clean and polluted environments. Recent observations at coastal areas around the world will be discussed. We will also give an overview of an experiment performed by our group in Malibu, CA in October 2006 and present initial results. A suite of trace gases and environmental parameters, including halogen molecules, halogen oxides, Cl + VOC reaction products, aerosol composition, O3, NOx, CO, VOCs, meteorology, and radiation, were measured during a three week period. In addition, Cl + VOC reaction products were measured at two locations in urban Los Angeles. Clear evidence for the presence of various halogen species on the California coast was found. Observations during periods with relatively clean marine air and during times where our site was in the outflow of Los Angeles show the impact of pollution on coastal atmospheric chemistry. Our observations will be compared to earlier studies of halogen chemistry at coastal areas to further advance our understanding of halogen chemistry.

  18. A new class of halogen bonds that avoids the σ-hole

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Ma, Ning; Wang, Weizhou

    2012-04-01

    A new class of halogen bonds of the type X = Hal⋯Y has been investigated by using the density functional theory calculations. The strength of this new class of halogen bonds is in the range of 90-120 kcal/mol, which is greatly larger than that of the conventional halogen bond of the type X-Hal⋯Y. The geometry of this new class of halogen bonds is not determined by the halogen's positive σ-hole. Natural bond orbital analysis shows it is the n → π∗ interaction that determines the geometry of this new class of halogen bonds. Experimental results are in good agreement with the theoretical predictions.

  19. Bio-inspired cofacial Fe porphyrin dimers for efficient electrocatalytic CO2 to CO conversion: Overpotential tuning by substituents at the porphyrin rings

    PubMed Central

    Zahran, Zaki N.; Mohamed, Eman A.; Naruta, Yoshinori

    2016-01-01

    Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2. The binuclear Ni, Fe−containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO. The location of Ni and Fe at proper positions allows their cooperation for CO2 to CO conversion through a push−pull mechanism. Bio−inspired from CODHs, we used several cofacial porphyrin dimers with different substituents as suitable ligands for holding two Fe ions with suitable Fe−Fe separation distance to efficiently and selectively promote CO2 to CO conversion with high turnover frequencies, TOFs. The substituents on the porphyrin rings greatly affect the catalysis process. By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups. The Fe porphyrin dimers among reported catalysts are the most efficient ones for CO2 to CO conversion. Control experiments indicate that the high performance of the current CO2 to CO conversion catalysts is due to the presence of binuclear Fe centers at suitable Fe−Fe separation distance. PMID:27087483

  20. Urinary porphyrins as biomarkers for arsenic exposure among susceptible populations in Guizhou Province, China

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ng, J.C.; Wang, J.P.; Zheng, B.S.

    2005-08-07

    Coal from some areas in Guizhou Province contains elevated levels of arsenic. This has caused arsenicosis in individuals who use arsenic-contaminated coal for the purposes of heating, cooking and drying of food in poorly ventilated dwellings. The population at risk has been estimated to be approximately 200,000 people. We analyzed the porphyrin excretion profile using a HPLC method in urine samples collected from 113 villagers who lived in Xing Ren district, a coal-borne arsenicosis endemic area and from 30 villagers from Xing Yi where arsenicosis is not prevalent. Urinary porphyrins were higher in the arsenic exposed group than those inmore » the control group. The correlation between urinary arsenic and porphyrin concentrations demonstrated the effect of arsenic on heme biosynthesis resulting in increased porphyrin excretion. Both uroporphyrin and coproporphyrin III showed significant increases in the excretion profile of the younger age ({lt} 20 years) arsenic-exposed group, suggesting that porphyrins could be used as early warning biomarkers of chronic arsenic exposure in humans. Greater increases of urinary arsenic and porphyrins in women, children and older age groups who spend much of their time indoors suggest that they might be at a higher risk. Whether elevated porphyrins could predict adverse health effects associated with both cancer and non-cancer end-points in chronically arsenic-exposed populations need further investigation.« less

  1. Halogen-Mediated Conversion of Hydrocarbons to Commodities.

    PubMed

    Lin, Ronghe; Amrute, Amol P; Pérez-Ramírez, Javier

    2017-03-08

    Halogen chemistry plays a central role in the industrial manufacture of various important chemicals, pharmaceuticals, and polymers. It involves the reaction of halogens or halides with hydrocarbons, leading to intermediate compounds which are readily converted to valuable commodities. These transformations, predominantly mediated by heterogeneous catalysts, have long been successfully applied in the production of polymers. Recent discoveries of abundant conventional and unconventional natural gas reserves have revitalized strong interest in these processes as the most cost-effective gas-to-liquid technologies. This review provides an in-depth analysis of the fundamental understanding and applied relevance of halogen chemistry in polymer industries (polyvinyl chloride, polyurethanes, and polycarbonates) and in the activation of light hydrocarbons. The reactions of particular interest include halogenation and oxyhalogenation of alkanes and alkenes, dehydrogenation of alkanes, conversion of alkyl halides, and oxidation of hydrogen halides, with emphasis on the catalyst, reactor, and process design. Perspectives on the challenges and directions for future development in this exciting field are provided.

  2. Self-assembled novel multi-porphyrin micro-crystals as a photocatalyst for 2,4,6-trinitrotoluene degradation

    NASA Astrophysics Data System (ADS)

    Hikal, Walid M.

    In this thesis I have presented the findings of my research pursued during my Ph.D. study. Following the findings that 2,4,6-trinitrotoluene binds to porphyrins at room temperature and could be photoctalytically degraded using porphyrin solutions and visible light, the purpose of this work was to determine the nature of the binding between the two species and develop a solid porphyrin-based photocatalyst for TNT degradation. C1TPP porphyrin is found to be able to bind to TNT via 1.94 kcal/mole hydrogen bonds at room temperature and hydrophobic bonds at higher temperatures. Photocatalytic solid porphyrin crystalline structures have been developed using two oppositely charged, commercially available, and low cost porphyrins in presence and absence of PAMAM generation 4 (G4) dendrimer, by self-assembly at room temperature without acidification. Solid porphyrin crystals were characterized by means of optical microscopy, UV-visible spectroscopy, fluorescence spectroscopy, and powder X-ray diffraction. A hypothetical model for the structure of the crystals is proposed. The porphyrin crystals show photocatalytic capabilities; illumination of the crystals in a 2,4,6-trinitrotoluene solution by visible light results in degradation of TNT and the intermediates have been determined using high pressure liquid chromatography (HPLC) and gas chromatography (GC).

  3. Hepatitis C virus core protein triggers abnormal porphyrin metabolism in human hepatocellular carcinoma cells.

    PubMed

    Nakano, Takafumi; Moriya, Kyoji; Koike, Kazuhiko; Horie, Toshiharu

    2018-01-01

    Porphyria cutanea tarda (PCT), the most common of the human porphyrias, arises from a deficiency of uroporphyrinogen decarboxylase. Studies have shown a high prevalence of hepatitis C virus (HCV) infection in patients with PCT. While these observations implicate HCV infection as a risk factor for PCT pathogenesis, the mechanism of interaction between the virus and porphyrin metabolism is unknown. This study aimed to assess the effect of HCV core protein on intracellular porphyrin metabolism to elucidate the link between HCV infection and PCT. The accumulation and excretion of porphyrins after treatment with 5-aminolevulinic acid, a porphyrin precursor, were compared between cells stably expressing HCV core protein and controls. Cells expressing HCV core protein had lower amounts of intracellular protoporphyrin IX and heme and had higher amounts of excreted coproporphyrin III, the oxidized form of coproporphyrinogen III, compared with controls. These observations suggest that HCV core protein affects porphyrin metabolism and facilitates the export of excess coproporphyrinogen III and/or coproporphyrin III, possibly via porphyrin transporters. Real-time PCR analysis revealed that the presence of HCV core protein increased the mRNA expression of porphyrin exporters ABCG2 and FLVCR1. Western blot analysis showed a higher expression level of FLVCR1, but not ABCG2, as well as a higher expression level of mature ALAS1, which is the rate-limiting enzyme in the heme synthesis pathway, in HCV core protein-expressing cells compared with controls. The data indicate that HCV core protein induced abnormal intracellular porphyrin metabolism, with an over-excretion of coproporphyrin III. These findings may partially account for the susceptibility of HCV-infected individuals to PCT development.

  4. Synthesis of Phosphorescent Asymmetrically π-Extended Porphyrins for Two-Photon Applications

    PubMed Central

    2015-01-01

    Significant effort has been directed in recent years toward porphyrins with enhanced two-photon absorption (2PA). However, the properties of their triplet states, which are central to many applications, have rarely been examined in parallel. Here we report the synthesis of asymmetrically π-extended platinum(II) and palladium(II) porphyrins, whose 2PA into single-photon-absorbing states is enhanced as a result of the broken center-of-inversion symmetry and whose triplet states can be monitored by room-temperature phosphorescence. 5,15-Diaryl-syn-dibenzoporphyrins (DBPs) and syn-dinaphthoporphyrins (DNPs) were synthesized by [2 + 2] condensation of the corresponding dipyrromethanes and subsequent oxidative aromatization. Butoxycarbonyl groups on the meso-aryl rings render these porphyrins well-soluble in a range of organic solvents, while 5,15-meso-aryl substitution causes minimal nonplanar distortion of the macrocycle, ensuring high triplet emissivity. A syn-DBP bearing four alkoxycarbonyl groups in the benzo rings and possessing a large static dipole moment was also synthesized. Photophysical properties (2PA brightness and phosphorescence quantum yields and lifetimes) of the new porphyrins were measured, and their ground-state structures were determined by DFT calculations and/or X-ray analysis. The developed synthetic methods should facilitate the construction of π-extended porphyrins for applications requiring high two-photon triplet action cross sections. PMID:25157580

  5. A charge-stabilizing, multimodular, ferrocene-bis(triphenylamine)-zinc-porphyrin-fullerene polyad.

    PubMed

    Wijesinghe, Channa A; El-Khouly, Mohamed E; Zandler, Melvin E; Fukuzumi, Shunichi; D'Souza, Francis

    2013-07-15

    A novel multimodular donor-acceptor polyad featuring zinc porphyrin, fullerene, ferrocene, and triphenylamine entities was designed, synthesized, and studied as a charge-stabilizing, photosynthetic-antenna/reaction-center mimic. The ferrocene and fullerene entities, covalently linked to the porphyrin ring, were distantly separated to accomplish the charge-separation/hole-migration events leading to the creation of a long-lived charge-separated state. The geometry and electronic structures of the newly synthesized compound was deduced by B3LYP/3-21G(*) optimization, while the energy levels for different photochemical events was established using data from the optical absorption and emission, and electrochemical studies. Excitation of the triphenylamine entities revealed singlet-singlet energy transfer to the appended zinc porphyrin. As predicted from the energy levels, photoinduced electron transfer from both the singlet and triplet excited states of the zinc porphyrin to fullerene followed by subsequent hole migration involving ferrocene was witnessed from the transient absorption studies. The charge-separated state persisted for about 8.5 μs and was governed by the distance between the final charge-transfer product, that is, a species involving a ferrocenium cation and a fullerene radical anion, with additional influence from the charge-stabilizing triphenylamine entities located on the zinc-porphyrin macrocycle. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Electrochemical detection of dopamine using porphyrin-functionalized graphene.

    PubMed

    Wu, Li; Feng, Lingyan; Ren, Jinsong; Qu, Xiaogang

    2012-04-15

    A new type of porphyrin-functionalized graphene was synthesized and used for highly selective and sensitive detection of dopamine (DA). The aromatic π-π stacking and electrostatic attraction between positively-charged dopamine and negatively-charged porphyrin-modified graphene can accelerate the electron transfer whereas weakening ascorbic acid (AA) and uric acid (UA) oxidation on the porphyrin-functionalized graphene-modified electrode. Differential pulse voltammetry was used for electrochemical detection, the separation of the oxidation peak potentials for AA-DA, DA-UA and UA-AA is about 188 mV, 144 mV and 332 mV, which allows selectively determining DA. The detection limit of DA can be as low as 0.01 μM. More importantly, the sensor we presented can detect DA in the presence of large excess of ascorbic acid and uric acid. With good sensitivity and selectivity, the present method was applied to the determination of DA in real hydrochloride injection sample, human urine and serum samples, respectively, and the results was satisfactory. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. GEOCHEMICAL AND MICROBIAL REACTIONS AFFECTING THE LONG-TERM PERFORMANCE OF IN SITU 'IRON BARRIERS'

    EPA Science Inventory

    The in situ application of granular iron (Fe0) has become popular for the destruction of halogenated organic compounds for the immobilization of specific metals in groundwater. However, a knowledge gap exists concerning the long-term performance of the Fe0-barriers. The corrosi...

  8. Treatment of halogen-containing waste and other waste materials

    DOEpatents

    Forsberg, Charles W.; Beahm, Edward C.; Parker, George W.

    1997-01-01

    A process for treating a halogen-containing waste material. The process provides a bath of molten glass containing a sacrificial metal oxide capable of reacting with a halogen in the waste material. The sacrificial metal oxide is present in the molten glass in at least a stoichiometric amount with respect to the halogen in the waste material. The waste material is introduced into the bath of molten glass to cause a reaction between the halogen in the waste material and the sacrificial metal oxide to yield a metal halide. The metal halide is a gas at the temperature of the molten glass. The gaseous metal halide is separated from the molten glass and contacted with an aqueous scrubber solution of an alkali metal hydroxide to yield a metal hydroxide or metal oxide-containing precipitate and a soluble alkali metal halide. The precipitate is then separated from the aqueous scrubber solution. The molten glass containing the treated waste material is removed from the bath as a waste glass. The process of the invention can be used to treat all types of waste material including radioactive wastes. The process is particularly suited for separating halogens from halogen-containing wastes.

  9. Early events in 2,4,6-trinitrotoluene (TNT) degradation by porphyrins: binding of TNT to porphyrin by hydrophobic and hydrogen bonds.

    PubMed

    Hikal, Walid M; Harmon, H James

    2008-06-15

    The interaction of meso-tri(4-sulfonatophenyl)mono(4-carboxyphenyl) porphyrin (C1TPP) with 2,4,6-trinitrotoluene (TNT) has been explored by UV-vis and fluorescence spectroscopy. The influence of temperature on the interaction has also been studied. C1TPP binds to TNT at pH 7.0 at room temperature via 1.94 kcal/mole hydrogen bonds with absorbance loss at 412-413 nm and the appearance of a new peak at 422-424 nm. The hydrogen binding of TNT to C1TPP was confirmed by the dissolution of the complex upon the addition of urea. Increasing the temperature results in the appearance of a new absorbance peak at 540 nm and absorbance loss at 515 nm with activation energy of 29.7 kcal/mole in the range of the hydrophobic bond energy. This suggests the hydrophobic bonding of TNT with the pyrrole nitrogens in the porphyrin. Increasing the concentration of the TNT in the solution quenches the fluorescence of the porphyrin following the Stern-Volmer equation. The association constants calculated from absorbance and fluorescence are expectedly similar.

  10. Molecular structure, magnetic properties, cyclic voltammetry of the low-spin iron(III) Bis(4-ethylaniline) complex with the para-chloro substituted meso-tetraphenylporphyrin

    NASA Astrophysics Data System (ADS)

    Dhifaoui, Selma; Mchiri, Chadlia; Quatremare, Pierre; Marvaud, Valérie; Bujacz, Anna; Nasri, Habib

    2018-02-01

    In this study, the preparation of a new iron(III) hexacoordinated metalloporphyrin namely the bis(4-ethylaniline){meso-tetra(para-chlorophenyl)porphyrinato}iron(III) triflate hemi-4-ethylaniline monohydrate with the formula [FeIII(TClPP)(PhEtNH2)2]SO3CF3•1/2PhEtNH2•H2O (I) was reported. This is the first example of an iron(III) metalloporphyrin bis(primary amine) with an aryl group adjacent to the amino group. This species was characterized by elemental, spectroscopic analysis including UV-visible and IR data, cyclic voltammetry, SQUID measurements and X-ray molecular structure. The mean equatorial distance between the iron(III) and the nitrogens of the porphyrin is appropriate for a low-spin (S = 1/2) iron(III) porphyrin complex. The magnetic data confirm the low-spin state of our ferric derivative while the cyclic voltammetry indicates a shift of the half potential E1/2[Fe(III)/Fe(II)] of complex (I) toward more negative value. In the crystal of (I), the [FeIII(TClPP)(PhEtNH2)2]+ ions, the triflate counterions and the water molecules are involved in a number of O__H⋯O, N__H⋯O, C-H⋯O and C__H⋯π intermolecular interactions forming a three-dimension network.

  11. The effect of porphyrins on normal and transformed mouse cell lines in the presence of visible light.

    PubMed

    Tita, S P; Perussi, J R

    2001-10-01

    Photodynamic therapy consists of the uptake of a photosensitizing dye, often a porphyrin, by tumor tissue and subsequent irradiation of the tumor with visible light of an appropriate wavelength matched to the absorption spectrum of the photosensitizing dye. This class of molecules produces reactive oxygen species when activated by light, resulting in a direct or indirect cytotoxic effect on the target cells. Photodynamic therapy has been used in the treatment of cancer but the technology has a potential for the treatment of several disease conditions mainly because of its selectivity. However, it is not clear why the porphyrins are retained preferentially by abnormal tissue. This paper describes a study of the effect of the association of porphyrin and visible light on two mouse fibroblast cell lines: A31, normal cells and B61, an EJ-ras transformed variant of A31. Two water-soluble porphyrins were used, a positively charged one, tetra(N-methyl-4-pyridyl)porphyrin chloride, and a negatively charged one, tetra(4-sulfonatophenyl)porphyrin-Na salt (TPPS4) in order to assess the effect on cell survival. The results suggest that the B61 cell line is more sensitive to incubation with the anionic porphyrin (TPPS4) followed by light irradiation and that the anionic porphyrin is more efficient in killing the cells than the cationic porphyrin.

  12. Halogen-free boron based electrolyte solution for rechargeable magnesium batteries

    NASA Astrophysics Data System (ADS)

    Zhu, Jinjie; Guo, Yongsheng; Yang, Jun; Nuli, Yanna; Zhang, Fan; Wang, Jiulin; Hirano, Shin-ichi

    2014-02-01

    All halogen containing electrolytes for Mg battery are apt to corrode conventional metal current collectors. In this paper, a new type of halogen-free boron based electrolyte (Mg[Mes3BPh]2/THF) is designed and prepared. Electrochemical tests show that this electrolyte system possesses high ion conductivity (1.5 × 10-3 S cm-1) and good Mg deposition-dissolution reversibility. More importantly, the same electrochemical window (2.6 V vs. Mg RE) of the electrolyte on Pt and stainless steel electrodes indicates that halogen-free electrolyte indeed lessens the corrosion to conventional metal current collectors. The surface morphologies of stainless steel, aluminum and copper are further observed after their anodic potentiostatic polarization in 0.25 mol L-1 Mg[Mes3BPh]2/THF electrolyte solution for 2 days. A comparison with halogen containing electrolytes proves that the presence of halogen in electrolyte is the reason for corrosion. This work provides a stepping stone for developing new halogen-free electrolyte systems for rechargeable Mg batteries.

  13. Electronic Spectroscopy of Phthalocyanine and Porphyrin Derivatives in Superfluid Helium Nanodroplets.

    PubMed

    Slenczka, Alkwin

    2017-07-25

    Phthalocyanine and porphyrin were among the first organic compounds investigated by means of electronic spectroscopy in superfluid helium nanodroplets. Superfluid helium nanodroplets serve as a very gentle host system for preparing cold and isolated molecules. The uniqueness of helium nanodroplets is with respect to the superfluid phase which warrants the vanishing viscosity and, thus, minimal perturbation of the dopant species at a temperature as low as 0.37 K. These are ideal conditions for the study of molecular spectra in order to analyze structures as well as dynamic processes. Besides the investigation of the dopant species itself, molecular spectroscopy in helium droplets provides information on the helium droplet and in particular on microsolvation. This article, as part of a special issue on phthalocyanines and porphyrins, reviews electronic spectroscopy of phthalocyanine and porphyrin compounds in superfluid helium nanodroplets. In addition to the wide variety of medical as well as technical and synthetical aspects, this article discusses electronic spectroscopy of phthalocyanines and porphyrins in helium droplets in order to learn about both the dopant and the helium environment.

  14. Investigating Planetary Volatile Accretion Mechanisms Using the Halogens

    NASA Astrophysics Data System (ADS)

    Ballentine, C. J.; Clay, P. L.; Burgess, R.; Busemann, H.; Ruzié, L.; Joachim, B.; Day, J. M.

    2014-12-01

    Depletion of the volatile elements in the Earth relative to the CI chondrites is roughly correlated with volatility, or decreasing condensation temperature. For the heavy halogen group elements (Cl, Br and I), volatility alone does not account for their apparent depletion, which early data has suggested is far greater than predicted [1-2]. Such depletion has been used to argue for the preferential loss of halogens by, amongst other processes, impact-driven erosive loss from Earth's surface [2]. Little consensus exists as to why the halogens should exhibit such preferential behavior during accretionary processes. Early efforts to constrain halogen abundance and understand their behavior in both Earth and planetary materials [3-6] have been hampered by their typically low abundance (ppb level) in most geologic materials. We present the results of halogen analysis of 23 chondrite samples, selected to represent diverse groups and petrologic type. Halogen abundances were measured by neutron irradiation noble gas mass spectrometry (NI-NGMS). Significant concentration heterogeneity is observed within some samples. However, a single Br/Cl and I/Cl ratio of 1.9 ± 0.2 (x 10-3) and 335 ± 10 (x 10-6) can be defined for carbonaceous chondrites with a good correlation between Br and Cl (R2 = 0.97) and between I and Cl (R2 = 0.84). Ratios of I/Cl overlap with terrestrial estimates of Bulk Silicate Earth and Mid Ocean Ridge Basalts. Similarly, good correlations are derived for enstatite (E) chondrites and a sulfide- and halogen- rich subset of E-chondrites. Chlorine abundances of CI (Orgueil) in this study are lower by factor of ~ 3 than the value of ~ 700 ppm Cl (compilation in [1]). Our results are similar to early discarded low values for Ivuna and Orgueil from [5,6] and agree more closely with values for CM chondrites. Halogens may not be as depleted in Earth as previously suggested, or a high degree of heterogeneity in the abundance of these volatile elements in

  15. Light-activated nanotube-porphyrin conjugates as effective antiviral agents

    NASA Astrophysics Data System (ADS)

    Banerjee, Indrani; Douaisi, Marc P.; Mondal, Dhananjoy; Kane, Ravi S.

    2012-03-01

    Porphyrins have been used for photodynamic therapy (PDT) against a wide range of targets like bacteria, viruses and tumor cells. In this work, we report porphyrin-conjugated multi-walled carbon nanotubes (NT-P) as potent antiviral agents. Specifically, we used Protoporphyrin IX (PPIX), which we attached to acid-functionalized multi-walled carbon nanotubes (MWNTs). We decided to use carbon nanotubes as scaffolds because of their ease of recovery from a solution through filtration. In the presence of visible light, NT-P was found to significantly reduce the ability of Influenza A virus to infect mammalian cells. NT-P may be used effectively against influenza viruses with little or no chance of them developing resistance to the treatment. Furthermore, NT-P can be easily recovered through filtration which offers a facile strategy to reuse the active porphyrin moiety to its fullest extent. Thus NT-P conjugates represent a new approach for preparing ex vivo reusable antiviral agents.

  16. Functionalization of Carbon Spheres with a Porphyrin-Ferrocene Dyad.

    PubMed

    Possanza, Fabio; Limosani, Francesca; Tagliatesta, Pietro; Zanoni, Robertino; Scarselli, Manuela; Ciotta, Erica; Pizzoferrato, Roberto

    2018-05-21

    Meso-tetraphenylporphyrin connected with a ferrocene molecule in the beta-position of the macrocycle through a triple carbon-carbon bond has been bound to carbon spheres using the Prato-Maggini reaction. The ethynyl or/and phenylene ethynylene subunits were chosen as a linking bridge to give a high conjugation degree between the donor (i. e., ferrocene), the photoactive compound (i. e., porphyrin), and the acceptor (i. e., carbon spheres). The molecular bridges have been directly linked to the beta-pyrrole positions of the porphyrin ring, generating a new example of a long-range donor-acceptor system. Steady-state fluorescence studies together with Raman and XPS measurements helped understanding the chemical and physical properties of the porphyrin ring in the new adduct. The spectroscopic characteristics were also compared with those obtained from a similar compound bearing fullerene instead of carbon spheres. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Nanoarchitectonics with Porphyrin Functionalized DNA

    PubMed Central

    2017-01-01

    Conspectus DNA is well-known as bearer of the genetic code. Since its structure elucidation nearly seven decades ago by Watson, Crick, Wilkins, and Franklin, much has been learned about its detailed structure, function, and genetic coding. The development of automated solid-phase synthesis, and with it the availability of synthetic DNA with any desired sequence in lengths of up to hundreds of bases in the best case, has contributed much to the advancement of the field of DNA research. In addition, classic organic synthesis has allowed introduction of a very large number of modifications in the DNA in a sequence specific manner, which have initially been targeted at altering the biological function of DNA. However, in recent years DNA has become a very attractive scaffold in supramolecular chemistry, where DNA is taken out of its biological role and serves as both stick and glue molecule to assemble novel functional structures with nanometer precision. The attachment of functionalities to DNA has led to the creation of supramolecular systems with applications in light harvesting, energy and electron transfer, sensing, and catalysis. Functional DNA is clearly having a significant impact in the field of bioinspired nanosystems. Of particular interest is the use of porphyrins in supramolecular chemistry and bionanotechnology, because they are excellent functional groups due to their electronic properties that can be tailored through chemical modifications of the aromatic core or through insertion of almost any metal of the periodic table into the central cavity. The porphyrins can be attached either to the nucleobase, to the phosphate group, or to the ribose moiety. Additionally, noncovalent templating through Watson–Crick base pairing forms an alternative and attractive approach. With this, the combination of two seemingly simple molecules gives rise to a highly complex system with unprecedented possibilities for modulation of function, and with it applications

  18. Binary ionic porphyrin nanosheets: electronic and light-harvesting properties regulated by crystal structure

    NASA Astrophysics Data System (ADS)

    Tian, Yongming; M. Beavers, Christine; Busani, Tito; Martin, Kathleen E.; Jacobsen, John L.; Mercado, Brandon Q.; Swartzentruber, Brian S.; van Swol, Frank; Medforth, Craig J.; Shelnutt, John A.

    2012-02-01

    Crystalline solids self-assembled from anionic and cationic porphyrins provide a new class of multifunctional optoelectronic micro- and nanomaterials. A 1 : 1 combination of zinc(ii) tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) and tin(iv) tetra(N-methyl-4-pyridiniumyl)porphyrin (SnTNMePyP) gives porphyrin nanosheets with high aspect ratios and varying thickness. The room temperature preparation of the nanosheets has provided the first X-ray crystal structure of a cooperative binary ionic (CBI) solid. The unit cell contains one and one-half molecules of aquo-ZnTPPS4- (an electron donor) and three half molecules of dihydroxy-SnTNMePyP4+ (an electron acceptor). Charge balance in the solid is reached without any non-porphyrinic ions, as previously determined for other CBI nanomaterials by non-crystallographic means. The crystal structure reveals a complicated molecular arrangement with slipped π-π stacking only occurring in isolated dimers of one of the symmetrically unique zinc porphyrins. Consistent with the crystal structure, UV-visible J-aggregate bands indicative of exciton delocalization and extended π-π stacking are not observed. XRD measurements show that the structure of the Zn/Sn nanosheets is distinct from that of Zn/Sn four-leaf clover-like CBI solids reported previously. In contrast with the Zn/Sn clovers that do exhibit J-aggregate bands and are photoconductive, the nanosheets are not photoconductive. Even so, the nanosheets act as light-harvesting structures in an artificial photosynthesis system capable of reducing water to hydrogen but not as efficiently as the Zn/Sn clovers.Crystalline solids self-assembled from anionic and cationic porphyrins provide a new class of multifunctional optoelectronic micro- and nanomaterials. A 1 : 1 combination of zinc(ii) tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) and tin(iv) tetra(N-methyl-4-pyridiniumyl)porphyrin (SnTNMePyP) gives porphyrin nanosheets with high aspect ratios and varying thickness. The room

  19. A tightly coupled linear array of perylene, bis(porphyrin), and phthalocyanine units that functions as a photoinduced energy-transfer cascade

    PubMed

    Miller; Lammi; Prathapan; Holten; Lindsey

    2000-10-06

    We have prepared a linear array of chromophores consisting of a perylene input unit, a bis(free base porphyrin) transmission unit, and a free base phthalocyanine output unit for studies in artificial photosynthesis and molecular photonics. The synthesis involved four stages: (1) a rational synthesis of trans-AB2C-porphyrin building blocks each bearing one meso-unsubstituted position, (2) oxidative, meso,meso coupling of the zinc porphyrin monomers to afford a bis(zinc porphyrin) bearing one phthalonitrile group and one iodophenyl group, (3) preparation of a bis(porphyrin)-phthalocyanine array via a mixed cyclization involving the bis(free base porphyrin) and 4-tert-butylphthalonitrile, and (4) Pd-mediated coupling of an ethynylperylene to afford a perylene-bis(porphyrin)-phthalocyanine linear array. The perylene-bis(porphyrin)-phthalocyanine array absorbs strongly across the visible spectrum. Excitation at 490 nm, where the perylene absorbs preferentially, results in fluorescence almost exclusively from the phthalocyanine (phi(f) = 0.78). The excited phthalocyanine forms with time constants of 2 ps (90%) and 13 ps (10%). The observed time constants resemble those of corresponding phenylethyne-linked dyads, including a perylene-porphyrin (< or = 0.5 ps) and a porphyrin-phthalocyanine (1.1 ps (70%) and 8 ps (30%)). The perylene-bis(porphyrin)-phthalocyanine architecture exhibits efficient light-harvesting properties and rapid funneling of energy in a cascade from perylene to bis(porphyrin) to phthalocyanine.

  20. Porphyrin-induced photogeneration of hydrogen peroxide determined using the luminol chemiluminescence method in aqueous solution: A structure-activity relationship study related to the aggregation of porphyrin.

    PubMed

    Komagoe, Keiko; Katsu, Takashi

    2006-02-01

    A luminol chemiluminescence method was used to evaluate the porphyrin-induced photogeneration of hydrogen peroxide (H2O2). This method enabled us to detect H202 in the presence of a high concentration of porphyrin, which was not possible using conventional colorimetry. The limit of detection was about 1 microM. We compared the ability to generate H2O2, using uroporphyrin (UP), hexacarboxylporphyrin (HCP), coproporphyrin (CP), hematoporphyrin (HP), mesoporphyrin (MP), and protoporphyrin (PP). The amount of H2O2 photoproduced was strongly related to the state of the porphyrin in the aqueous solution. UP and HCP, which existed predominantly in a monomeric form, had a good ability to produce H2O2. HP and MP, existing as dimers, showed weak activity. CP, forming a mixture of monomer and dimer, had a moderate ability to produce H2O2. PP, which was highly aggregated, had a good ability. These results demonstrated that the efficiency of porphyrins to produce H2O2 was strongly dependent on their aggregated form, and the dimer suppressed the production of H2O2.

  1. Non-sensitized selective photochemical reduction of CO2 to CO under visible light with an iron molecular catalyst.

    PubMed

    Rao, Heng; Bonin, Julien; Robert, Marc

    2017-03-02

    A substituted tetraphenyl iron porphyrin, bearing positively charged trimethylammonio groups at the para position of each phenyl ring, demonstrates its ability as a homogeneous molecular catalyst to selectively reduce CO 2 to CO under visible light irradiation in organic media without the assistance of a sensitizer and no competitive hydrogen evolution for several days.

  2. Treatment of halogen-containing waste and other waste materials

    DOEpatents

    Forsberg, C.W.; Beahm, E.C.; Parker, G.W.

    1997-03-18

    A process is described for treating a halogen-containing waste material. The process provides a bath of molten glass containing a sacrificial metal oxide capable of reacting with a halogen in the waste material. The sacrificial metal oxide is present in the molten glass in at least a stoichiometric amount with respect to the halogen in the waste material. The waste material is introduced into the bath of molten glass to cause a reaction between the halogen in the waste material and the sacrificial metal oxide to yield a metal halide. The metal halide is a gas at the temperature of the molten glass. The gaseous metal halide is separated from the molten glass and contacted with an aqueous scrubber solution of an alkali metal hydroxide to yield a metal hydroxide or metal oxide-containing precipitate and a soluble alkali metal halide. The precipitate is then separated from the aqueous scrubber solution. The molten glass containing the treated waste material is removed from the bath as a waste glass. The process of the invention can be used to treat all types of waste material including radioactive wastes. The process is particularly suited for separating halogens from halogen-containing wastes. 3 figs.

  3. [Heme-iron in the human body].

    PubMed

    Balla, József; Balla, György; Lakatos, Béla; Jeney, Viktória; Szentmihályi, Klára

    2007-09-09

    Iron is essential for all living organism, although in excess amount it is dangerous via catalyzing the formation of reactive oxygen species. Absorption of iron is strictly controlled resulting in a fine balance of iron-loss and iron-uptake. In countries where the ingestion of heme-iron is significant by meal, great part of iron content in the body originates from heme. Heme derived from food is absorbed by a receptor-mediated manner by enterocytes of small intestine then it is degraded in a reaction catalyzed by heme oxygenase. Iron released from the porphyrin ring leaves enterocytes as transferrin associated iron. Prosthetic group of several proteins contains heme, therefore, it is synthesized by all cells. One of the most significant heme proteins is hemoglobin which transports oxygen in the erythrocytes. Hemoglobin released from erythrocyte during intravascular hemolysis binds to haptoglobin and is taken up by cells of the monocyte-macrophage lineage. Oxidation of hemoglobin (ferro) to methemoglobin (ferri) is inhibited by the structure of hemoglobin although it is not hindered. Superoxide anion is also formed in the reaction that initiates further free radical reactions. In contrast to ferrohemoglobin, methemoglobin readily releases heme, therefore, oxidation of hemoglobin drives the formation of free heme in plasma. Heme binds to a plasma protein, hemopexin, and is internalized by cells of monocyte-macrophage lineage in a receptor-mediated manner, then degraded in reaction catalysed by heme oxygenase. Heme is also taken up by plasma lipoproteins and endothelial cells leading to oxidation of LDL and subsequent endothelial cell damage. The purpose of this work was to summarize the processes related to heme.

  4. Femtosecond fluorescence dynamics of porphyrin in solution and solid films: the effects of aggregation and interfacial electron transfer between porphyrin and TiO2.

    PubMed

    Luo, Liyang; Lo, Chen-Fu; Lin, Ching-Yao; Chang, I-Jy; Diau, Eric Wei-Guang

    2006-01-12

    The excited-state relaxation dynamics of a synthetic porphyrin, ZnCAPEBPP, in solution, coated on a glass substrate as solid films, mixed with PMMA and coated on a glass substrate as solid films, and sensitized on nanocrystalline TiO2 films were investigated by using femtosecond fluorescence up-conversion spectroscopy with excitation in the Soret band, S2. We found that the S2--> S1 electronic relaxation of ZnCAPEBPP in solution and on PMMA films occurs in 910 and 690 fs, respectively, but it becomes extremely rapid, <100 fs, in solid films and TiO2 films due to formation of porphyrin aggregates. When probed in the S1 state of porphyrin, the fluorescence transients of the solid films show a biphasic kinetic feature with the rapid and slow components decaying in 1.9-2.4 and 19-26 ps, respectively. The transients in ZnCAPEBPP/TiO2 films also feature two relaxation processes but they occur on different time scales, 100-300 fs and 0.8-4.1 ps, and contain a small offset. According to the variation of relaxation period as a function of molecular density on a TiO2 surface, we assigned the femtosecond component of the TiO2 films as due to indirect interfacial electron transfer through a phenylethynyl bridge attached to one of four meso positions of the porphyrin ring, and the picosecond component arising from intermolecular energy transfer among porphyrins. The observed variation of aggregate-induced relaxation periods between solid and TiO2 films is due mainly to aggregation of two types: J-type aggregation is dominant in the former case whereas H-type aggregation prevails in the latter case.

  5. Method for halogenating or radiohalogenating a chemical compound

    DOEpatents

    Kabalka, George W.

    2006-05-09

    A method for obtaining a halogenated organic compound, whereby an organotrifluoroborate compound is reacted with a halide ion in the presence of an oxidizing agent to produce the corresponding halogenated organic compound. The method may be used for producing radiohalogenated organic compounds.

  6. The Halogen Bond in the Design of Functional Supramolecular Materials: Recent Advances

    PubMed Central

    2013-01-01

    Halogen bonding is an emerging noncovalent interaction for constructing supramolecular assemblies. Though similar to the more familiar hydrogen bonding, four primary differences between these two interactions make halogen bonding a unique tool for molecular recognition and the design of functional materials. First, halogen bonds tend to be much more directional than (single) hydrogen bonds. Second, the interaction strength scales with the polarizability of the bond-donor atom, a feature that researchers can tune through single-atom mutation. In addition, halogen bonds are hydrophobic whereas hydrogen bonds are hydrophilic. Lastly, the size of the bond-donor atom (halogen) is significantly larger than hydrogen. As a result, halogen bonding provides supramolecular chemists with design tools that cannot be easily met with other types of noncovalent interactions and opens up unprecedented possibilities in the design of smart functional materials. This Account highlights the recent advances in the design of halogen-bond-based functional materials. Each of the unique features of halogen bonding, directionality, tunable interaction strength, hydrophobicity, and large donor atom size, makes a difference. Taking advantage of the hydrophobicity, researchers have designed small-size ion transporters. The large halogen atom size provided a platform for constructing all-organic light-emitting crystals that efficiently generate triplet electrons and have a high phosphorescence quantum yield. The tunable interaction strengths provide tools for understanding light-induced macroscopic motions in photoresponsive azobenzene-containing polymers, and the directionality renders halogen bonding useful in the design on functional supramolecular liquid crystals and gel-phase materials. Although halogen bond based functional materials design is still in its infancy, we foresee a bright future for this field. We expect that materials designed based on halogen bonding could lead to

  7. Scientific conferences: A big hello to halogen bonding

    NASA Astrophysics Data System (ADS)

    Erdelyi, Mate

    2014-09-01

    Halogen bonding connects a wide range of subjects -- from materials science to structural biology, from computation to crystal engineering, and from synthesis to spectroscopy. The 1st International Symposium on Halogen Bonding explored the state of the art in this fast-growing field of research.

  8. Structure Optimization of 21,23-Core-Modified Porphyrins Absorbing Long-Wavelength Light as Potential Photosensitizers Against Breast Cancer Cells

    DTIC Science & Technology

    2007-04-01

    the core nitrogen atom(s) of natural porphyrins with heavy atoms such as S, Se, and Te provides a red -shift in their absorption spectra [4- 7]. The...shown in red , b in green and c in blue Copyright © 2007 Society of Porphyrins & Phthalocyanines J. Porphyrins Phthalocyanines 2007; 11: 1-8 Y. YOU ET AL...shown in red , b in green and c in blue Copyright © 2007 Society of Porphyrins & Phthalocyanines J. Porphyrins Phthalocyanines 2007; 11: 1-8

  9. Long-lived, charge-shift states in heterometallic, porphyrin-based dendrimers formed via click chemistry.

    PubMed

    Le Pleux, Loïc; Pellegrin, Yann; Blart, Errol; Odobel, Fabrice; Harriman, Anthony

    2011-05-26

    A series of multiporphyrin clusters has been synthesized and characterized in which there exists a logical gradient for either energy or electron transfer between the porphyrins. A central free-base porphyrin (FbP), for example, is equipped with peripheral zinc(II) porphyrins (ZnP) which act as ancillary light harvesters and transfer excitation energy to the FbP under visible light illumination. Additional energy-transfer steps occur at the triplet level, and the series is expanded by including magnesium(II) porphyrins and/or tin(IV) porphyrins as chromophores. Light-induced electron transfer is made possible by incorporating a gold(III) porphyrin (AuP(+)) into the array. Although interesting by themselves, these clusters serve as control compounds by which to understand the photophysical processes occurring within a three-stage dendrimer comprising an AuP(+) core, a second layer formed from four FbP units, and an outer layer containing 12 ZnP residues. Here, illumination into a peripheral ZnP leads to highly efficient electronic energy transfer to FbP, followed by charge transfer to the central AuP(+). Charge recombination within the resultant charge-shift state is intercepted by secondary hole transfer to the ZnP, which occurs with a quantum yield of around 20%. The final charge-shift state survives for some microseconds in fluid solution at room temperature.

  10. Monomeric Yeast Frataxin is an Iron-Binding Protein

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cook,J.; Bencze, K.; Jankovic, A.

    Friedreich's ataxia, an autosomal cardio- and neurodegenerative disorder that affects 1 in 50 000 humans, is caused by decreased levels of the protein frataxin. Although frataxin is nuclear-encoded, it is targeted to the mitochondrial matrix and necessary for proper regulation of cellular iron homeostasis. Frataxin is required for the cellular production of both heme and iron-sulfur (Fe-S) clusters. Monomeric frataxin binds with high affinity to ferrochelatase, the enzyme involved in iron insertion into porphyrin during heme production. Monomeric frataxin also binds to Isu, the scaffold protein required for assembly of Fe-S cluster intermediates. These processes (heme and Fe-S cluster assembly)more » share requirements for iron, suggesting that monomeric frataxin might function as the common iron donor. To provide a molecular basis to better understand frataxin's function, we have characterized the binding properties and metal-site structure of ferrous iron bound to monomeric yeast frataxin. Yeast frataxin is stable as an iron-loaded monomer, and the protein can bind two ferrous iron atoms with micromolar binding affinity. Frataxin amino acids affected by the presence of iron are localized within conserved acidic patches located on the surfaces of both helix-1 and strand-1. Under anaerobic conditions, bound metal is stable in the high-spin ferrous state. The metal-ligand coordination geometry of both metal-binding sites is consistent with a six-coordinate iron-(oxygen/nitrogen) based ligand geometry, surely constructed in part from carboxylate and possibly imidazole side chains coming from residues within these conserved acidic patches on the protein. On the basis of our results, we have developed a model for how we believe yeast frataxin interacts with iron.« less

  11. Monomeric Yeast Frataxin is an Iron Binding Protein†

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cook, J.; Bencze, K; Jankovic, A

    Friedreich's ataxia, an autosomal cardio- and neurodegenerative disorder that affects 1 in 50000 humans, is caused by decreased levels of the protein frataxin. Although frataxin is nuclear-encoded, it is targeted to the mitochondrial matrix and necessary for proper regulation of cellular iron homeostasis. Frataxin is required for the cellular production of both heme and iron-sulfur (Fe-S) clusters. Monomeric frataxin binds with high affinity to ferrochelatase, the enzyme involved in iron insertion into porphyrin during heme production. Monomeric frataxin also binds to Isu, the scaffold protein required for assembly of Fe-S cluster intermediates. These processes (heme and Fe-S cluster assembly) sharemore » requirements for iron, suggesting that monomeric frataxin might function as the common iron donor. To provide a molecular basis to better understand frataxin's function, we have characterized the binding properties and metal-site structure of ferrous iron bound to monomeric yeast frataxin. Yeast frataxin is stable as an iron-loaded monomer, and the protein can bind two ferrous iron atoms with micromolar binding affinity. Frataxin amino acids affected by the presence of iron are localized within conserved acidic patches located on the surfaces of both helix-1 and strand-1. Under anaerobic conditions, bound metal is stable in the high-spin ferrous state. The metal-ligand coordination geometry of both metal-binding sites is consistent with a six-coordinate iron-(oxygen/nitrogen) based ligand geometry, surely constructed in part from carboxylate and possibly imidazole side chains coming from residues within these conserved acidic patches on the protein. On the basis of our results, we have developed a model for how we believe yeast frataxin interacts with iron.« less

  12. Reductive precipitation of metals photosensitized by tin and antimony porphyrins

    DOEpatents

    Shelnutt, John A.; Gong, Weiliang; Abdelouas, Abdesselam; Lutze, Werner

    2003-09-30

    A method for reducing metals using a tin or antimony porphyrin by forming an aqueous solution of a tin or antimony porphyrin, an electron donor, such as ethylenediaminetetraaceticacid, triethylamine, triethanolamine, and sodium nitrite, and at least one metal compound selected from a uranium-containing compound, a mercury-containing compound, a copper-containing compound, a lead-containing compound, a gold-containing compound, a silver-containing compound, and a platinum-containing compound through irradiating the aqueous solution with light.

  13. Ytterbium-porphyrins as a new class of the luminescent labels

    NASA Astrophysics Data System (ADS)

    Tsvirko, M.; Korovin, Yu; Rusakova, N.

    2007-08-01

    New complexes of ytterbium with asymmetric porphyrins containing substituents in β-positions and hydrophobic meso-(monophenyl-p-oxypropyl)triphenylporphyrin (OPP) were obtained and characterized by elemental analysis, IR, UV-Vis absorption and luminescence spectroscopy. Electronic absorption, luminescence and luminescence excitation spectra of these complexes were studied at 295 K in DMF solutions and in the water-lecithin medium. The 4f-luminescence of ytterbium-porphyrins in the near infrared (IR) spectral region (λmax = 980 nm) is observed under excitation in Soret band (400-430 nm). The effect of substituent in porphyrin macroring on the 4f-luminescent properties was also investigated. The conjugates of these compounds with protein molecules - bovine serum albumin (BSA) were investigated as well. These compounds are interesting at the initial stage of diagnostics of tumor tissues as IR-luminescent probes due to their spectral-luminescent characteristics and some biochemical properties.

  14. The Important Role of Halogen Bond in Substrate Selectivity of Enzymatic Catalysis

    NASA Astrophysics Data System (ADS)

    Jiang, Shuiqin; Zhang, Lujia; Cui, Dongbin; Yao, Zhiqiang; Gao, Bei; Lin, Jinping; Wei, Dongzhi

    2016-10-01

    The use of halogen bond is widespread in drug discovery, design, and clinical trials, but is overlooked in drug biosynthesis. Here, the role of halogen bond in the nitrilase-catalyzed synthesis of ortho-, meta-, and para-chlorophenylacetic acid was investigated. Different distributions of halogen bond induced changes of substrate binding conformation and affected substrate selectivity. By engineering the halogen interaction, the substrate selectivity of the enzyme changed, with the implication that halogen bond plays an important role in biosynthesis and should be used as an efficient and reliable tool in enzymatic drug synthesis.

  15. Tropospheric impacts of volcanic halogen emissions: first simulations of reactive halogen chemistry in the Eyjafjallajökull eruption plume

    NASA Astrophysics Data System (ADS)

    Roberts, Tjarda

    2013-04-01

    Volcanic plumes are regions of high chemical reactivity. Instrumented research aircraft that probed the 2010 Icelandic Eyjafjallajökull eruption plume identified in-plume ozone depletion and reactive halogens (Cl, BrO), the latter also detected by satellite. These measurements add to growing evidence that volcanic plumes support rapid reactive halogen chemistry, with predicted impacts including depletion of atmospheric oxidants and mercury deposition. However, attempts to simulate volcanic plume halogen chemistry and predict impacts are subject to considerable uncertainties. e.g. in rate constants for HOBr reactive uptake (see this session: EGU2013-6076), or in the high-temperature initialisation. Model studies attempting to replicate volcanic plume halogen chemistry are restricted by a paucity of field data that is required both for model tuning and verification, hence reported model 'solutions' are not necessarily unique. To this end, the aircraft, ground-based and satellite studies of the Eyjafjallajökull eruption provide a valuable combination of datasets for improving our understanding of plume chemistry and impacts. Here, PlumeChem simulations of Eyjafjallajökull plume reactive halogen chemistry and impacts are presented and verified by observations for the first time. Observed ozone loss, a function of plume strength and age, is quantitatively reproduced by the model. Magnitudinal agreement to reported downwind BrO and Cl is also shown. The model predicts multi-day impacts, with reactive bromine mainly as BrO, HOBr and BrONO2 during daytime, and Br2 and BrCl at night. BrO/SO2 is reduced in more dispersed plumes due to enhanced partitioning to HOBr, of potential interest to satellite studies of BrO downwind of volcanoes. Additional predicted impacts of Eyjafjallajökull volcanic plume halogen chemistry include BrO-mediated depletion of HOx that reduces the rate of SO2 oxidation to H2SO4, hence the formation of sulphate aerosol. The model predicts NOx is

  16. Halogen bonding based recognition processes: a world parallel to hydrogen bonding.

    PubMed

    Metrangolo, Pierangelo; Neukirch, Hannes; Pilati, Tullio; Resnati, Giuseppe

    2005-05-01

    Halogen bonding is the noncovalent interaction between halogen atoms (Lewis acids) and neutral or anionic Lewis bases. The main features of the interaction are given, and the close similarity with the hydrogen bonding will become apparent. Some heuristic principles are presented to develop a rational crystal engineering based on halogen bonding. The focus is on halogen-bonded supramolecular architectures given by halocarbons. The potential of the interaction is shown by useful applications in the field of synthetic chemistry, material science, and bioorganic chemistry.

  17. Ratiometric Fluorescent Detection of Pb2+ by FRET-Based Phthalocyanine-Porphyrin Dyads.

    PubMed

    Zhang, Dongli; Zhu, Mengliang; Zhao, Luyang; Zhang, Jinghui; Wang, Kang; Qi, Dongdong; Zhou, Yang; Bian, Yongzhong; Jiang, Jianzhuang

    2017-12-04

    Sensitive and selective detection of Pb 2+ is a very worthwhile endeavor in terms of both human health and environmental protection, as the heavy metal is fairly ubiquitous and highly toxic. In this study, we designed phthalocyanine-porphyrin (Pc-Por) heterodyads, namely, H 2 Pc-α-ZnPor (1) and H 2 Pc-β-ZnPor (2), by connecting a zinc(II) porphyrin moiety to the nonperipheral (α) or peripheral (β) position of a metal-free phthalocyanine moiety. Upon excitation at the porphyrin Soret region (420 nm), both of the dyads exhibited not only a porphyrin emission (605 nm) but also a phthalocyanine emission (ca. 700 nm), indicating the occurrence of intramolecular fluorescence resonance energy transfer (FRET) processes from the porphyrin donor to the phthalocyanine acceptor. The dyads can selectively bind Pb 2+ in the phthalocyanine core leading to a red shift of the phthalocyanine absorption and thus a decrease of spectral overlap between the porphyrin emission and phthalocyanine absorption, which in turn suppresses the intramolecular FRET. In addition, the binding of Pb 2+ can highly quench the emission of phthalocyanine by heavy-metal ion effects. The synergistic coupled functions endow the dyads with remarkable ratiometric fluorescent responses at two distinct wavelengths (F 605 /F 703 for 1 and F 605 /F 700 for 2). The emission intensity ratio increased as a linear function to the concentration of Pb 2+ in the range of 0-4.0 μM, whereas the detection limits were determined to be 3.4 × 10 -9 and 2.2 × 10 -8 M for 1 and 2, respectively. Furthermore, by comparative study of 1 and 2, the effects of distance and relative orientation between Pc and ZnPor fluorophores on the FRET efficiency and sensing performance were highlighted, which is helpful for further optimizing such FRET systems.

  18. Morphology-Controlled Synthesis and Metalation of Porphyrin Nanoparticles with Enhanced Photocatalytic Performance

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Jiefei; Zhong, Yong; Wang, Liang

    The design and engineering of the size, shape, and chemistry of photoactive building blocks enables the fabrication of functional nanoparticles for applications in light harvesting, photocatalytic synthesis, water splitting, phototherapy, and photodegradation. Here, we report the synthesis of such nanoparticles through a surfactant-assisted interfacial self-assembly process using optically active porphyrin as a functional building block. The self-assembly process relies on specific interactions such as π–π stacking and metalation (metal atoms and ligand coordination) between individual porphyrin building blocks. Depending on the kinetic conditions and type of surfactants, resulting structures exhibit well-defined one- to three-dimensional morphologies such as nanowires, nanooctahedra, andmore » hierarchically ordered internal architectures. Specifically, electron microscopy and X-ray diffraction results indicate that these nanoparticles exhibit stable single-crystalline and nanoporous frameworks. In conclusion, due to the hierarchical ordering of the porphyrins, the nanoparticles exhibit collective optical properties resulted from coupling of molecular porphyrins and photocatalytic activities such as photodegradation of methyl orange (MO) pollutants and hydrogen production.« less

  19. Morphology-Controlled Synthesis and Metalation of Porphyrin Nanoparticles with Enhanced Photocatalytic Performance

    DOE PAGES

    Wang, Jiefei; Zhong, Yong; Wang, Liang; ...

    2016-09-12

    The design and engineering of the size, shape, and chemistry of photoactive building blocks enables the fabrication of functional nanoparticles for applications in light harvesting, photocatalytic synthesis, water splitting, phototherapy, and photodegradation. Here, we report the synthesis of such nanoparticles through a surfactant-assisted interfacial self-assembly process using optically active porphyrin as a functional building block. The self-assembly process relies on specific interactions such as π–π stacking and metalation (metal atoms and ligand coordination) between individual porphyrin building blocks. Depending on the kinetic conditions and type of surfactants, resulting structures exhibit well-defined one- to three-dimensional morphologies such as nanowires, nanooctahedra, andmore » hierarchically ordered internal architectures. Specifically, electron microscopy and X-ray diffraction results indicate that these nanoparticles exhibit stable single-crystalline and nanoporous frameworks. In conclusion, due to the hierarchical ordering of the porphyrins, the nanoparticles exhibit collective optical properties resulted from coupling of molecular porphyrins and photocatalytic activities such as photodegradation of methyl orange (MO) pollutants and hydrogen production.« less

  20. Degradation of halogenated aliphatic compounds by Xanthobacter autotrophicus GJ10.

    PubMed Central

    Janssen, D B; Scheper, A; Dijkhuizen, L; Witholt, B

    1985-01-01

    A bacterium that is able to utilize a number of halogenated short-chain hydrocarbons and halogenated carboxylic acids as sole carbon source for growth was identified as a strain of Xanthobacter autotrophicus. The organism constitutively produces two different dehalogenases. One enzyme is specific for halogenated alkanes, whereas the other, which is more heat stable and has a higher pH optimum, is specific for halogenated carboxylic acids. Haloalkanes were hydrolyzed in cell extracts to produce alcohols and halide ions, and a route for the metabolism of 1,2-dichlorethane is proposed. Both dehalogenases show a broad substrate specificity, allowing the degradation of bromine- and chlorine-substituted organic compounds. The results show that X. autotrophicus may play a role in the degradation of organochlorine compounds and that hydrolytic dehalogenases may be involved in the microbial metabolism of short-chain halogenated hydrocarbons in microorganisms. Images PMID:3994371

  1. Electroreduction of Halogenated Organic Compounds

    NASA Astrophysics Data System (ADS)

    Rondinini, Sandra; Vertova, Alberto

    The electroreductive cleavage of the carbon-halogen bond in halogenated organic compounds has been extensively studied for more than 70 years, since it is prodromal to a large variety of synthetic applications in organic electrochemistry. Over the years the research interest have progressively included the environmental applications, since several organic halocompounds are known to have (or have had) a serious environmental impact because of their (present or past) wide use as cleaning agents, herbicides, cryogenic fluids, reagents (e.g. allyl and vinyl monomers) for large production materials, etc. Recent studies have also demonstrated the wide spread out- and in-door-presence of volatile organic halides, although at low level, in connexion with residential and non-residential (e.g. stores, restaurants and transportation) activities. In this context, the detoxification of emissions to air, water and land by the selective removal of the halogen group represents a valid treatment route, which, although not leading to the complete mineralization of the pollutants, produces less harmful streams to be easily treated by electrochemical or conventional techniques. The electroreduction process is analysed and discussed in terms of electrode material, reaction medium, cell design and operation, and of substrate classification.

  2. Structures and electronic states of halogen-terminated graphene nano-flakes

    NASA Astrophysics Data System (ADS)

    Tachikawa, Hiroto; Iyama, Tetsuji

    2015-12-01

    Halogen-functionalized graphenes are utilized as electronic devices and energy materials. In the present paper, the effects of halogen-termination of graphene edge on the structures and electronic states of graphene flakes have been investigated by means of density functional theory (DFT) method. It was found that the ionization potential (Ip) and electron affinity of graphene (EA) are blue-shifted by the halogen termination, while the excitation energy is red-shifted. The drastic change showed a possibility as electronic devices such as field-effect transistors. The change of electronic states caused by the halogen termination of graphene edge was discussed on the basis of the theoretical results.

  3. Halogen Substitution Effects on N2 O Schiff Base Ligands in Unprecedented Abrupt FeII Spin Crossover Complexes.

    PubMed

    Phonsri, Wasinee; Macedo, David S; Vignesh, Kuduva R; Rajaraman, Gopalan; Davies, Casey G; Jameson, Guy N L; Moubaraki, Boujemaa; Ward, Jas S; Kruger, Paul E; Chastanet, Guillaume; Murray, Keith S

    2017-05-23

    A family of halogen-substituted Schiff base iron(II) complexes, [Fe II (qsal-X) 2 ], (qsal-X=5-X-N-(8-quinolyl)salicylaldimines)) in which X=F (1), Cl (2), Br (3) or I (4) has been investigated in detail. Compound 1 shows a temperature invariant high spin state, whereas the others all show abrupt spin transitions, at or above room temperature, namely, 295 K (X=I) up to 342 K (X=Br), these being some of the highest T 1/2 values obtained, to date, for Fe II N/O species. We have recently reported subtle symmetry breaking in [Fe II (qsal-Cl) 2 ] 2 with two spin transition steps occurring at 308 and 316 K. A photomagnetic study reveals almost full HS conversion of [Fe II (qsal-I) 2 ] 4 at low temperature (T(LIESST)=54 °K). The halogen substitution effects on the magnetic properties, as well as the crystal packing of the [Fe II (qsal-X) 2 ] compounds and theoretical calculations, are discussed in depth, giving important knowledge for the design of new spin crossover materials. In comparison to the well known iron(III) analogues, [Fe III (qsal-X) 2 ] + , the two extra π-π and P4AE interactions found in [Fe II (qsal-X) 2 ] compounds, are believed to be accountable for the spin transitions occurring at ambient temperatures. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Catalytic and inhibiting effect of amino acids on the porphyrin metallation reactions

    NASA Astrophysics Data System (ADS)

    Mamardashvili, Galina M.; Zhdanova, Daria Yu.; Mamardashvili, Nugzar Zh.; Koifman, Oskar I.; Dehaen, Wim

    In the present work, using the interaction of tetra-(4-sulfophenyl)porphyrin with copper(II) chloride as an example, it has been shown how different amino acid additives (glycine, valine, leucine and tryptophan) catalyze or inhibit the formation of Cu-porphyrin as a function of the chemical environment (borate buffer (pH7.4), DMSO) and the concentration of the additive. It has been demonstrated that the type of amino acid affects the complexation reaction rate. Possible mechanisms of metalloporphyrin formation and the ways of their acceleration are discussed. Ways in which different amino acid additives catalyze or inhibit the interaction of tetra-(4-sulfophenyl)porphyrin with copper(II) chloride are examined.

  5. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jarvis, Jacqueline M.; Sudasinghe, Nilusha M.; Albrecht, Karl O.

    We apply Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for direct characterization of iron-porphyrins in hydrothermal liquefaction (HTL) biocrude oils derived from two algae: Tetraselmis sp. and cyanobacteria. The ironporphyrin compounds are shown to cause catalyst bed plugging during hydroprocessing due to iron deposition. Inductively-coupled plasma optical emission spectrometry (ICPOES) was utilized for iron quantitation in the plugged catalyst beds formed through hydroprocessing of the two HTL biocrudes and identifies an enrichment of iron in the upper five centimeters of the catalyst bed for Tetraselmis sp. (Fe=100,728 ppm) and cyanobacteria (Fe=115,450 ppm). Direct infusion FT-ICR MS analysis ofmore » the two HTL biocrudes with optimized instrument conditions facilitates rapid screening and identification of iron-porphyrins without prior chromatographic separation. With FT-ICR MS we identify 138 unique iron-porphyrin compounds in the two HTL biocrudes that are structurally similar to metal-porphyrins (e.g. Ni and V) observed in petroleum. No ironporphyrins are observed in the cyanobacteria HTL biocrude after hydroprocessing, which indicates that iron-porphyrin structures in the HTL biocrude are degraded during hydroprocessing. Hydrodemetallization reactions that occur through hydroprocessing of HTL biocrudes could be responsible for the decomposition of iron-porphyrin structures leading to metal deposition in the catalyst bed that result in catalyst deactivation and bed plugging, and must be addressed for effective upgrading of algal HTL biocrudes.« less

  6. 40 CFR 721.5452 - Alkali metal salt of halogenated organoborate (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkali metal salt of halogenated... Specific Chemical Substances § 721.5452 Alkali metal salt of halogenated organoborate (generic). (a... generically as alkali metal salt of halogenated organoborate (PMN P-00-0638) is subject to reporting under...

  7. 40 CFR 721.5452 - Alkali metal salt of halogenated organoborate (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkali metal salt of halogenated... Specific Chemical Substances § 721.5452 Alkali metal salt of halogenated organoborate (generic). (a... generically as alkali metal salt of halogenated organoborate (PMN P-00-0638) is subject to reporting under...

  8. Photosensitized Protein-Damaging Activity, Cytotoxicity, and Antitumor Effects of P(V)porphyrins Using Long-Wavelength Visible Light through Electron Transfer.

    PubMed

    Hirakawa, Kazutaka; Ouyang, Dongyan; Ibuki, Yuko; Hirohara, Shiho; Okazaki, Shigetoshi; Kono, Eiji; Kanayama, Naohiro; Nakazaki, Jotaro; Segawa, Hiroshi

    2018-05-21

    Photodynamic therapy (PDT) is a less-invasive treatment for cancer through the administration of less-toxic porphyrins and visible-light irradiation. Photosensitized damage of biomacromolecules through singlet oxygen ( 1 O 2 ) generation induces cancer cell death. However, a large quantity of porphyrin photosensitizer is required, and the treatment effect is restricted under a hypoxic cellular condition. Here we report the phototoxic activity of P(V)porphyrins: dichloroP(V)tetrakis(4-methoxyphenyl)porphyrin (CLP(V)TMPP), dimethoxyP(V)tetrakis(4-methoxyphenyl)porphyrin (MEP(V)TMPP), and diethyleneglycoxyP(V)tetrakis(4-methoxyphenyl)porphyrin (EGP(V)TMPP). These P(V)porphyrins damaged the tryptophan residue of human serum albumin (HSA) under the irradiation of long-wavelength visible light (>630 nm). This protein photodamage was barely inhibited by sodium azide, a quencher of 1 O 2 . Fluorescence lifetimes of P(V)porphyrins with or without HSA and their redox potentials supported the electron-transfer-mediated oxidation of protein. The photocytotoxicity of these P(V)porphyrins to HeLa cells was also demonstrated. CLP(V)TMPP did not exhibit photocytotoxicity to HaCaT, a cultured human skin cell, and MEP(V)TMPP and EGP(V)TMPP did; however, cellular DNA damage was barely observed. In addition, a significant PDT effect of these P(V) porphyrins on a mouse tumor model comparable with the traditional photosensitizer was also demonstrated. These findings suggest the cancer selectivity of these P(V)porphyrins and lower carcinogenic risk to normal cells. Electron-transfer-mediated oxidation of biomacromolecules by P(V)porphyrins using long-wavelength visible light should be advantageous for PDT of hypoxic tumor.

  9. Metallic nanoshells on porphyrin-stabilized emulsions

    DOEpatents

    Wang, Haorong; Song, Yujiang; Shelnutt, John A; Medforth, Craig J

    2013-10-29

    Metal nanostructures formed by photocatalytic interfacial synthesis using a porphyrin-stabilized emulsion template and the method for making the nanostructures. Catalyst-seeded emulsion droplets are employed as templates for hollow-nanoshell growth. The hollow metal nanospheres may be formed with or without inclusions of other materials.

  10. Stabilization and Structure of the cis  Tautomer of a Free-Base Porphyrin

    DOE PAGES

    Thomas, Kolle E.; McCormick, Laura J.; Vazquez-Lima, Hugo; ...

    2017-03-29

    Single-crystal X-ray analysis of the β-heptakis(trifluoromethyl)-meso-tetrakis(p-fluorophenyl)porphyrin, H 2[(CF 3) 7T pFPP], has revealed the first example of a stable cis tautomer of a free-base porphyrin, the long-postulated intermediate of porphyrin tautomerism. The stability of the unique molecule appears to reflect a dual origin: a strongly saddled porphyrin skeleton, which alleviates electrostatic repulsion between the two NH protons, and two polarization-enhanced, transannular N−H⋅⋅⋅O−H⋅⋅⋅N hydrogen bond chains, each involving a molecule of water. DFT calculations suggest that the observed tautomer has a lower energy than the alternative, doubly hydrated trans tautomer by some 8.3 kcal mol −1 . A fascinating prospect thusmore » exists that H 2[(CF 3) 7T pFPP]⋅ 2H 2O and cognate structures may act as supramolecular synthons, which, given their chirality, may even be amenable to resolution into optically pure enantiomers.« less

  11. Red electroluminescence and photoluminescence properties of new porphyrin compounds

    NASA Astrophysics Data System (ADS)

    Zhang, X. H.; Xie, Z. Y.; Wu, F. P.; Zhou, L. L.; Wong, O. Y.; Lee, C. S.; Kwong, H. L.; Lee, S. T.; Wu, S. K.

    2003-12-01

    Three new porphyrin compounds with saturated red emission were synthesized and their photoluminescence and electroluminescence were studied. The emission of the new dopants peaked at about 635-655 nm and the half-width of the emission peaks was very narrow (below 30 nm). Of the three porphyrin compounds, the one (TBDPP) with the smallest conjugation system had the highest fluorescent quantum yield of 21% in solution. Organic light-emitting diodes using TBDPP as a dopant showed saturated red emission (CIE coordinates of x=0.69, y=0.29) with a luminance of 150 cd/m 2 at a driving voltage of 22 V.

  12. Palladium-catalyzed Kumada coupling reaction of bromoporphyrins with silylmethyl Grignard reagents: preparation of silylmethyl-substituted porphyrins as a multipurpose synthon for fabrication of porphyrin systems.

    PubMed

    Sugita, Noriaki; Hayashi, Satoshi; Hino, Fumio; Takanami, Toshikatsu

    2012-12-07

    We have developed an efficient method for preparing silylmethyl-substituted porphyrins via the palladium-catalyzed Kumada cross-coupling reaction of bromoporphyrins with silylmethyl Grignard reagents. We demonstrated the synthetic utility of these silylmethylporphyrins as a multipurpose synthon for fabricating porphyrin derivatives through a variety of transformations of the silylmethyl groups, including the DDQ-promoted oxidative conversion to CHO, CH(2)OH, CH(2)OMe, and CH(2)F functionalities and the fluoride ion-mediated desilylative introduction of carbon-carbon single and double bonds.

  13. Noncovalent functionalization of carbon nanotubes with porphyrins: meso-tetraphenylporphine and its transition metal complexes.

    PubMed

    Basiuk, Elena V; Basiuk, Vladimir A; Santiago, Patricia; Puente-Lee, Iván

    2007-01-01

    Noncovalent functionalization of carbon nanotubes with meso-tetraphenylporphine (H2TPP) and its metal(II) complexes NiTPP and CoTPP was studied by means of different experimental techniques and theoretical calculations. As follows from the experimental adsorption curves, free H2TPP ligand exhibits the strongest adsorption of three porphyrins tested, followed by CoTPP and NiTPP. At the highest porphyrin concentrations studied, the adsorption at multi-walled carbon nanotubes was about 2% (by weight) for H2TPP, 1% for CoTPP, and 0.5% for NiTPP. Transmission electron microscopy observations revealed carbon nanotubes with a variable degree of surface coverage with porphyrin molecules. According to scanning electron microscopy, the nanotubes glue together rather than debundle; apparently, a large porphyrin excess resulting in polymolecular adsorption is essential for exfoliation/debundling of the nanotube ropes. The nanotube/porphyrins hybrids were studied by infrared and Raman spectroscopy, as well as by scanning tunneling microscopy. Electronic structure calculations were performed at the B3LYP/LANL2MB theoretical level with the unsubstituted porphine (H2P) and its Co(II) complex, on one hand, and open-end armchair (5,5) (ANT) and zigzag (8,0) (ZNT) SWNT models, on the other hand. The interaction of H2P with ANT was found to be by 3.9 kcal mol(-1) stronger than that of CoP. At the same time, CoP+ZNT complex is more stable by 42.7 kcal mol(-1) as compared to H2P+ZNT According to these calculated results, the free porphyrins interact less selectively with zigzag and armchair (i.e., semiconducting and metallic) nanotubes, whereas the difference becomes very large for the metal porphyrins. HOMO-LUMO structure, electrostatic potential and spin density distribution for the paramagnetic cobalt(II) complexes were analyzed.

  14. Ultrafast Photoinduced Electron Transfer in a π-Conjugated Oligomer/Porphyrin Complex.

    PubMed

    Aly, Shawkat M; Goswami, Subhadip; Alsulami, Qana A; Schanze, Kirk S; Mohammed, Omar F

    2014-10-02

    Controlling charge transfer (CT), charge separation (CS), and charge recombination (CR) at the donor-acceptor interface is extremely important to optimize the conversion efficiency in solar cell devices. In general, ultrafast CT and slow CR are desirable for optimal device performance. In this Letter, the ultrafast excited-state CT between platinum oligomer (DPP-Pt(acac)) as a new electron donor and porphyrin as an electron acceptor is monitored for the first time using femtosecond (fs) transient absorption (TA) spectroscopy with broad-band capability and 120 fs temporal resolution. Turning the CT on/off has been shown to be possible either by switching from an organometallic oligomer to a metal-free oligomer or by controlling the charge density on the nitrogen atom of the porphyrin meso unit. Our time-resolved data show that the CT and CS between DPP-Pt(acac) and cationic porphyrin are ultrafast (approximately 1.5 ps), and the CR is slow (ns time scale), as inferred from the formation and the decay of the cationic and anionic species. We also found that the metallic center in the DPP-Pt(acac) oligomer and the positive charge on the porphyrin are the keys to switching on/off the ultrafast CT process.

  15. Comparison of Carbon XANES Spectra from an Iron Sulfide from Comet Wild 2 with an Iron Sulfide Interplanetary Dust Particle

    NASA Technical Reports Server (NTRS)

    Wirick, S.; Flynn, G. J.; Keller, L. P.; Sanford, S. A.; Zolensky, M. E.; Messenger, Nakamura K.; Jacobsen, C.

    2008-01-01

    Among one of the first particles removed from the aerogel collector from the Stardust sample return mission was an approx. 5 micron sized iron sulfide. The majority of the spectra from 5 different sections of this particle suggests the presence of aliphatic compounds. Due to the heat of capture in the aerogel we initially assumed these aliphatic compounds were not cometary but after comparing these results to a heated iron sulfide interplanetary dust particle (IDP) we believe our initial interpretation of these spectra was not correct. It has been suggested that ice coating on iron sulfides leads to aqueous alteration in IDP clusters which can then lead to the formation of complex organic compounds from unprocessed organics in the IDPs similar to unprocessed organics found in comets [1]. Iron sulfides have been demonstrated to not only transform halogenated aliphatic hydrocarbons but also enhance the bonding of rubber to steel [2,3]. Bromfield and Coville (1997) demonstrated using Xray photoelectron spectroscopy that "the surface enhancement of segregated sulfur to the surface of sulfided precipitated iron catalysts facilitates the formation of a low-dimensional structure of extraordinary properties" [4]. It may be that the iron sulfide acts in some way to protect aliphatic compounds from alteration due to heat.

  16. Water-splitting using photocatalytic porphyrin-nanotube composite devices

    DOEpatents

    Shelnutt, John A [Tijeras, NM; Miller, James E [Albuquerque, NM; Wang, Zhongchun [Albuquerque, NM; Medforth, Craig J [Winters, CA

    2008-03-04

    A method for generating hydrogen by photocatalytic decomposition of water using porphyrin nanotube composites. In some embodiments, both hydrogen and oxygen are generated by photocatalytic decomposition of water.

  17. Metal halogen battery system with multiple outlet nozzle for hydrate

    DOEpatents

    Bjorkman, Jr., Harry K.

    1983-06-21

    A metal halogen battery system, including at least one cell having a positive electrode and a negative electrode contacted by aqueous electrolyte containing the material of said metal and halogen, store means whereby halogen hydrate is formed and stored as part of an aqueous material, means for circulating electrolyte through the cell and to the store means, and conduit means for transmitting halogen gas formed in the cell to a hydrate former whereby the hydrate is formed in association with the store means, said store means being constructed in the form of a container which includes a filter means, said filter means being inoperative to separate the hydrate formed from the electrolyte, said system having, a hydrate former pump means associated with the store means and being operative to intermix halogen gas with aqueous electrolyte to form halogen hydrate, said hydrate former means including, multiple outlet nozzle means connected with the outlet side of said pump means and being operative to minimize plugging, said nozzle means being comprised of at least one divider means which is generally perpendicular to the rotational axes of gears within the pump means, said divider means acting to divide the flow from the pump means into multiple outlet flow paths.

  18. Investigation of iron(III) complex with crown-porphyrin

    NASA Astrophysics Data System (ADS)

    Pankratov, Denis A.; Dolzhenko, Vladimir D.; Stukan, Reonald A.; Al Ansari, Yana F.; Savinkina, Elena V.; Kiselev, Yury M.

    2013-08-01

    Iron complex of 5-(4-(((4'-hydroxy-benzo-15-crown-5)-5'-yl)diazo)phenyl)-10,15,20-triphenylporphyrin was investigated by 57Fe Mössbauer spectroscopy and EPR. Two Fe sites were identified; they give two differing signals, doublet and wide absorption in a large velocity interval. EPR spectra of solutions of the complex in chloroform at room temperature also show two signals with g = 2.064, AFe = 0.032 cm - 1; g = 2.015, AFe = 0.0034 cm - 1. The doublet asymmetry is studied vs. temperature and normal angle to the sample plane and gamma-beam. The isomer shift δ in the doublet varies from 0.25 to 0.41 mm/s in the 360-5 K temperature range, whereas quadruple splitting value is constant, Δ ˜ 0.65 mm/s. The relax absorption may be described as a wide singlet ( δ = 0.30- 0.44 mm/s and Γ = 2.83-3.38 mm/s); its relative area strongly depends on temperature. According to δ, both signals are assigned to Fe(III).

  19. New porphyrins bearing positively charged peripheral groups linked by a sulfonamide group to meso-tetraphenylporphyrin: interactions with calf thymus DNA.

    PubMed

    Manono, Janet; Marzilli, Patricia A; Marzilli, Luigi G

    2009-07-06

    New water-soluble cationic meso-tetraarylporphyrins (TArP, Ar = 4-C(6)H(4)) and some metal derivatives have been synthesized and characterized. One main goal was to assess if N-methylpyridinium (N-Mepy) groups must be directly attached to the porphyrin core for intercalative binding of porphyrins to DNA. The new porphyrins have the general formula, [T(R(2)R(1)NSO(2)Ar)P]X(4/8) (R(1) = CH(3) or H and R(2) = N-Mepy-n-CH(2) with n = 2, 3, or 4; or R(1) = R(2) = Et(3)NCH(2)CH(2)). Interactions of selected porphyrins and metalloporphyrins (Cu(II), Zn(II)) with calf thymus DNA were investigated by visible circular dichroism (CD), absorption, and fluorescence spectroscopies. The DNA-induced changes in the porphyrin Soret region (a positive induced CD feature and, at high DNA concentration, increases in the Soret band and fluorescence intensities) indicate that the new porphyrins interact with DNA in an outside, non-self-stacking binding mode. Several new metalloporphyrins did not increase DNA solution viscosity and thus do not intercalate, confirming the conclusion drawn from spectroscopic studies. Porphyrins known to intercalate typically bear two or more N-Mepy groups directly attached to the porphyrin ring, such as the prototypical meso-tetra(N-Mepy)porphyrin tetracation (TMpyP(4)). The distances between the nitrogens of the N-Mepy group are estimated to be approximately 11 A (cis) and 16 A (trans) for the relatively rigid TMpyP(4). For the new flexible porphyrin, [T(N-Mepy-4-CH(2)(CH(3))NSO(2)Ar)P]Cl(4), the distances between the nitrogens are estimated to be able to span the range from approximately 9 to approximately 25 A. Thus, the N-Mepy groups in the new porphyrins can adopt the same spacing as in known intercalators such as TMpyP(4). The absence of intercalation by the new porphyrins indicates that the propensity for the N-Mepy group to facilitate DNA intercalation of cationic porphyrins requires direct attachment of N-Mepy groups to the porphyrin core.

  20. Biodegradation of Trihalomethanes and Other Halogenated Aliphatic Compounds

    NASA Technical Reports Server (NTRS)

    Smith, G. B.

    1996-01-01

    The biological dehalogenation of common water pollutants such as trichloromethane (chloroform) and other halogenated aliphatic compounds was the subject of this project. Samples from diverse water environments such as from groundwater contaminated with halogenated compounds and wastewaters from regional treatment plants were studied to identify conditions that favor certain dehalogenation reactions over others. Gene probe analyses of DNA extracted from the dichlormethane-degrading wastewater indicated the presence of the gene coding for dichloromethane dehalogenase, indicating the genetic basis for the dechlorination activity observed. These studies indicate that methanogenic bacteria are the organisms responsible for the chloroform dechlorination. Dechlorination of a common chlorofluorocarbon (CFC-11) was identified in samples taken from a regional aquifer contaminated with halogenated aliphatic compounds.

  1. Porphyrins for boron neutron capture therapy

    DOEpatents

    Miura, Michiko; Gabel, Detlef

    1990-01-01

    Novel compounds for treatment of brain tumors in Boron Neutron Capture Therapy are disclosed. A method for preparing the compounds as well as pharmaceutical compositions containing said compounds are also disclosed. The compounds are water soluble, non-toxic and non-labile boronated porphyrins which show significant uptake and retention in tumors.

  2. Comparative study of binding interactions between porphyrin systems and aromatic compounds of biological importance by multiple spectroscopic techniques: A review

    NASA Astrophysics Data System (ADS)

    Makarska-Bialokoz, Magdalena

    2018-07-01

    The specific spectroscopic and redox properties of porphyrins predestine them to fulfill the role of sensors during interacting with different biologically active substances. Monitoring of binding interactions in the systems porphyrin-biologically active compound is a key question not only in the field of physiological functions of living organisms, but also in environmental protection, notably in the light of the rapidly growing drug consumption and concurrently the production of drug effluents. Not always beneficial action of drugs on natural porphyrin systems induces to further studies, with commercially available porphyrins as the model systems. Therefore the binding process between several water-soluble porphyrins and a series of biologically active compounds (e.g. caffeine, guanine, theophylline, theobromine, xanthine, uric acid) has been studied in different aqueous solutions analyzing their absorption and steady-state fluorescence spectra, the porphyrin fluorescence lifetimes and their quantum yields. The magnitude of the binding and fluorescence quenching constants values for particular quenchers decreases in a series: uric acid > guanine > caffeine > theophylline > theobromine > xanthine. In all the systems studied there are characters of static quenching, as a consequence of the π-π-stacked non-covalent and non-fluorescent complexes formation between porphyrins and interacting compounds, accompanied simultaneously by the additional specific binding interactions. The porphyrin fluorescence quenching can be explain by the photoinduced intermolecular electron transfer from aromatic compound to the center of the porphyrin molecule, playing the role of the binding site. Presented results can be valuable for designing of new fluorescent porphyrin chemosensors or monitoring of drug traces in aqueous solutions. The obtained outcomes have also the toxicological and medical importance, providing insight into the interactions of the water-soluble porphyrins with

  3. Assembly of Multi-Phthalocyanines on a Porphyrin Template by Fourfold Rotaxane Formation.

    PubMed

    Yamada, Yasuyuki; Kato, Tatsuhisa; Tanaka, Kentaro

    2016-08-22

    A stacked assembly composed of a porphyrin and two phthalocyanines was prepared through fourfold rotaxane formation. Two phthalocyanine molecules, bearing four 24-crown-8 units, were assembled onto a porphyrin template incorporating four sidechains with two dialkylammonium ions each through pseudorotaxane formation between crown ether units and ammonium ions. The Staudinger phosphite reaction, as the stoppering reaction, resulted in the formation of the stacked heterotrimer composed of a porphyrin and two phthalocyanines connected through a fourfold rotaxane structure. UV/Vis spectroscopic and electrochemical studies of the heterotrimer indicated that there is a significant electronic interaction between the two phthalocyanine units due to the close stacking. The electrochemical oxidation process of the stacked heterotrimer was studied by cyclic voltammetry and spectroelectrochemistry. Electron paramagnetic resonance (EPR) spectroscopy of a dinuclear Cu(II) complex, in which two Cu(II) phthalocyanines were assembled on a metal-free porphyrin template, revealed that two Cu(II) phthalocyanines were located within the stacking distance, which resulted in an antiferromagnetic interaction between the two S=1/2 spins in the ground state of the Cu(2+) ions in the heterotrimer. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Solvent effects on the fluorescence and effective three-photon absorption of a Zn(II)-[meso-tetrakis(4-octyloxyphenyl)porphyrin

    NASA Astrophysics Data System (ADS)

    Wan, Yong; Xue, Yuxiong; Sheng, Ning; Rui, Guanghao; Lv, Changgui; He, Jun; Gu, Bing; Cui, Yiping

    2018-06-01

    The fluorescence and effective three-photon absorption (3PA) properties of Zn(II)-[meso-tetrakis(4-octyloxyphenyl)porphyrin] (labeled Zn(II)-porphyrin) dissolved in three different polar solvents were systematically investigated. The electrochemical and photophysical properties of Zn(II)-porphyrin were investigated by 1H NMR spectra, IR spectra, mass spectroscopy, and electronic absorption spectra. The fluorescence emission of Zn(II)-porphyrin in three different solvents excited at the wavelengths of 420 nm (Soret band) and 550 nm (Q-band) were analyzed. By performing Z-scan experiments with femtosecond laser pulses at a wavelength of 800 nm, the effective 3PA process of Zn(II)-porphyrin in three different solvents was observed and the underlying mechanism was discussed in detail. It is found that the fluorescence spectra slightly depend on the polarity of the solvent. Interestingly, the effective 3PA properties of Zn(II)-porphyrin strongly depend on the solvent polarity. The lower the solvent polarity is, the larger effective 3PA cross-section is. Low polar solvents are beneficial to applications of Zn(II)-porphyrin in optical limiting, photodynamic therapy, etc.

  5. The unique role of halogen substituents in the design of modern agrochemicals.

    PubMed

    Jeschke, Peter

    2010-01-01

    The past 30 years have witnessed a period of significant expansion in the use of halogenated compounds in the field of agrochemical research and development. The introduction of halogens into active ingredients has become an important concept in the quest for a modern agrochemical with optimal efficacy, environmental safety, user friendliness and economic viability. Outstanding progress has been made, especially in synthetic methods for particular halogen-substituted key intermediates that were previously prohibitively expensive. Interestingly, there has been a rise in the number of commercial products containing 'mixed' halogens, e.g. one or more fluorine, chlorine, bromine or iodine atoms in addition to one or more further halogen atoms. Extrapolation of the current trend indicates that a definite growth is to be expected in fluorine-substituted agrochemicals throughout the twenty-first century. A number of these recently developed agrochemical candidates containing halogen substituents represent novel classes of chemical compounds with new modes of action. However, the complex structure-activity relationships associated with biologically active molecules mean that the introduction of halogens can lead to either an increase or a decrease in the efficacy of a compound, depending on its changed mode of action, physicochemical properties, target interaction or metabolic susceptibility and transformation. In spite of modern design concepts, it is still difficult to predict the sites in a molecule at which halogen substitution will result in optimal desired effects. This review describes comprehensively the successful utilisation of halogens and their unique role in the design of modern agrochemicals, exemplified by various commercial products from Bayer CropScience coming from different agrochemical areas.

  6. Optical Gas Sensing of Ammonia and Amines Based on Protonated Porphyrin/TiO2 Composite Thin Films

    PubMed Central

    Castillero, Pedro; Roales, Javier; Lopes-Costa, Tânia; Sánchez-Valencia, Juan R.; Barranco, Angel; González-Elipe, Agustín R.; Pedrosa, José M.

    2016-01-01

    Open porous and transparent microcolumnar structures of TiO2 prepared by physical vapour deposition in glancing angle configuration (GLAD-PVD) have been used as host matrices for two different fluorescent cationic porphyrins, 5-(N-methyl 4-pyridyl)-10,15,20-triphenyl porphine chloride (MMPyP) and meso-tetra (N-methyl 4-pyridyl) porphine tetrachloride (TMPyP). The porphyrins have been anchored by electrostatic interactions to the microcolumns by self-assembly through the dip-coating method. These porphyrin/TiO2 composites have been used as gas sensors for ammonia and amines through previous protonation of the porphyrin with HCl followed by subsequent exposure to the basic analyte. UV–vis absorption, emission, and time-resolved spectroscopies have been used to confirm the protonation–deprotonation of the two porphyrins and to follow their spectral changes in the presence of the analytes. The monocationic porphyrin has been found to be more sensible (up to 10 times) than its tetracationic counterpart. This result has been attributed to the different anchoring arrangements of the two porphyrins to the TiO2 surface and their different states of aggregation within the film. Finally, there was an observed decrease of the emission fluorescence intensity in consecutive cycles of exposure and recovery due to the formation of ammonium chloride inside the film. PMID:28025570

  7. Likelihood of atom-atom contacts in crystal structures of halogenated organic compounds.

    PubMed

    Jelsch, Christian; Soudani, Sarra; Ben Nasr, Cherif

    2015-05-01

    The likelihood of occurrence of intermolecular contacts in crystals of halogenated organic compounds has been analysed statistically using tools based on the Hirshfeld surface. Several families of small halogenated molecules (containing organic F, Cl, Br or I atoms) were analysed, based on chemical composition and aromatic or aliphatic character. The behaviour of crystal contacts was also probed for molecules containing O or N. So-called halogen bonding (a halogen making short interactions with O or N, or a π interaction with C) is generally disfavoured, except when H is scarce on the molecular surface. Similarly, halogen⋯halogen contacts are more rare than expected, except for molecules that are poor in H. In general, the H atom is found to be the preferred partner of organic halogen atoms in crystal structures. On the other hand, C⋯C interactions in parallel π-stacking have a high propensity to occur in halogenated aromatic molecules. The behaviour of the four different halogen species (F, Cl, Br, I) is compared in several chemical composition contexts. The analysis tool can be refined by distinguishing several types for a given chemical species, such as H atoms bound to O or C. Such distinction shows, for instance, that C-H⋯Cl and O-H⋯O are the preferred interactions in compounds containing both O and Cl.

  8. Cutaneous porphyrins exhibit anti-stokes fluorescence that is detectable in sebum (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Tian, Giselle; Zeng, Haishan; Zhao, Jianhua; Wu, Zhenguo; Al Jasser, Mohammed; Lui, Harvey; Mclean, David I.

    2016-02-01

    Porphyrins produced by Propionibacterium acnes represent the principal fluorophore associated with acne, and appear as orange-red luminescence under the Wood's lamp. Assessment of acne based on Wood's lamp (UV) or visible light illumination is limited by photon penetration depth and has limited sensitivity for earlier stage lesions. Inducing fluorescence with near infrared (NIR) excitation may provide an alternative way to assess porphyrin-related skin disorders. We discovered that under 785 nm CW laser excitation PpIX powder exhibits fluorescence emission in the shorter wavelength range of 600-715 nm with an intensity that is linearly dependent on the excitation power. We attribute this shorter wavelength emission to anti-Stokes fluorescence. Similar anti-Stokes fluorescence was also detected focally in all skin-derived samples containing porphyrins. Regular (Stokes) fluorescence was present under UV and visible light excitation on ex vivo nasal skin and sebum from uninflamed acne, but not on nose surface smears or sebum from inflamed acne. Co-registered CW laser-excited anti-Stokes fluorescence and fs laser-excited multi-photon fluorescence images of PpIX powder showed similar features. In the skin samples because of the anti-Stokes effect, the NIR-induced fluorescence was presumably specific for porphyrins since there appeared to be no anti-Stokes emission signals from other typical skin fluorophores such as lipids, keratins and collagen. Anti-Stokes fluorescence under NIR CW excitation is more sensitive and specific for porphyrin detection than UV- or visible light-excited regular fluorescence and fs laser-excited multi-photon fluorescence. This approach also has higher image contrast compared to NIR fs laser-based multi-photon fluorescence imaging. The anti-Stokes fluorescence of porphyrins within sebum could potentially be applied to detecting and targeting acne lesions for treatment via fluorescence image guidance.

  9. In Situ Observations of UV-Induced Restructuring of Self-Assembled Porphyrin Monolayer on Liquid/Au(111) Interface at Molecular Level.

    PubMed

    Kim, Yongman; Doh, Won Hui; Kim, Jeongjin; Park, Jeong Young

    2018-05-29

    Porphyrin-derived molecules have received much attention for use in solar energy conversion devices, such as artificial leaves and dye-sensitized solar cells. Because of their technological importance, a molecular-level understanding of the mechanism for supramolecular structure formation in a liquid, as well as their stability under ultraviolet (UV) irradiation, is important. Here, we observed the self-assembled structure of free-base, copper(II), and nickel(II) octaethylporphyrin formed on Au(111) in a dodecane solution using scanning tunneling microscopy (STM). As evident in the STM images, the self-assembled monolayers (SAMs) of these three porphyrins on the Au(111) surface showed hexagonal close-packed structures when in dodecane solution. Under UV irradiation (λ = 365 nm), the porphyrin molecules in the SAM or the dodecane solution move extensively and form new porphyrin clusters on the Au sites that have a high degree of freedom. Consequently, the Au(111) surface was covered with disordered porphyrin clusters. However, we found that the porphyrin molecules decomposed under UV irradiation at 254 nm. Molecular-scale observation of the morphological evolution of the porphyrin SAM under UV irradiation can provide a fundamental understanding of the degradation processes of porphyrin-based energy conversion devices.

  10. Experimental and DFT studies on DNA binding and photocleavage of two cationic porphyrins. Effects of the introduction of a carboxyphenyl into pyridinium porphyrin.

    PubMed

    Zhao, Ping; Xu, Lian-Cai; Huang, Jin-Wang; Liu, Jie; Yu, Han-Cheng; Zheng, Kang-Cheng; Ji, Liang-Nian

    2008-12-15

    The DNA-binding affinities and DNA photocleavage abilities of cationic porphyrin, 5-(4-carboxyphenyl)-10,15,20-tris(4-methylpyridiniumyl)porphyrin (CTMPyP), and its reference compound meso-tetrakis(N-methyl-4-pyridiniumyl)porphyrin (H2TMPyP) have been investigated. The DNA-binding behaviors of the two compounds in NaH2PO4 buffer were compared systematically by using absorption, fluorescence and circular dichroism (CD) spectra, thermal denaturation as well as viscosity measurements. The experimental results show that CTMPyP binds to DNA in an outside binding mode, while H2TMPyP in an intercalative mode. Photocleavage experiments reveal that both two compounds employ 1O2-mediated mechanism in cleaving DNA and H2TMPyP can cleave DNA more efficiently than CTMPyP. Theoretical calculations were carried out with the density functional theory (DFT), and the calculated results indicate that the character and energies of some frontier orbitals of CTMPyP are quite different from those of H2TMPyP. These theoretical results can be used to explain their different DNA-binding modes and affinities to a certain extent.

  11. PET/PDT theranostics: synthesis and biological evaluation of a peptide-targeted gallium porphyrin.

    PubMed

    Bryden, Francesca; Savoie, Huguette; Rosca, Elena V; Boyle, Ross W

    2015-03-21

    The development of novel theranostic agents is an important step in the pathway towards personalised medicine, with the combination of diagnostic and therapeutic modalities into a single treatment agent naturally lending itself to the optimisation and personalisation of treatment. In pursuit of the goal of a molecular theranostic suitable for use as a PET radiotracer and a photosensitiser for PDT, a novel radiolabelled peptide-porphyrin conjugate targeting the α6β1-integrin has been developed. (69/71)Ga and (68)Ga labelling of an azide-functionalised porphyrin has been carried out in excellent yields, with subsequent bioconjugation to an alkyne-functionalised peptide demonstrated. α6β1-integrin expression of two cell lines has been evaluated by flow cytometry, and therapeutic potential of the conjugate demonstrated. Evaluation of the phototoxicity of the porphyrin-peptide theranostic conjugate in comparison to an untargeted control porphyrin in vitro, demonstrated significantly enhanced activity for a cell line with higher α6β1-integrin expression when compared with a cell line exhibiting lower α6β1-integrin expression.

  12. Halogen Bonding: A Powerful Tool for Modulation of Peptide Conformation

    PubMed Central

    2017-01-01

    Halogen bonding is a weak chemical force that has so far mostly found applications in crystal engineering. Despite its potential for use in drug discovery, as a new molecular tool in the direction of molecular recognition events, it has rarely been assessed in biopolymers. Motivated by this fact, we have developed a peptide model system that permits the quantitative evaluation of weak forces in a biologically relevant proteinlike environment and have applied it for the assessment of a halogen bond formed between two amino acid side chains. The influence of a single weak force is measured by detection of the extent to which it modulates the conformation of a cooperatively folding system. We have optimized the amino acid sequence of the model peptide on analogues with a hydrogen bond-forming site as a model for the intramolecular halogen bond to be studied, demonstrating the ability of the technique to provide information about any type of weak secondary interaction. A combined solution nuclear magnetic resonance spectroscopic and computational investigation demonstrates that an interstrand halogen bond is capable of conformational stabilization of a β-hairpin foldamer comparable to an analogous hydrogen bond. This is the first report of incorporation of a conformation-stabilizing halogen bond into a peptide/protein system, and the first quantification of a chlorine-centered halogen bond in a biologically relevant system in solution. PMID:28581720

  13. Use of novel metalloporphyrins as imageable tumor-targeting agents for radiation therapy

    DOEpatents

    Miura, Michiko; Slatkin, Daniel N.

    2005-10-04

    The present invention covers halogenated derivatives of boronated phorphyrins containing multiple carborane cages having the formula ##STR1## which selectively accumulate in neoplastic tissue within the irradiation volume and thus can be used in cancer therapies including, but not limited to, boron neutron-capture therapy and photodynamic therapy. The present invention also covers methods for using these halogenated derivatives of boronated porphyrins in tumor imaging and cancer treatment.

  14. Extending Halogen-based Medicinal Chemistry to Proteins

    PubMed Central

    El Hage, Krystel; Pandyarajan, Vijay; Phillips, Nelson B.; Smith, Brian J.; Menting, John G.; Whittaker, Jonathan; Lawrence, Michael C.; Meuwly, Markus; Weiss, Michael A.

    2016-01-01

    Insulin, a protein critical for metabolic homeostasis, provides a classical model for protein design with application to human health. Recent efforts to improve its pharmaceutical formulation demonstrated that iodination of a conserved tyrosine (TyrB26) enhances key properties of a rapid-acting clinical analog. Moreover, the broad utility of halogens in medicinal chemistry has motivated the use of hybrid quantum- and molecular-mechanical methods to study proteins. Here, we (i) undertook quantitative atomistic simulations of 3-[iodo-TyrB26]insulin to predict its structural features, and (ii) tested these predictions by X-ray crystallography. Using an electrostatic model of the modified aromatic ring based on quantum chemistry, the calculations suggested that the analog, as a dimer and hexamer, exhibits subtle differences in aromatic-aromatic interactions at the dimer interface. Aromatic rings (TyrB16, PheB24, PheB25, 3-I-TyrB26, and their symmetry-related mates) at this interface adjust to enable packing of the hydrophobic iodine atoms within the core of each monomer. Strikingly, these features were observed in the crystal structure of a 3-[iodo-TyrB26]insulin analog (determined as an R6 zinc hexamer). Given that residues B24–B30 detach from the core on receptor binding, the environment of 3-I-TyrB26 in a receptor complex must differ from that in the free hormone. Based on the recent structure of a “micro-receptor” complex, we predict that 3-I-TyrB26 engages the receptor via directional halogen bonding and halogen-directed hydrogen bonding as follows: favorable electrostatic interactions exploiting, respectively, the halogen's electron-deficient σ-hole and electronegative equatorial band. Inspired by quantum chemistry and molecular dynamics, such “halogen engineering” promises to extend principles of medicinal chemistry to proteins. PMID:27875310

  15. Cytochromes and iron sulfur proteins in sulfur metabolism of phototrophic bacteria

    NASA Technical Reports Server (NTRS)

    Fischer, U.

    1985-01-01

    Dissimilatory sulfur metabolism in phototrophic sulfur bacteria provides the bacteria with electrons for photosynthetic electron transport chain and, with energy. Assimilatory sulfate reduction is necessary for the biosynthesis of sulfur-containing cell components. Sulfide, thiosulfate, and elemental sulfur are the sulfur compounds most commonly used by phototrophic bacteria as electron donors for anoxygenic photosynthesis. Cytochromes or other electron transfer proteins, like high-potential-iron-sulfur protein (HIPIP) function as electron acceptors or donors for most enzymatic steps during the oxidation pathways of sulfide or thiosulfate. Yet, heme- or siroheme-containing proteins themselves undergo enzymatic activities in sulfur metabolism. Sirohemes comprise a porphyrin-like prosthetic group of sulfate reductase. eenzymatic reactions involve electron transfer. Electron donors or acceptors are necessary for each reaction. Cytochromes and iron sulfur problems, are able to transfer electrons.

  16. Comparative study of binding interactions between porphyrin systems and aromatic compounds of biological importance by multiple spectroscopic techniques: A review.

    PubMed

    Makarska-Bialokoz, Magdalena

    2018-07-05

    The specific spectroscopic and redox properties of porphyrins predestine them to fulfill the role of sensors during interacting with different biologically active substances. Monitoring of binding interactions in the systems porphyrin-biologically active compound is a key question not only in the field of physiological functions of living organisms, but also in environmental protection, notably in the light of the rapidly growing drug consumption and concurrently the production of drug effluents. Not always beneficial action of drugs on natural porphyrin systems induces to further studies, with commercially available porphyrins as the model systems. Therefore the binding process between several water-soluble porphyrins and a series of biologically active compounds (e.g. caffeine, guanine, theophylline, theobromine, xanthine, uric acid) has been studied in different aqueous solutions analyzing their absorption and steady-state fluorescence spectra, the porphyrin fluorescence lifetimes and their quantum yields. The magnitude of the binding and fluorescence quenching constants values for particular quenchers decreases in a series: uric acid > guanine > caffeine > theophylline > theobromine > xanthine. In all the systems studied there are characters of static quenching, as a consequence of the π-π-stacked non-covalent and non-fluorescent complexes formation between porphyrins and interacting compounds, accompanied simultaneously by the additional specific binding interactions. The porphyrin fluorescence quenching can be explain by the photoinduced intermolecular electron transfer from aromatic compound to the center of the porphyrin molecule, playing the role of the binding site. Presented results can be valuable for designing of new fluorescent porphyrin chemosensors or monitoring of drug traces in aqueous solutions. The obtained outcomes have also the toxicological and medical importance, providing insight into the interactions of the water

  17. Implementation of marine halogen chemistry into the Community Multiscale Air Quality (CMAQ) model

    NASA Astrophysics Data System (ADS)

    Gantt, B.; Sarwar, G.

    2017-12-01

    In two recent studies (Sarwar et al, 2015 and Gantt et al., 2017), the impact of marine halogen (bromine and iodine) chemistry on air quality has been evaluated using the Community Multiscale Air Quality (CMAQ) model. We found that marine halogen chemistry not only has the expected effect of reducing marine boundary layer ozone concentrations, but also reduces ozone in the free troposphere and inland from the coast. In Sarwar et al. (2015), the impact of the halogen chemistry without and with photochemical reactions of higher iodine oxides over the Northern Hemisphere was examined using the coarse horizontal grids of a hemispheric domain. Halogen chemistry without and with the photochemical reactions of higher iodine oxides reduces ozone over seawater by 15% and 48%, respectively. Using the results of the chemistry without the photochemical reactions of higher iodine oxides, we developed a simple first order ozone loss rate and implemented it into the public version of CMAQv52. In Gantt et al. (2017), the impact of the simple first order loss rate as well as the full halogen chemistry without photochemical reactions of higher iodine oxides over the continental United States was examined using finer horizontal grids of the regional domain and boundary conditions from the hemispheric domain with and without marine halogen chemistry. The boundary conditions obtained with the halogen chemistry as well as the simple halogen chemistry reduces ozone along the coast where CMAQ typically overpredicts the concentrations. Development of halogen chemistry in CMAQ has continued with the implementation of several heterogeneous reactions of bromine and iodine species, revised reactions of higher iodine oxides, and a refined marine halogen emissions inventory. Our latest version of halogen chemistry with photochemical reactions of higher iodine oxides reduces ozone by 23% over the seawater. This presentation will discuss the previous and ongoing implementation of revised halogen

  18. 40 CFR 721.275 - Halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Halogenated-N-(2-propenyl)-N... New Uses for Specific Chemical Substances § 721.275 Halogenated-N-(2-propenyl)-N-(substituted phenyl... identified generically as halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide (P-83-1085) is subject...

  19. 40 CFR 721.275 - Halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated-N-(2-propenyl)-N... New Uses for Specific Chemical Substances § 721.275 Halogenated-N-(2-propenyl)-N-(substituted phenyl... identified generically as halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide (P-83-1085) is subject...

  20. Graphene and Carbon-Nanotube Nanohybrids Covalently Functionalized by Porphyrins and Phthalocyanines for Optoelectronic Properties.

    PubMed

    Wang, Aijian; Ye, Jun; Humphrey, Mark G; Zhang, Chi

    2018-04-01

    In recent years, there has been a rapid growth in studies of the optoelectronic properties of graphene, carbon nanotubes (CNTs), and their derivatives. The chemical functionalization of graphene and CNTs is a key requirement for the development of this field, but it remains a significant challenge. The focus here is on recent advances in constructing nanohybrids of graphene or CNTs covalently linked to porphyrins or phthalocyanines, as well as their application in nonlinear optics. Following a summary of the syntheses of nanohybrids constructed from graphene or CNTs and porphyrins or phthalocyanines, explicit intraconjugate electronic interactions between photoexcited porphyrins/phthalocyanines and graphene/CNTs are introduced classified by energy transfer, electron transfer, and charge transfer, and their optoelectronic applications are also highlighted. The major current challenges for the development of covalently linked nanohybrids of porphyrins or phthalocyanines and carbon nanostructures are also presented. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Halogens are key cofactors in building of collagen IV scaffolds outside the cell.

    PubMed

    Brown, Kyle L; Hudson, Billy G; Voziyan, Paul A

    2018-05-01

    The purpose of this review is to highlight recent advances in understanding the molecular assembly of basement membranes, as exemplified by the glomerular basement membrane (GBM) of the kidney filtration apparatus. In particular, an essential role of halogens in the basement membrane formation has been discovered. Extracellular chloride triggers a molecular switch within non collagenous domains of collagen IV that induces protomer oligomerization and scaffold assembly outside the cell. Moreover, bromide is an essential cofactor in enzymatic cross-linking that reinforces the stability of scaffolds. Halogenation and halogen-induced oxidation of the collagen IV scaffold in disease states damage scaffold function. Halogens play an essential role in the formation of collagen IV scaffolds of basement membranes. Pathogenic damage of these scaffolds by halogenation and halogen-induced oxidation is a potential target for therapeutic interventions.

  2. Competition between Halogen, Hydrogen and Dihydrogen Bonding in Brominated Carboranes.

    PubMed

    Fanfrlík, Jindřich; Holub, Josef; Růžičková, Zdeňka; Řezáč, Jan; Lane, Paul D; Wann, Derek A; Hnyk, Drahomír; Růžička, Aleš; Hobza, Pavel

    2016-11-04

    Halogen bonds are a subset of noncovalent interactions with rapidly expanding applications in materials and medicinal chemistry. While halogen bonding is well known in organic compounds, it is new in the field of boron cluster chemistry. We have synthesized and crystallized carboranes containing Br atoms in two different positions, namely, bound to C- and B-vertices. The Br atoms bound to the C-vertices have been found to form halogen bonds in the crystal structures. In contrast, Br atoms bound to B-vertices formed hydrogen bonds. Quantum chemical calculations have revealed that halogen bonding in carboranes can be much stronger than in organic architectures. These findings open new possibilities for applications of carboranes, both in materials and medicinal chemistry. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Metal-Mediated Halogen Exchange in Aryl and Vinyl Halides: A Review

    PubMed Central

    Evano, Gwilherm; Nitelet, Antoine; Thilmany, Pierre; Dewez, Damien F.

    2018-01-01

    Halogenated arenes and alkenes are of prime importance in many areas of science, especially in the pharmaceutical, agrochemical, and chemical industries. While the simplest ones are commercially available, some of them are still hardly accessible depending on their substitution patterns and the nature of the halogen atom. Reactions enabling the selective and efficient replacement of the halogen atom of an aryl or alkenyl halide by another one, lighter, or heavier, are therefore of major importance since they can be used for example to turn a less reactive aryl/alkenyl chloride into the more reactive iodinated derivatives or, in a reversed sense, to block an undesired reactivity, for late-stage modifications or for the introduction of a radionuclide. If some halogen exchange reactions are possible with activated substrates, they usually require catalysis with metal complexes. Remarkably efficient processes have been developed for metal-mediated halogen exchange in aryl and vinyl halides: they are overviewed, in a comprehensive manner, in this review article. PMID:29755967

  4. Metal-Mediated Halogen Exchange in Aryl and Vinyl Halides: a Review

    NASA Astrophysics Data System (ADS)

    Evano, Gwilherm; Nitelet, Antoine; Thilmany, Pierre; Dewez, Damien F.

    2018-04-01

    Halogenated arenes and alkenes are of prime importance in many areas of science, especially in the pharmaceutical, agrochemical and chemical industries. While the simplest ones are commercially available, some of them are still hardly accessible depending on their substitution patterns and the nature of the halogen atom. Reactions enabling the selective and efficient replacement of the halogen atom of an aryl or alkenyl halide by another one, lighter or heavier, are therefore of major importance since they can be used for example to turn a less reactive aryl/alkenyl chloride into the more reactive iodinated derivatives or, in a reversed sense, to block an undesired reactivity, for late-stage modifications or for the introduction of a radionuclide. If some halogen exchange reactions are possible with activated substrates, they usually require catalysis with metal complexes. Remarkably efficient processes have been developed for metal-mediated halogen exchange in aryl and vinyl halides: they are overviewed, in a comprehensive manner, in this review article.

  5. Adsorption characteristics of a cationic porphyrin on nanoclay at various pH.

    PubMed

    Rice, Zachary; Bergkvist, Magnus

    2009-07-15

    Natural and synthetic porphyrin derivatives offer a range of applications including enzymatic catalysis, photosensitizers for light harvesting and chemical reactions, and molecular electronics. They exhibit unique optical spectra dominated by the presence of Soret and Q-band structures whose position and shape offer a straightforward method to characterize porphyrins in various surroundings. In many applications it is often beneficial to have porphyrins adsorbed onto a solid matrix. Applications of porphyrin-clay complexes extend to numerous biological applications including pharmaceutical drug delivery, cosmetics, and agricultural applications and thus a full understanding of porphyrin-clay surface interactions are essential. Here we investigated the adsorption behavior of meso-tetra(4-N,N,N-trimethylanilinium) porphine (TMAP) onto sodium containing, natural montmorillonite clay (Cloisite Na(+)) in characteristic biological buffers over a range of pHs (approximately 2-9). Spectroscopic analyses show a linear absorption response at acidic and basic pHs but a slight deviation at intermediate pHs. Absorption spectra for TMAP on clay showed distinct red shifts of the Soret and Q-bands compared to free TMAP for all buffer conditions indicating core pi-electron delocalization into the substituent rings. At intermediate pHs, a gradual transition between protonated/deprotonated states were seen, presumably due to higher H(+) concentration at the surface than in bulk. Results indicate TMAP adsorption to clay occurs in a monolayer fashion at low/high pH while slightly acidic/neutral pH possibly rearrange on the surface and/or form aggregates. AFM images of clay saturated with TMAP are reported and show single isolated clay sheets without aggregation, similar to clay without TMAP.

  6. The fast method of Cu-porphyrin complex synthesis for potential use in positron emission tomography imaging

    NASA Astrophysics Data System (ADS)

    Kilian, Krzysztof; Pęgier, Maria; Pyrzyńska, Krystyna

    2016-04-01

    Porphyrin based photosensitizers are useful agents for photodynamic therapy and fluorescence imaging of cancer. Additionally, porphyrins are excellent metal chelators, forming stable metalo-complexes and 64Cu isotope can serve as a positron emitter (t1/2 = 12.7 h). The other advantage of 64Cu is its decay characteristics that facilitates the use of 64Cu-porphyrin complex as a therapeutic agent. Thus, 64Cu chelation with porphyrin photosensitizer may become a simple and versatile labeling strategy for clinical positron emission tomography. The present study reports a convenient method for the synthesis of Cu complex with tetrakis(4-carboxyphenyl)porphyrin (TCPP). The experimental conditions for labeling, such as the metal-to-ligand molar ratio, pH and time of reaction were optimized to achieve a high complexation efficiency in a short period of time as possible. In order to accelerate the metallation, the use of substitution reactions of cadmium or lead porphyrin and the presence of reducing agent, such as ascorbic acid, hydroxylamine and flavonoid - morin, were evaluated. The optimum conditions for the synthesis of the copper complex were borate buffer at pH 9 with the addition of 10-fold molar excess, with respect to Cu2 + ions and TCPP and ascorbic acid which resulted in reduction of the reaction time from 30 min to below 1 min.

  7. The effect of varying halogen substituent patterns on the cytochrome P450 catalysed dehalogenation of 4-halogenated anilines to 4-aminophenol metabolites.

    PubMed

    Cnubben, N H; Vervoort, J; Boersma, M G; Rietjens, I M

    1995-05-11

    The cytochrome P450 catalysed biotransformation of 4-halogenated anilines was studied in vitro with special emphasis on the dehalogenation to 4-aminophenol metabolites. The results demonstrated that a fluorine substituent at the C4 position was more easily eliminated from the aromatic ring than a chloro-, bromo- or iodo-substituent. HPLC analysis of in vitro biotransformation patterns revealed that the dehalogenation of the C4-position was accompanied by formation of non-halogenated 4-aminophenol, without formation of NIH-shifted metabolites. Changes in the apparent Vmax for the microsomal oxidative dehalogenation appeared to correlate with the electronegativity of the halogen substituent at C4, the fluorine substituent being the one most easily eliminated. A similar decrease in the rate of dehalogenation from a fluoro- to a chloro- to a bromo- to an iodo-substituent was observed in a system with purified reconstituted cytochrome P450 IIB1, in a tertiair butyl hydroperoxide supported microsomal cytochrome P450 system as well as in a system with microperoxidase 8. This microperoxidase 8 is a haem-based mini-enzyme without a substrate binding site, capable of catalysing cytochrome P450-like reaction chemistry. Together, these results excluded the possibility that the difference in the rate of dehalogenation with a varying C4-halogen substituent arose from a change in the contribution of cytochrome P450 enzymes involved in oxidative dehalogenation with a change in the halogen substituent. Rather, they strongly suggested that the difference was indeed due to an intrinsic electronic parameter of the various C4 halogenated anilines dependent on the type of halogen substituent. Additional in vitro experiments with polyfluorinated anilines demonstrated that elimination of the C4-fluorine substituent became more difficult upon the introduction of additional electron withdrawing fluorine substituents in the aniline-ring. 19F-NMR analysis of the metabolite patterns showed

  8. Facile fabrication of Cu(II)-porphyrin MOF thin films from tetrakis(4-carboxyphenyl)porphyrin and Cu(OH)2 nanoneedle array

    NASA Astrophysics Data System (ADS)

    La, Duong Duc; Thi, Hoai Phuong Nguyen; Kim, Yong Shin; Rananaware, Anushri; Bhosale, Sheshanath V.

    2017-12-01

    Herein, we report a facile synthetic protocol to grow thin films of Cu(II) tetrakis(4-carboxyphenyl)porphyrin (CuTCPP) metal-organic frameworks (MOF) from a tetrakis(4-carboxyphenyl)porphyrin (H2TCPP) solution and the copper hydroxide (Cu(OH)2) nanoneedle array formed on a Cu substrate at room temperature. The formations of Cu-centered TCPP ligands and crystalline platelet-like Cu MOFs were successfully probed by SEM, XRD, FTIR, UV-vis and XPS. The formation process from Cu(OH)2 was monitored by using SEM images obtained at different reaction times during the first 24 h, thus suggesting the reaction pathway of Cu(OH)2 dissolution followed by the reprecipitation of CuTCPP MOFs at a near surface. In addition, the CuTCPP MOFs exhibited a high specific surface area of 408 m2/g.

  9. The relation between molecular structure and biological activity among mononitrophenols containing halogens

    USGS Publications Warehouse

    Applegate, Vernon C.; Johnson, B.G.H.; Smith, Manning A.

    1966-01-01

    The results of tests of the biological activity of certain nitrophenols containing halogen are reported. Some of these are shown to be significantly more toxic to larvae of the sea lamprey (Petromyzon marinus L.) than to fishes. It is proposed that the death of lamprey larvae exposed to these compounds results from an acute hypotension (shock) with concomitant circulatory and respiratory failure. Rainbow trout (Salmo gairdneri), on the other hand, appear to die, at higher concentrations of the toxin, due to a chemically-caused mechanical interference with respiration through the gills. A systematic series of studies of mononitrophenols containing halogens disclosed that those phenols having the nitro group in the para-position and a halogen atom or group in the meta-position are generally more toxic to lampreys than to fish. The halogens or halogen groups used in this study were fluorine, chlorine, bromine, and trifluormethyl. The same substituents in other positions only occasionally gave rise to selectively toxic compounds. The relationship between the selectively active class of nitrophenols containing halogens and other related structures is discussed.

  10. Competitive Energy and Electron Transfer in β-Functionalized Free-Base Porphyrin-Zinc Porphyrin Dimer Axially Coordinated to C60 : Synthesis, Supramolecular Formation and Excited-State Processes.

    PubMed

    Hu, Yi; Thomas, Michael B; Jinadasa, R G Waruna; Wang, Hong; D'Souza, Francis

    2017-09-18

    Simultaneous occurrence of energy and electron transfer events involving different acceptor sites in a newly assembled supramolecular triad comprised of covalently linked free-base porphyrin-zinc porphyrin dyad, H 2 P-ZnP axially coordinated to electron acceptor fullerene, has been successfully demonstrated. The dyad was connected through the β-pyrrole positions of the porphyrin macrocycle instead of the traditionally used meso-positions for better electronic communication. Interestingly, the β-pyrrole functionalization modulated the optical properties to such an extent that it was possible to almost exclusively excite the zinc porphyrin entity in the supramolecular triad. The measured binding constant for the complex with 1:1 molecular stoichiometry was in the order of 10 4  m -1 revealing moderately stable complex formation. An energy level diagram constructed using optical, electrochemical and computational results suggested that both the anticipated energy and electron events are thermodynamically feasible in the triad. Consequently, it was possible to demonstrate occurrence of excited state energy transfer to the covalently linked H 2 P, and electron transfer to the coordinated ImC 60 from studies involving steady-state and time-resolved emission, and femto- and nanosecond transient absorption studies. The estimated energy transfer was around 67 % in the dyad with a rate constant of 1.1×10 9  s -1 . In the supramolecular triad, the charge separated state was rather long-lived although it was difficult to arrive the exact lifetime of charge separated state from nanosecond transient spectral studies due to overlap of strong triplet excited signals of porphyrin in the monitoring wavelength window. Nevertheless, simultaneous occurrence of energy and electron transfer in the appropriately positioned energy and electron acceptor entities in a supramolecular triad was possible to demonstrate in the present study, a step forward to unraveling the complex

  11. Photobactericidal porphyrin-cellulose nanocrystals: synthesis, characterization, and antimicrobial properties.

    PubMed

    Feese, Elke; Sadeghifar, Hasan; Gracz, Hanna S; Argyropoulos, Dimitris S; Ghiladi, Reza A

    2011-10-10

    Adherence and survival of pathogenic bacteria on surfaces leading to concomitant transmission to new hosts significantly contributes to the proliferation of pathogens, which in turn considerably increases the threat to human health, particularly by antibiotic-resistant bacteria. Consequently, more research into effective surface disinfection and alternative materials (fabrics, plastics, or coatings) with antimicrobial and other bioactive characteristics is desirable. This report describes the synthesis and characterization of cellulose nanocrystals that were surface-modified with a cationic porphyrin. The porphyrin was appended onto the cellulose surface via the Cu(I)-catalyzed Huisgen-Meldal-Sharpless 1,3-dipolar cycloaddition having occurred between azide groups on the cellulosic surface and porphyrinic alkynes. The resulting, generally insoluble, crystalline material, CNC-Por (5), was characterized by infrared and diffusion (1)H NMR spectroscopies, gel permeation chromatography, and thermogravimetric analysis. Although only suspended, and not dissolved, in an aqueous system, CNC-Por (5) showed excellent efficacy toward the photodynamic inactivation of Mycobacterium smegmatis and Staphylococcus aureus , albeit only slight activity against Escherichia coli . The synthesis, properties, and activity of CNC-Por (5) described herein serve as a benchmark toward our overall objectives of developing novel, potent, bioactive, photobactericidal materials that are effective against a range of bacteria, with potential utilization in the health care and food preparation industries.

  12. Binding Structures of Diatomic Molecules to Co-Porphyrins on Au(111) Studied by Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Lee, Soon-Hyeong; Chang, Yun; Kim, Howon; Jang, Won; Kim, Yong-Hyun; Kahng, Se-Jong; Department Of Physics, Korea University. Collaboration; Graduate School Of Nanoscience; Technology (Wcu), Kaist Collaboration

    2013-03-01

    Axial bindings of diatomic molecules to metalloporphyrins involve in the dynamic processes of biological functions such as respiration, neurotransmission, and photosynthesis. The binding reactions are also useful in sensor applications and to control molecular spins in metalloporphyrins for spintronic applications. Here, we present the binding structures of diatomic molecules to surface-supported Co-porphyrins studied using scanning tunneling microscopy. Upon gas exposure, three-lobed structures of Co-porphyrins transformed to bright ring shapes on Au(111), whereas H2-porphyrins of dark rings remained intact. The bright rings are explained by the structures of reaction complexes where a diatomic ligand, tilted away from the axis normal to the porphyrin plane, is under precession. Our results are consistent with previous bulk experiments using X-ray diffraction and nuclear magnetic resonance spectroscopy.

  13. Differential Antioxidant Responses and Perturbed Porphyrin Biosynthesis after Exposure to Oxyfluorfen and Methyl Viologen in Oryza sativa.

    PubMed

    Pham, Nhi-Thi; Kim, Jin-Gil; Jung, Sunyo

    2015-07-21

    We compared antioxidant responses and regulation of porphyrin metabolism in rice plants treated with oxyfluorfen (OF) or methyl viologen (MV). Plants treated with MV exhibited not only greater increases in conductivity and malondialdehyde but also a greater decline in Fv/Fm, compared to plants treated with OF. MV-treated plants had greater increases in activities of superoxide dismutase (SOD) and catalase (CAT) as well as transcript levels of SODA and CATA than OF-treated plants after 28 h of the treatments, whereas increases in ascorbate peroxidase (APX) activity and transcript levels of APXA and APXB were greater in OF-treated plants. Both OF- and MV-treated plants resulted in not only down-regulation of most genes involved in porphyrin biosynthesis but also disappearance of Mg-porphyrins during the late stage of photooxidative stress. By contrast, up-regulation of heme oxygenase 2 (HO2) is possibly part of an efficient antioxidant response to compensate photooxidative damage in both treatments. Our data show that down-regulated biosynthesis and degradation dynamics of porphyrin intermediates have important roles in photoprotection of plants from perturbed porphyrin biosynthesis and photosynthetic electron transport. This study suggests that porphyrin scavenging as well as strong antioxidative activities are required for mitigating reactive oxygen species (ROS) production under photooxidative stress caused by OF and MV.

  14. Effects of Light-Emitting Diode Irradiation on Growth Characteristics and Regulation of Porphyrin Biosynthesis in Rice Seedlings.

    PubMed

    Tran, Lien Hong; Jung, Sunyo

    2017-03-16

    We examined the effects of light quality on growth characteristics and porphyrin biosynthesis of rice seedlings grown under different wavelengths from light emitting diodes (LEDs). After 10 days of exposure to various wavelengths of LEDs, leaf area and shoot biomass were greater in seedlings grown under white and blue LEDs than those of green and red LEDs. Both green and red LED treatments drastically decreased levels of protoporphyrin IX (Proto IX) and Mg-porphyrins compared to those of white LED, while levels of Mg-Proto IX monomethyl ester and protochlorophyllide under blue LED were decreased by 21% and 49%, respectively. Transcript levels of PPO1 were greatly upregulated in seedlings grown under red LED compared to white LED, whereas transcript levels of HO2 and CHLD were upregulated under blue LED. Overall, most porphyrin biosynthetic genes in the Fe-porphyrin branch remained almost constant or upregulated, while most genes in the Mg-porphyrin branch were downregulated. Expression levels of nuclear-encoded photosynthetic genes Lhcb and RbcS noticeably decreased after exposure to blue and red LEDs, compared to white LED. Our study suggests that specific wavelengths of LED greatly influence characteristics of growth in plants partly through altering the metabolic regulation of the porphyrin biosynthetic pathway, and possibly contribute to affect retrograde signaling.

  15. Substituent Effects on the [N-I-N](+) Halogen Bond.

    PubMed

    Carlsson, Anna-Carin C; Mehmeti, Krenare; Uhrbom, Martin; Karim, Alavi; Bedin, Michele; Puttreddy, Rakesh; Kleinmaier, Roland; Neverov, Alexei A; Nekoueishahraki, Bijan; Gräfenstein, Jürgen; Rissanen, Kari; Erdélyi, Máté

    2016-08-10

    We have investigated the influence of electron density on the three-center [N-I-N](+) halogen bond. A series of [bis(pyridine)iodine](+) and [1,2-bis((pyridine-2-ylethynyl)benzene)iodine](+) BF4(-) complexes substituted with electron withdrawing and donating functionalities in the para-position of their pyridine nitrogen were synthesized and studied by spectroscopic and computational methods. The systematic change of electron density of the pyridine nitrogens upon alteration of the para-substituent (NO2, CF3, H, F, Me, OMe, NMe2) was confirmed by (15)N NMR and by computation of the natural atomic population and the π electron population of the nitrogen atoms. Formation of the [N-I-N](+) halogen bond resulted in >100 ppm (15)N NMR coordination shifts. Substituent effects on the (15)N NMR chemical shift are governed by the π population rather than the total electron population at the nitrogens. Isotopic perturbation of equilibrium NMR studies along with computation on the DFT level indicate that all studied systems possess static, symmetric [N-I-N](+) halogen bonds, independent of their electron density. This was further confirmed by single crystal X-ray diffraction data of 4-substituted [bis(pyridine)iodine](+) complexes. An increased electron density of the halogen bond acceptor stabilizes the [N···I···N](+) bond, whereas electron deficiency reduces the stability of the complexes, as demonstrated by UV-kinetics and computation. In contrast, the N-I bond length is virtually unaffected by changes of the electron density. The understanding of electronic effects on the [N-X-N](+) halogen bond is expected to provide a useful handle for the modulation of the reactivity of [bis(pyridine)halogen](+)-type synthetic reagents.

  16. Substituent Effects on the [N–I–N]+ Halogen Bond

    PubMed Central

    2016-01-01

    We have investigated the influence of electron density on the three-center [N–I–N]+ halogen bond. A series of [bis(pyridine)iodine]+ and [1,2-bis((pyridine-2-ylethynyl)benzene)iodine]+ BF4– complexes substituted with electron withdrawing and donating functionalities in the para-position of their pyridine nitrogen were synthesized and studied by spectroscopic and computational methods. The systematic change of electron density of the pyridine nitrogens upon alteration of the para-substituent (NO2, CF3, H, F, Me, OMe, NMe2) was confirmed by 15N NMR and by computation of the natural atomic population and the π electron population of the nitrogen atoms. Formation of the [N–I–N]+ halogen bond resulted in >100 ppm 15N NMR coordination shifts. Substituent effects on the 15N NMR chemical shift are governed by the π population rather than the total electron population at the nitrogens. Isotopic perturbation of equilibrium NMR studies along with computation on the DFT level indicate that all studied systems possess static, symmetric [N–I–N]+ halogen bonds, independent of their electron density. This was further confirmed by single crystal X-ray diffraction data of 4-substituted [bis(pyridine)iodine]+ complexes. An increased electron density of the halogen bond acceptor stabilizes the [N···I···N]+ bond, whereas electron deficiency reduces the stability of the complexes, as demonstrated by UV-kinetics and computation. In contrast, the N–I bond length is virtually unaffected by changes of the electron density. The understanding of electronic effects on the [N–X–N]+ halogen bond is expected to provide a useful handle for the modulation of the reactivity of [bis(pyridine)halogen]+-type synthetic reagents. PMID:27265247

  17. Estimation of porphyrin concentration in the kerogen fraction of shales using high-resolution reflectance spectroscopy

    NASA Technical Reports Server (NTRS)

    Holden, Peter N.; Gaffey, Michael J.; Sundararaman, P.

    1991-01-01

    An interpretive model for estimating porphyrin concentration in bitumen and kerogen from spectral reaflectance data in the visible and near-ultraviolet region of the spectrum is derived and calibrated. Preliminary results obtained using the model are consistent with concentrations determined from the bitumen extract and suggest that 40 to 60 percent of the total porphyrin concentration remains in the kerogen after extraction of bitumen from thermally immature samples. The reflectance technique will contribute to porphyrin and kerogen studies and can be applied at its present level of development to several areas of geologic and paleo-oceanographic research.

  18. Probing ‘Spin-Forbidden’ Oxygen Atom Transfer: Gas-Phase Reactions of Chromium-Porphyrin Complexes

    PubMed Central

    Fornarini, Simonetta; Lanucara, Francesco; Warren, Jeffrey J.

    2010-01-01

    Oxygen-atom transfer reactions of metalloporphyrin species play an important role in biochemical and synthetic oxidation reactions. An emerging theme in this chemistry is that spin-state changes can play important roles, and a ‘two-state’ reactivity model has been extensively applied especially in iron-porphyrin systems. Herein we explore the gas phase oxygen-atom transfer chemistry of meso-tetrakis(pentafluorophenyl)porphyrin (TPFPP) chromium complexes, as well as some other tetradentate macrocyclic ligands. Electrospray ionization in concert with Fourier transform ion cyclotron resonance (FT-ICR) spectrometry has been used to characterize and observe reactivity of the ionic species [(TPFPP)CrIII]+ (1) and [(TPFPP)CrVO]+ (2). These are an attractive system to examine the effects of spin state change on oxygen atom transfer because the d1 CrV species are doublets while the CrIII complexes have quartet ground states with high-lying doublet excited states. In the gas phase, [(TPFPP)CrIII]+ forms adducts with a variety of neutral donors but O-atom transfer is only observed for NO2. Pyridine N-oxide adducts of 1 do yield 2 upon collision induced dissociation (CID), but the ethylene oxide, DMSO, and TEMPO analogs do not. [(TPFPP)CrVO]+ is shown by its reactivity and by CID experiments to be a terminal metal-oxo with a single vacant coordination site. It also displays limited reaction chemistry, being deoxygenated only by the very potent reductant P(OMe)3. In general, [(TPFPP)CrVO]+ species are much less reactive than the Fe and Mn analogs. Thermochemical analysis of the reactions points towards the involvement of spin issues in the lower observed reactivity of the chromium complexes. PMID:20218631

  19. Mechanistic insight of the photodynamic effect induced by tri- and tetra-cationic porphyrins on Candida albicans cells.

    PubMed

    Cormick, M Paula; Quiroga, Ezequiel D; Bertolotti, Sonia G; Alvarez, M Gabriela; Durantini, Edgardo N

    2011-10-01

    The photodynamic mechanism of action induced by 5-(4-trifluorophenyl)-10,15,20-tris(4-N,N,N-trimethylammoniumphenyl)porphyrin (TFAP(3+)), 5,10,15,20-tetrakis(4-N,N,N-trimethylammoniumphenyl)porphyrin (TMAP(4+)) and 5,10,15,20-tetrakis(4-N-methylpyridyl)porphyrin (TMPyP(4+)) was investigated on Candida albicans cells. These cationic porphyrins are effective photosensitizers, producing a ~5 log decrease of cell survival when the cultures are incubated with 5 μM photosensitizer and irradiated for 30 min with visible light. Studies under anoxic conditions indicated that oxygen is necessary for the mechanism of action of photodynamic inactivation of this yeast. Furthermore, photoinactivation of C. albicans cells was negligible in the presence of 100 mM azide ion, whereas the photocytotoxicity induced by these porphyrins increased in D(2)O. In contrast, the addition of 100 mM mannitol produced a negligible effect on the cellular phototoxicity. On the other hand, in vitro direct observation of singlet molecular oxygen, O(2)((1)Δ(g)) phosphorescence at 1270 nm was analyzed using C. albicans in D(2)O. A shorter lifetime of O(2)((1)Δ(g)) was found in yeast cellular suspensions. These cationic porphyrins bind strongly to C. albicans cells and the O(2)((1)Δ(g)) generated inside the cells is rapidly quenched by the biomolecules of the cellular microenvironment. Therefore, the results indicate that these cationic porphyrins appear to act as photosensitizers mainly via the intermediacy of O(2)((1)Δ(g)). This journal is © The Royal Society of Chemistry and Owner Societies 2011

  20. Molecular modeling on porphyrin derivatives as β5 subunit inhibitor of 20S proteasome.

    PubMed

    Arba, Muhammad; Nur-Hidayat, Andry; Ruslin; Yusuf, Muhammad; Sumarlin; Hertadi, Rukman; Wahyudi, Setyanto Tri; Surantaadmaja, Slamet Ibrahim; Tjahjono, Daryono H

    2018-06-01

    The ubiquitin-proteasome system plays an important role in protein quality control. Currently, inhibition of the proteasome has been validated as a promising approach in anticancer therapy. The 20S core particle of the proteasome harbors β5 subunit which is a crucial active site in proteolysis. Targeting proteasome β5 subunit which is responsible for the chymotrypsin-like activity of small molecules has been regarded as an important way for achieving therapeutics target. In the present study, a series of porphyrin derivatives bearing either pyridine or pyrazole rings as meso-substituents were designed and evaluated as an inhibitor for the β5 subunit of the proteasome by employing molecular docking and dynamics simulations. The molecular docking was performed with the help of AutoDock 4.2, while molecular dynamics simulation was done using AMBER 14. All compounds bound to the proteasome with similar binding modes, and each porphyrin-proteasome complex was stable during 30 ns MD simulation as indicated by root-mean-square-deviation (RMSD) value. An analysis on protein residue fluctuation of porphyrin binding demonstrates that in all complexes, porphyrin binding produces minor fluctuation on amino acid residues. The molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) free energy calculation shows that the binding affinities of mono-H 2 PyP, bis-H 2 PzP, and tetra-H 2 PyP were comparable with that of the potential inhibitor, HU10. It is noted that the electrostatic interaction increases with the number of meso-substituents, which was favourable for porphyrin binding. The present study shows that both electrostatic and van der Waals interaction are the main force which controls the interaction of porphyrin compounds with the proteasome. Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. Self-organization of porphyrin units induced by magnetic field during sol-gel polymerization.

    PubMed

    Lerouge, Frédéric; Cerveau, Geneviève; Corriu, Robert J P; Stern, Christine; Guilard, Roger

    2007-04-21

    The use of a magnetic field as a controlling factor during the hydrolysis-polycondensation of porphyrin precursors substituted by Si(OR)(3) groups, induces a self-organization of porphyrin moieties due to the stacking of these units in the hybrid material and this study also confirms the effect of the magnetic field in the nano- and micrometric organization during the kinetically controlled polycondensation process.

  2. 21 CFR 862.1595 - Porphyrins test system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Porphyrins test system. 862.1595 Section 862.1595 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Chemistry Test Systems § 862...

  3. Double-chamber electrode for spectrochemical determination of chlorine and other halogens

    USGS Publications Warehouse

    de Paiva, Azevedo; Specht, A.W.; Harner, R.S.

    1954-01-01

    A double-chamber, graphite electrode, suitable for d.c. arc determination of halogens by means of the alkaline earth halide bands, is described. An upper chamber holds the alkaline earth compound and an interconnected, lower chamber holds the halogen compound. This arrangement assures that there will be an abundance of alkaline earths in the arc by the time the halogen is volatilized from the lower chamber, and thereby promotes maximum emission of the alkaline earth halide bands. ?? 1954.

  4. REGIOSELECTIVE OXIDATIONS OF EQUILENIN DERIVATIVES CATALYZED BY A RHODIUM (III) PORPHYRIN COMPLEX-CONTRAST WITH THE MANGANESE (III) PORPHYRIN. (R826653)

    EPA Science Inventory

    Abstract

    Equilenin acetate and dihydroequilenin acetate were oxidized with iodosobenzene and a rhodium(III) porphyrin catalyst. The selectivity of the reactions differs from that with the corresponding Mn(III) catalyst, or from that of free radical chain oxidation.

  5. Photocurrent in Multilayered Assemblies of Porphyrin-Fullerene Covalent Dyads: Evidence for Channels for Charge Transport.

    PubMed

    Konev, Alexander S; Khlebnikov, Alexander F; Levin, Oleg V; Lukyanov, Daniil A; Zorin, Ivan M

    2016-04-07

    Specially designed porphyrin-fullerene dyads have been synthesized to verify literature predictions based on quantum chemistry calculations that certain porphyrin-fullerene dyads are able to self-arrange into specific structures providing channels for charge transport in a bulk mass of organic compound. According to AFM and SEM data, the newly synthesized compounds were indeed prone to some kind of self-arrangement, although to a lesser degree than was expected. A dispersion corrected DFT study of the molecular non-covalent interactions performed at the DFT-D3 (B3LYP, 6-31G*) level of theory showed that the least energy corresponded to head-to-head dimers, with close contacts of porphyrin-porphyrin and fullerene-fullerene fragments, thus providing a unit building block of the channel for charge transport. Experimental proof for the existence of channels for charge transport was obtained by observing a photocurrent in a simple photovoltaic cell. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Porphyrin mediated photo-modification of the structure and function of human serum albumin

    NASA Astrophysics Data System (ADS)

    Rozinek, Sarah C.

    Photosensitization reactions involve irradiating (with visible light) molecules with a high efficiency for either electron transfer or entering an excited triplet state (photosensitizer). Such reactions are applied to photodynamic cancer therapy, many medical laser-treatments, and a potential array of disinfection and pest elimination techniques. To understand the biophysical mechanisms of how these applications are effective at the protein level, the group of Dr. Brancaleon (UTSA) has investigated the irradiation of several dye-protein combinations, and discovered effects on protein structure and function. To further that work, we have investigated irradiation of the protein, human serum albumin (HSA), photosensitized by either protoporphyrin IX (PPIX) or meso-tetrakis(4-sulfonatophenyl)porphyrin (TSPP). HSA is the most abundant plasma protein, making it a likely substrate in PDT, and it possesses a specific binding pocket for iron-PPIX (heme) and possibly other porphyrin derivatives. The results of our research are summarized as follows. First, a thorough characterization of the binding of each photosensitizer to albumin was completed, elucidating a probable binding location for TSPP. Next, fluorescence lifetime emission of the single tryptophan residue, alongside circular dichroism, found tertiary structural changes around tryptophan and an overall 20% decrease in protein secondary structure after irradiation with TSPP bound. Finally, to determine if protein function was lost after photosensitization, size exclusion chromatography found modified albumin still recognizable by its receptor-protein, and comparative ex vivo up-take studies revealed that modified albumin is not processed the same way as native albumin in live tapeworm larva (Mesocestoides corti). Thus we found that visible light can induce partial unfolding of a protein by using a photo-activated ligand. These small structural modifications were sufficient to affect the protein's biological function.

  7. De novo design and engineering of functional metal and porphyrin-binding protein domains

    NASA Astrophysics Data System (ADS)

    Everson, Bernard H.

    In this work, I describe an approach to the rational, iterative design and characterization of two functional cofactor-binding protein domains. First, a hybrid computational/experimental method was developed with the aim of algorithmically generating a suite of porphyrin-binding protein sequences with minimal mutual sequence information. This method was explored by generating libraries of sequences, which were then expressed and evaluated for function. One successful sequence is shown to bind a variety of porphyrin-like cofactors, and exhibits light- activated electron transfer in mixed hemin:chlorin e6 and hemin:Zn(II)-protoporphyrin IX complexes. These results imply that many sophisticated functions such as cofactor binding and electron transfer require only a very small number of residue positions in a protein sequence to be fixed. Net charge and hydrophobic content are important in determining protein solubility and stability. Accordingly, rational modifications were made to the aforementioned design procedure in order to improve its overall success rate. The effects of these modifications are explored using two `next-generation' sequence libraries, which were separately expressed and evaluated. Particular modifications to these design parameters are demonstrated to effectively double the purification success rate of the procedure. Finally, I describe the redesign of the artificial di-iron protein DF2 into CDM13, a single chain di-Manganese four-helix bundle. CDM13 acts as a functional model of natural manganese catalase, exhibiting a kcat of 0.08s-1 under steady-state conditions. The bound manganese cofactors have a reduction potential of +805 mV vs NHE, which is too high for efficient dismutation of hydrogen peroxide. These results indicate that as a high-potential manganese complex, CDM13 may represent a promising first step toward a polypeptide model of the Oxygen Evolving Complex of the photosynthetic enzyme Photosystem II.

  8. Extremely weak linear electron-phonon coupling in iron-free hemeproteins studied by phase-modulated photon echo

    NASA Astrophysics Data System (ADS)

    Lin, J. W.-I.; Tada, T.; Saikan, S.; Kushida, T.; Tani, T.

    1991-10-01

    The femtosecond accumulated photon echoes in iron-free myoglobin and iron-free cytochrome-C reveal that the linear electron-phonon coupling is extremely weak in these materials. This feature also manifests itself in the absence of the Stokes shift in the fluorescence spectrum over a wide range of temperatures from liquid-helium temperatures to near room temperatures. The origin of the weak coupling is attributed to the close packing of the porphyrin chromophores into a hydrophobic environment, which is constructed out of the polypeptide chain of the protein. The present results hint at the so-called hydrophobic compartmentalization of the chromophores as one of the important factors in reducing markedly the electron-phonon coupling in dye-polymer systems.

  9. Mechanistic aspects of the photodynamic inactivation of Candida albicans induced by cationic porphyrin derivatives.

    PubMed

    Quiroga, Ezequiel D; Cormick, M Paula; Pons, Patricia; Alvarez, M Gabriela; Durantini, Edgardo N

    2012-12-01

    Photodynamic inactivation of Candida albicans produced by 5-(4-trifluorophenyl)-10,15,20-tris(4-N,N,N-trimethylammoniumphenyl)porphyrin (TFAP(3+)), 5,10,15,20-tetrakis(4-N,N,N-trimethylammoniumphenyl)porphyrin (TMAP(4+)) and 5,10,15,20-tetrakis(4-N-methylpyridyl)porphyrin (TMPyP(4+)) was investigated to obtain insight about the mechanism of cellular damage. In solution, absorption spectroscopic studies showed that these cationic porphyrins interact strongly with calf thymus DNA. The electrophoretic analysis indicated that photocleavage of DNA induced by TFAP(3+) took place after long irradiation periods (>5 h). In contrast, TMAP(4+) produced a marked reduction in DNA band after 1 h irradiation. In C. albicans, these cationic porphyrins produced a ∼3.5 log decrease in survival when the cell suspensions (10(7) cells/mL) were incubated with 5 μM photosensitizer and irradiated for 30 min with visible light (fluence 162 J/cm(2)). After this treatment, modifications of genomic DNA isolated from C. albicans cells were not found by electrophoresis. Furthermore, transmission electron microscopy showed structural changes with appearance of low density areas into the cells and irregularities in cell barriers. However, the photodamage to the cell envelope was insufficient to cause the release of intracellular biopolymers. Therefore, modifications in the cytoplasmic biomolecules and alteration in the cell barriers could be mainly involved in C. albicans photoinactivation. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  10. Elucidation of the iron(IV)–oxo intermediate in the non-haem iron halogenase SyrB2

    PubMed Central

    Wong, Shaun D.; Srnec, Martin; Matthews, Megan L.; Liu, Lei V.; Kwak, Yeonju; Park, Kiyoung; Bell, Caleb B.; Alp, E. Ercan; Zhao, Jiyong; Yoda, Yoshitaka; Kitao, Shinji; Seto, Makoto; Krebs, Carsten; Bollinger, J. Martin; Solomon, Edward I.

    2013-01-01

    SUMMARY Mononuclear non-haem iron (NHFe) enzymes catalyse a wide variety of oxidative reactions including halogenation, hydroxylation, ring closure, desaturation, and aromatic ring cleavage. These are highly important for mammalian somatic processes such as phenylalanine metabolism, production of neurotransmitters, hypoxic response, and the biosynthesis of natural products.1–3 The key reactive intermediate in the catalytic cycles of these enzymes is an S = 2 FeIV=O species, which has been trapped for a number of NHFe enzymes4–8 including the halogenase SyrB2, the subject of this study. Computational studies to understand the reactivity of the enzymatic NHFe FeIV=O intermediate9–13 are limited in applicability due to the paucity of experimental knowledge regarding its geometric and electronic structures, which determine its reactivity. Synchrotron-based nuclear resonance vibrational spectroscopy (NRVS) is a sensitive and effective method that defines the dependence of the vibrational modes of Fe on the nature of the FeIV=O active site.14–16 Here we present the first NRVS structural characterisation of the reactive FeIV=O intermediate of a NHFe enzyme. This FeIV=O intermediate reacts via an initial H-atom abstraction step, with its subsquent halogenation (native) or hydroxylation (non-native) rebound reactivity being dependent on the substrate.17 A correlation of the experimental NRVS data to electronic structure calculations indicates that the substrate is able to direct the orientation of the FeIV=O intermediate, presenting specific frontier molecular orbitals (FMOs) which can activate the selective halogenation versus hydroxylation reactivity. PMID:23868262

  11. Differential Antioxidant Responses and Perturbed Porphyrin Biosynthesis after Exposure to Oxyfluorfen and Methyl Viologen in Oryza sativa

    PubMed Central

    Pham, Nhi-Thi; Kim, Jin-Gil; Jung, Sunyo

    2015-01-01

    We compared antioxidant responses and regulation of porphyrin metabolism in rice plants treated with oxyfluorfen (OF) or methyl viologen (MV). Plants treated with MV exhibited not only greater increases in conductivity and malondialdehyde but also a greater decline in Fv/Fm, compared to plants treated with OF. MV-treated plants had greater increases in activities of superoxide dismutase (SOD) and catalase (CAT) as well as transcript levels of SODA and CATA than OF-treated plants after 28 h of the treatments, whereas increases in ascorbate peroxidase (APX) activity and transcript levels of APXA and APXB were greater in OF-treated plants. Both OF- and MV-treated plants resulted in not only down-regulation of most genes involved in porphyrin biosynthesis but also disappearance of Mg-porphyrins during the late stage of photooxidative stress. By contrast, up-regulation of heme oxygenase 2 (HO2) is possibly part of an efficient antioxidant response to compensate photooxidative damage in both treatments. Our data show that down-regulated biosynthesis and degradation dynamics of porphyrin intermediates have important roles in photoprotection of plants from perturbed porphyrin biosynthesis and photosynthetic electron transport. This study suggests that porphyrin scavenging as well as strong antioxidative activities are required for mitigating reactive oxygen species (ROS) production under photooxidative stress caused by OF and MV. PMID:26197316

  12. Halogenated naphthyl methoxy piperidines for mapping serotonin transporter sites

    DOEpatents

    Goodman, Mark M.; Faraj, Bahjat

    1999-01-01

    Halogenated naphthyl methoxy piperidines having a strong affinity for the serotonin transporter are disclosed. Those compounds can be labeled with positron-emitting and/or gamma emitting halogen isotopes by a late step synthesis that maximizes the useable lifeterm of the label. The labeled compounds are useful for localizing serotonin transporter sites by positron emission tomography and/or single photon emission computed tomography.

  13. Halogenated naphthyl methoxy piperidines for mapping serotonin transporter sites

    DOEpatents

    Goodman, M.M.; Faraj, B.

    1999-07-06

    Halogenated naphthyl methoxy piperidines having a strong affinity for the serotonin transporter are disclosed. Those compounds can be labeled with positron-emitting and/or gamma emitting halogen isotopes by a late step synthesis that maximizes the useable lifeterm of the label. The labeled compounds are useful for localizing serotonin transporter sites by positron emission tomography and/or single photon emission computed tomography.

  14. RESIDUAL RISK ASSESSMENT: HALOGENATED SOLVENTS

    EPA Science Inventory

    This source category previously subjected to a technology-based standard will be examined to determine if health or ecological risks are significant enough to warrant further regulation for Halogenated Solvent Degreasing Facilities. These assessments utilize existing models and d...

  15. Cyclic Bis-porphyrin-Based Flexible Molecular Containers: Controlling Guest Arrangements and Supramolecular Catalysis by Tuning Cavity Size.

    PubMed

    Mondal, Pritam; Sarkar, Sabyasachi; Rath, Sankar Prasad

    2017-05-23

    Three cyclic zinc(II) bis-porphyrins (CB) with highly flexible linkers are employed as artificial molecular containers that efficiently encapsulate/coordinate various aromatic aldehydes within their cavities. Interestingly, the arrangements of guests and their reactivity inside the molecular clefts are significantly influenced by the cavity size of the cyclic containers. In the presence of polycyclic aromatic aldehydes, such as 3-formylperylene, as a guest, the cyclic bis-porphyrin host with a smaller cavity (CB1) forms a 1:1 sandwich complex. Upon slightly increasing the spacer length and thereby the cavity size, the cyclic host (CB2) encapsulates two molecules of 3-formylperylene that are also stacked together due to strong π-π interactions between them and CH-π interactions with the porphyrin rings. However, in the cyclic host (CB3) with an even larger cavity, two metal centers of the bis-porphyrin axially coordinate two molecules of 3-formylperylene within its cavity. Different arrangements of guest inside the cyclic bis-porphyrin hosts are investigated by using UV/Vis, ESI-MS, and 1 H NMR spectroscopy, along with X-ray structure determination of the host-guest complexes. Moreover, strong binding of guests within the cyclic bis-porphyrin hosts support the robust nature of the host-guest assemblies in solution. Such preferential binding of the bis-porphyrinic cavity towards aromatic aldehydes through encapsulation/coordination has been employed successfully to catalyze the Knoevenagel condensation of a series of polycyclic aldehydes with active methylene compounds (such as Meldrum's acid and 1, 3-dimethylbarbituric acid) under ambient conditions. Interestingly, the yields of the condensed products significantly increase upon increasing spacer lengths of the cyclic bis-porphyrins because more substrates can then be encapsulated within the cavity. Such controllable cavity size of the cyclic containers has profound implications for constructing highly

  16. Reduction of halogenated ethanes by green rust.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    O'Loughlin, E. J.; Burris, D. R.; Environmental Research

    Green rusts, mixed Fe{sup II}/Fe{sup III} hydroxide minerals present in many suboxic environments, have been shown to reduce a number of organic and inorganic contaminants. The reduction of halogenated ethanes was examined in aqueous suspensions of green rust, both alone and with the addition of Ag{sup I} (AgGR) and Cu{sup II} (CuGR). Hexachloroethane (HCA), pentachloroethane (PCA), 1,1,1,2-tetrachloroethane (1,1,1,2-TeCA), 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA), 1,1,1-trichloroethane (1,1,1-TCA), 1,1,2-trichloroethane (1,1,2-TCA), 1,1-dichloroethane (1,1-DCA), and 1,2-dibromoethane were reduced in the presence of green rust alone, AgGR, or CuGR; only 1,2-dichloroethane and chloroethane were nonreactive. The reduction was generally more rapid for more highly substituted ethanes than for ethanesmore » having fewer halogen groups (HCA > PCA > 1,1,1,2-TeCA > 1,1,1-TCA > 1,1,2,2-TeCA > 1,1,2-TCA > 1,1-DCA), and isomers with the more asymmetric distributions of halogen groups were more rapidly reduced than the isomer with greater symmetry (e.g., 1,1,1-TCA > 1,1,2-TCA). The addition of Ag{sup I} or Cu{sup II} to green rust suspensions resulted in a substantial increase in the rate of halogenated ethane reduction as well as significant differences in the product distributions with respect to green rust alone.« less

  17. XAFS Debye-Waller Factors Temperature-Dependent Expressions for Fe+2-Porphyrin Complexes

    NASA Astrophysics Data System (ADS)

    Dimakis, Nicholas; Bunker, Grant

    2007-02-01

    We present an efficient and accurate method for directly calculating single and multiple scattering X-ray absorption fine structure (XAFS) thermal Debye-Waller factors for Fe+2 -porphiryn complexes. The number of multiple scattering Debye-Waller factors on metal porphyrin centers exceeds the number of available parameters that XAFS experimental data can support during fitting with simulated spectra. Using the Density Functional Theory (DFT) under the hybrid functional of X3LYP, phonon normal mode spectrum properties are used to express the mean square variation of the half-scattering path length for a Fe+2 -porphiryn complex as a function of temperature for the most important single and multiple scattering paths of the complex thus virtually eliminating them from the fitting procedure. Modeled calculations are compared with corresponding values obtained from DFT-built and optimized Fe+2 -porphyrin bis-histidine structure as well as from experimental XAFS spectra previously reported. An excellent agreement between calculated and reference Debye-Waller factors for Fe+2-porphyrins is obtained.

  18. Preparation, electrochemical and spectral properties of free-base and manganese N-methyl-pyridylethynyl porphyrins.

    PubMed

    Lin, Ching-Yao; Chen, Yen-Chuan; Yao, Chi-Wen; Huang, Sung-Chou; Cheng, Yi-Hui

    2008-02-14

    Two series of free-base and manganese N-methyl-pyridylethynyl-5,15-biphenyl porphyrins were synthesized, and their UV-Visible, electrochemical and spectro-electrochemical properties were studied. Cyclic voltammetry experiments showed positive shifts in the reduction potentials and the UV-Visible spectra showed significant red-shifts in the absorption wavelengths of these porphyrins, indicating the effects of N-methyl-pyridylethynyl substituents.

  19. Binding interactions of halogenated bisphenol A with mouse PPARα: In vitro investigation and molecular dynamics simulation.

    PubMed

    Zhang, Jie; Li, Tiezhu; Wang, Tuoyi; Guan, Tianzhu; Yu, Hansong; Li, Zhuolin; Wang, Yongzhi; Wang, Yongjun; Zhang, Tiehua

    2018-02-01

    The binding of bisphenol A (BPA) and its halogenated derivatives (halogenated BPAs) to mouse peroxisome proliferator-activated receptor α ligand binding domain (mPPARα-LBD) was examined by a combination of in vitro investigation and in silico simulation. Fluorescence polarization (FP) assay showed that halogenated BPAs could bind to mPPARα-LBD* as the affinity ligands. The calculated electrostatic potential (ESP) illustrated the different charge distributions of halogenated BPAs with altered halogenation patterns. As electron-attracting substituents, halogens decrease the positive electrostatic potential and thereby have a significant influence on the electrostatic interactions of halogenated BPAs with mPPARα-LBD*. The docking results elucidated that hydrophobic and hydrogen-bonding interactions may also contribute to stabilize the binding of the halogenated BPAs to their receptor molecule. Comparison of the calculated binding energies with the experimentally determined affinities yielded a good correlation (R 2 =0.6659) that could provide a rational basis for designing environmentally benign chemicals with reduced toxicities. This work can potentially be used for preliminary screening of halogenated BPAs. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Porphyrins as Corrosion Inhibitors for N80 Steel in 3.5% NaCl Solution: Electrochemical, Quantum Chemical, QSAR and Monte Carlo Simulations Studies.

    PubMed

    Singh, Ambrish; Lin, Yuanhua; Quraishi, Mumtaz A; Olasunkanmi, Lukman O; Fayemi, Omolola E; Sasikumar, Yesudass; Ramaganthan, Baskar; Bahadur, Indra; Obot, Ime B; Adekunle, Abolanle S; Kabanda, Mwadham M; Ebenso, Eno E

    2015-08-18

    The inhibition of the corrosion of N80 steel in 3.5 wt. % NaCl solution saturated with CO2 by four porphyrins, namely 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphyrin (HPTB), 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphyrin (T4PP), 4,4',4″,4‴-(porphyrin-5,10,15,20-tetrayl)tetrakis(benzoic acid) (THP) and 5,10,15,20-tetraphenyl-21H,23H-porphyrin (TPP) was studied using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, scanning electrochemical microscopy (SECM) and scanning electron microscopy (SEM) techniques. The results showed that the inhibition efficiency, η% increases with increasing concentration of the inhibitors. The EIS results revealed that the N80 steel surface with adsorbed porphyrins exhibited non-ideal capacitive behaviour with reduced charge transfer activity. Potentiodynamic polarization measurements indicated that the studied porphyrins acted as mixed type inhibitors. The SECM results confirmed the adsorption of the porphyrins on N80 steel thereby forming a relatively insulated surface. The SEM also confirmed the formation of protective films of the porphyrins on N80 steel surface thereby protecting the surface from direct acid attack. Quantum chemical calculations, quantitative structure activity relationship (QSAR) were also carried out on the studied porphyrins and the results showed that the corrosion inhibition performances of the porphyrins could be related to their EHOMO, ELUMO, ω, and μ values. Monte Carlo simulation studies showed that THP has the highest adsorption energy, while T4PP has the least adsorption energy in agreement with the values of σ from quantum chemical calculations.

  1. Synthesis of Five‐Porphyrin Nanorings by Using Ferrocene and Corannulene Templates

    PubMed Central

    Liu, Pengpeng; Hisamune, Yutaka; Peeks, Martin D.; Odell, Barbara; Gong, Juliane Q.; Herz, Laura M.

    2016-01-01

    Abstract The smallest and most strained member of a family of π‐conjugated cyclic porphyrin oligomers was synthesized by using pentapyridyl templates based on ferrocene and corannulene. Both templates are effective for directing the synthesis of the butadiyne‐linked cyclic pentamer, despite the fact that the radii of their N5 donor sets are too small by 0.5 Å and 0.9 Å, respectively (from DFT calculations). The five‐porphyrin nanoring exhibits a structured absorption spectrum and its fluorescence extends to 1200 nm, reflecting strong π conjugation and Herzberg–Teller vibronic coupling. PMID:27213825

  2. Synthesis and characterization of novel pyrene-dendronized porphyrins exhibiting efficient fluorescence resonance energy transfer: optical and photophysical properties.

    PubMed

    Zaragoza-Galán, Gerardo; Fowler, Michael A; Duhamel, Jean; Rein, Regis; Solladié, Nathalie; Rivera, Ernesto

    2012-07-31

    A novel series of pyrene dendronized porphyrins bearing two and four pyrenyl groups (Py(2)-TMEG1 and Py(4)-TMEG2) were successfully synthesized. First and second generation Fréchet type dendrons (Py(2)-G1OH and Py(4)-G2OH) were prepared from 1-pyrenylbutanol and 3,5-dihydroxybenzyl alcohol. These compounds were further linked to a trimesitylphenylporphyrin containing a butyric acid spacer via an esterification reaction to obtain the desired products. Dendrons and dendronized porphyrins were fully characterized by FTIR and (1)H NMR spectroscopy and their molecular weights were determined by matrix-assisted laser desorption ionization time of flight mass spectrometry. Their optical and photophysical properties were studied by absorption and fluorescence spectroscopies. The formation of dynamic excimers was detected in the pyrene-labeled dendrons, with more excimer being produced in the higher generation dendron. The fluorescence spectra of the pyrene dendronized porphyrins exhibited a significant decrease in the amount of pyrene monomer and excimer emission, jointly with the appearance of a new emission band at 661 nm characteristic of porphyrin emission, an indication that fluorescence resonance energy transfer (FRET) occurred from one of the excited pyrene species to the porphyrin. The FRET efficiency was found to be almost quantitative ranging between 97% and 99% depending on the construct. Model Free analysis of the fluorescence decays acquired with the pyrene monomer, excimer, and porphyrin core established that only residual pyrene excimer formation in the dendrons could occur before FRET from the excited pyrene monomer to the ground-state porphyrin core.

  3. Porphyrin-based Photocatalytic Nanolithography

    PubMed Central

    Bearinger, Jane P.; Stone, Gary; Dugan, Lawrence C.; El Dasher, Bassem; Stockton, Cheryl; Conway, James W.; Kuenzler, Tobias; Hubbell, Jeffrey A.

    2009-01-01

    Nanoarray fabrication is a multidisciplinary endeavor encompassing materials science, chemical engineering, and biology. We formed nanoarrays via a new technique, porphyrin-based photocatalytic nanolithography. The nanoarrays, with controlled features as small as 200 nm, exhibited regularly ordered patterns and may be appropriate for (a) rapid and parallel proteomics screening of immobilized biomolecules, (b) protein-protein interactions, and/or (c) biophysical and molecular biology studies involving spatially dictated ligand placement. We demonstrated protein immobilization utilizing nanoarrays fabricated via photocatalytic nanolithography on silicon substrates where the immobilized proteins are surrounded by a non-fouling polymer background. PMID:19406753

  4. Investigation of reactive halogens in the Arctic using a mobile instrumental laboratory

    NASA Astrophysics Data System (ADS)

    Custard, K.; Shepson, P. B.; Stephens, C. R.

    2011-12-01

    Custard, K kcustard@purdue.edu Chemistry Department, Purdue University, West Lafayette, IN, USA Shepson, P pshepson@purdue.edu Chemistry Department, Purdue University, West Lafayette, IN, USA Stephens, C thompscr@purdue.edu Chemistry Department, Purdue University, West Lafayette, IN, USA Investigation of the chemistry of reactive halogens in ice-covered regions is important because of its significant impact on atmospheric composition. Halogens in the Arctic react with ozone and gaseous elemental mercury to sometimes completely deplete them from the ambient atmosphere, at least during polar springtime. There is much uncertainty about the sources and concentrations of these atmospheric halogens in the Arctic, particularly with respect to chlorine. To gain a better understanding of them, we have developed a method to simultaneously measure the concentrations of BrOx and ClOx radicals using a flowtube method. The method involves reaction of the halogen atom with a halogenated alkene, to produce a multiply halogenated characteristic ketone product, which is then detected via GC/ECD. The system was deployed at Barrow, AK, using a mobile instrumental laboratory so that measurements could be made from multiple locations along the sea ice. In this paper we will discuss laboratory evaluation of the flowtube method, and present preliminary data from Barrow, AK, during the spring 2011 deployment.

  5. van der Waals interactions are critical in Car-Parrinello molecular dynamics simulations of porphyrin-fullerene dyads.

    PubMed

    Karilainen, Topi; Cramariuc, Oana; Kuisma, Mikael; Tappura, Kirsi; Hukka, Terttu I

    2015-04-05

    The interplay between electrostatic and van der Waals (vdW) interactions in porphyrin-C60 dyads is still under debate despite its importance in influencing the structural characteristics of such complexes considered for various applications in molecular photovoltaics. In this article, we sample the conformational space of a porphyrin-C60 dyad using Car-Parrinello molecular dynamics simulations with and without empirical vdW corrections. Long-range vdW interactions, which are poorly described by the commonly used density functional theory functionals, prove to be essential for a proper dynamics of the dyad moieties. Inclusion of vdW corrections brings porphyrin and C60 close together in an orientation that is in agreement with experimental observations. The structural differences arising from the vdW corrections are shown to be significant for several properties and potentially less important for others. Additionally, our Mulliken population analysis reveals that contrary to the common belief, porphyrin is not the primary electron donating moiety for C60 . In the considered dyad, fullerene's affinity for electrons is primarily satisfied by charge transfer from the amide group of the linker. However, we show that in the absence of another suitable bound donor, C60 can withdraw electrons from porphyrin if it is sufficiently close. © 2015 Wiley Periodicals, Inc.

  6. Engineering of Porphyrin Molecules for Use as Effective Cathode Interfacial Modifiers in Organic Solar Cells of Enhanced Efficiency and Stability.

    PubMed

    Tountas, Marinos; Verykios, Apostolis; Polydorou, Ermioni; Kaltzoglou, Andreas; Soultati, Anastasia; Balis, Nikolaos; Angaridis, Panagiotis A; Papadakis, Michael; Nikolaou, Vasilis; Auras, Florian; Palilis, Leonidas C; Tsikritzis, Dimitris; Evangelou, Evangelos K; Gardelis, Spyros; Koutsoureli, Matroni; Papaioannou, George; Petsalakis, Ioannis D; Kennou, Stella; Davazoglou, Dimitris; Argitis, Panagiotis; Falaras, Polycarpos; Coutsolelos, Athanassios G; Vasilopoulou, Maria

    2018-06-20

    In the present work, we effectively modify the TiO 2 electron transport layer of organic solar cells with an inverted architecture using appropriately engineered porphyrin molecules. The results show that the optimized porphyrin modifier bearing two carboxylic acids as the anchoring groups and a triazine electron-withdrawing spacer significantly reduces the work function of TiO 2 , thereby reducing the electron extraction barrier. Moreover, the lower surface energy of the porphyrin-modified substrate results in better physical compatibility between the latter and the photoactive blend. Upon employing porphyrin-modified TiO 2 electron transport layers in PTB7:PC 71 BM-based organic solar cells we obtained an improved average power conversion efficiency up to 8.73%. Importantly, porphyrin modification significantly increased the lifetime of the devices, which retained 80% of their initial efficiency after 500 h of storage in the dark. Because of its simplicity and efficacy, this approach should give tantalizing glimpses and generate an impact into the potential of porphyrins to facilitate electron transfer in organic solar cells and related devices.

  7. Concentration-dependent multiple chirality transition in halogen-bond-driven 2D self-assembly process

    NASA Astrophysics Data System (ADS)

    Miao, Xinrui; Li, Jinxing; Zha, Bao; Miao, Kai; Dong, Meiqiu; Wu, Juntian; Deng, Wenli

    2018-03-01

    The concentration-dependent self-assembly of iodine substituted thienophenanthrene derivative (5,10-DITD) is investigated at the 1-octanic acid/graphite interface using scanning tunneling microscopy. Three kinds of chiral arrangement and transition of 2D molecular assembly mainly driven by halogen bonding is clearly revealed. At high concentration the molecules self-assembled into a honeycomb-like chiral network. Except for the interchain van der Waals forces, this pattern is stabilized by intermolecular continuous Cdbnd O⋯I⋯S halogen bonds in each zigzag line. At moderate concentration, a chiral kite-like nanoarchitecture are observed, in which the Cdbnd O⋯I⋯S and I⋯Odbnd C halogen bonds, along with the molecule-solvent Cdbnd O⋯I⋯H halogen bonds are the dominated forces to determine the structural formation. At low concentration, the molecules form a chiral cyclic network resulting from the solvent coadsorption mainly by molecule-molecule Cdbnd O⋯I⋯S halogen bonds and molecule-solvent Cdbnd O⋯I⋯H halogen bonds. The density of molecular packing becomes lower with the decreasing of the solution concentration. The solution-concentration dependent self-assembly of thienophenanthrene derivative with iodine and ester chain moieties reveals that the type of intermolecular halogen bond and the number of the co-adsorbing 1-octanic acids by molecule-solvent Cdbnd O⋯I⋯H halogen bonds determine the formation and transformation of chirality. This research emphasizes the role of different types of halogen (I) bonds in the controllable supramolecular structures and provides an approach for the fabrication of chirality.

  8. New ZnO@Cardanol Porphyrin Composite Nanomaterials with Enhanced Photocatalytic Capability under Solar Light Irradiation

    PubMed Central

    Ribeiro, Viviane Gomes Pereira; Marcelo, Ana Maria Pereira; da Silva, Kássia Teixeira; da Silva, Fernando Luiz Firmino; Mota, João Paulo Ferreira; do Nascimento, João Paulo Costa; Sombra, Antonio Sérgio Bezerra; Clemente, Claudenilson da Silva; Mazzetto, Selma Elaine

    2017-01-01

    This work describes the synthesis, characterization, and photocatalytic activity of new composite nanomaterials based on ZnO nanostructures impregnated by lipophlilic porphyrins derived from cashew nut shell liquid (CNSL). The obtained nanomaterials were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and steady-state photoluminescence spectra (PL). The results confirm nanostructures showing average diameter of 55 nm and an improved absorption in the visible region. Further, the FTIR analysis proved the existence of non-covalent interactions between the porphyrin molecules and ZnO. The photocatalytic activity of prepared photocatalysts was investigated by degradation of rhodamine B (RhB) in aqueous solution under visible light irradiation and natural sunlight. It was demonstrated that the photocatalytic activity increases in the presence of the porphyrins and, also, depends on the irradiation source. The development of composite photocatalysts based on porphyrins derived from CNSL provides an alternative approach to eliminate efficiently toxic wastes from water under ambient conditions. PMID:28934117

  9. Covalent functionalization of reduced graphene oxide with porphyrin by means of diazonium chemistry for nonlinear optical performance

    NASA Astrophysics Data System (ADS)

    Wang, Aijian; Yu, Wang; Huang, Zhipeng; Zhou, Feng; Song, Jingbao; Song, Yinglin; Long, Lingliang; Cifuentes, Marie P.; Humphrey, Mark G.; Zhang, Long; Shao, Jianda; Zhang, Chi

    2016-03-01

    Reduced graphene oxide (RGO)-porphyrin (TPP) nanohybrids (RGO-TPP 1 and RGO-TPP 2) were prepared by two synthetic routes that involve functionalization of the RGO using diazonium salts. The microscopic structures, morphology, photophysical properties and nonlinear optical performance of the resultant RGO-TPP nanohybrids were investigated. The covalent bonding of the porphyrin-functionalized-RGO nanohybrid materials was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimetric analysis. Attachment of the porphyrin units to the surface of the RGO by diazotization significantly improves the solubility and ease of processing of these RGO-based nanohybrid materials. Ultraviolet/visible absorption and steady-state fluorescence studies indicate considerable π-π interactions and effective photo-induced electron and/or energy transfer between the porphyrin moieties and the extended π-system of RGO. The nonlinear optical properties of RGO-TPP 1 and RGO-TPP 2 were investigated by open-aperture Z-scan measurements at 532 nm with both 4 ns and 21 ps laser pulses, the results showing that the chemical nanohybrids exhibit improved nonlinear optical properties compared to those of the benchmark material C60, and the constituent RGO or porphyrins.

  10. [Study on the aggregation behavior of cationic porphyrins and their interaction with ctDNA].

    PubMed

    Ma, Hong-Min; Chen, Xin; Sun, Shu-Ting; Zhang, Li-Na; Wu, Dan; Zhu, Pei-Hua; Li, Yan; Du, Bin; Wei, Qin

    2009-02-01

    Interest in the interaction between cationic porphyrins, particularly derivatives of meso-tetra(N-methylpyridinium-4-yl) porphyrin(TMPyP), and DNA abounds because they are versatile DNA-binding agents that could find application in photodynamic therapy, cancer detection, artificial nucleases, virus inhibition and so on. The interaction of two water-soluble cationic porphyrins, meso-tetrakis(4-N, N, N-trimethylanilinium) porphyrin (TMAP) and 5-phenyl-10,15,20-tris[4-(N-methyl) pyridinium]porphyrin (TriMPyP), with calf thymus DNA (ctDNA) was studied by UV-Vis absorption spectroscopy, fluorescence spectroscopy and resonance light scattering technique. TriMPyP forms aggregate in water due to the molecular asymmetry while TMAP exists as monomers. At lower concentrations of ctDNA (R > 1, R = c(TMAP)/c(DNA) base pair), the interaction of TMAP with DNA leads to significant hypochromicity and bathochromic shift of absorption spectra. And the fluorescence of TMAP was quenched while it showed enhanced resonance light scattering signals. But the extent of enhancement of resonance light scattering signals is very small, so the aggregate of TMAP is not very high. These observations indicate the self-stacking of TMAP along the DNA surface. At higher concentrations of ctDNA (R < 1), TMAP association with DNA is via outside binding which is accompanied with hyperchromic effect and fluorescence enhancement while the resonance light scattering signals is reduced. DNA addition decreases the fluorescence intensity of TriMPyP and it shifts the peak to the higher wavelengths (red shift). The interaction with DNA promotes the aggregation of TriMPyP and no simple outside binding is observed even at higher concentrations of ctDNA. The steric effect of molecular distortion constrains the intercalation or further binding to DNA. The effect of ionic strength on the interaction was investigated at two DNA concentrations, 1.2 and 24.0 micromol x L(-1), for TMAP. The Interactions of both

  11. The severity of hereditary porphyria is modulated by the porphyrin exporter and Lan antigen ABCB6

    PubMed Central

    Fukuda, Yu; Cheong, Pak Leng; Lynch, John; Brighton, Cheryl; Frase, Sharon; Kargas, Vasileios; Rampersaud, Evadnie; Wang, Yao; Sankaran, Vijay G.; Yu, Bing; Ney, Paul A.; Weiss, Mitchell J.; Vogel, Peter; Bond, Peter J.; Ford, Robert C.; Trent, Ronald J.; Schuetz, John D.

    2016-01-01

    Hereditary porphyrias are caused by mutations in genes that encode haem biosynthetic enzymes with resultant buildup of cytotoxic metabolic porphyrin intermediates. A long-standing open question is why the same causal porphyria mutations exhibit widely variable penetrance and expressivity in different individuals. Here we show that severely affected porphyria patients harbour variant alleles in the ABCB6 gene, also known as Lan, which encodes an ATP-binding cassette (ABC) transporter. Plasma membrane ABCB6 exports a variety of disease-related porphyrins. Functional studies show that most of these ABCB6 variants are expressed poorly and/or have impaired function. Accordingly, homozygous disruption of the Abcb6 gene in mice exacerbates porphyria phenotypes in the Fechm1Pas mouse model, as evidenced by increased porphyrin accumulation, and marked liver injury. Collectively, these studies support ABCB6 role as a genetic modifier of porphyria and suggest that porphyrin-inducing drugs may produce excessive toxicities in individuals with the rare Lan(−) blood type. PMID:27507172

  12. Porphyrin metabolisms in human skin commensal Propionibacterium acnes bacteria: potential application to monitor human radiation risk.

    PubMed

    Shu, M; Kuo, S; Wang, Y; Jiang, Y; Liu, Y-T; Gallo, R L; Huang, C-M

    2013-01-01

    Propionibacterium acnes (P. acnes), a Gram-positive anaerobic bacterium, is a commensal organism in human skin. Like human cells, the bacteria produce porphyrins, which exhibit fluorescence properties and make bacteria visible with a Wood's lamp. In this review, we compare the porphyrin biosynthesis in humans and P. acnes. Also, since P. acnes living on the surface of skin receive the same radiation exposure as humans, we envision that the changes in porphyrin profiles (the absorption spectra and/or metabolism) of P. acnes by radiation may mirror the response of human cells to radiation. The porphyrin profiles of P. acnes may be a more accurate reflection of radiation risk to the patient than other biodosimeters/biomarkers such as gene up-/down-regulation, which may be non-specific due to patient related factors such as autoimmune diseases. Lastly, we discuss the challenges and possible solutions for using the P. acnes response to predict the radiation risk.

  13. Fabrication of a TiO2@porphyrin nanofiber hybrid material: a highly efficient photocatalyst under simulated sunlight irradiation

    NASA Astrophysics Data System (ADS)

    La, Duong Duc; Rananaware, Anushri; Phuong Nguyen Thi, Hoai; Jones, Lathe; Bhosale, Sheshanath V.

    2017-03-01

    The solar spectrum consists of 8% UV radiation, while 45% of solar energy is from visible light. It is therefore desirable to fabricate a hybrid material which is able to harvest energy from a wide range of photons from the sun for applications such as solar cells, photovoltaics, and photocatalysis. In this study we report on the fabrication of a TiO2@porphyrin hybrid material by surfactant-assisted co-assembly of monomeric porphyrin molecules with TiO2 nanoparticles. The obtained TiO2@porphyrin composite shows excellent integration of TiO2 particles with diameters of 15-30 nm into aggregated porphyrin nanofibers, which have a width of 70-90 nm and are several µm long. SEM, XPS, XRD, FTIR, UV-Vis and fluorescence spectroscopy were employed to characterize the TiO2@TCPP hybrid material. This material exhibits efficient photocatalytic performance under simulated sunlight, due to synergistic photocatalytic activities of the porphyrin aggregates in visible light and TiO2 particles in the UV region. A plausible mechanism for photocatalytic degradation is also proposed and discussed.

  14. Fine tuning of graphene properties by modification with aryl halogens

    NASA Astrophysics Data System (ADS)

    Bouša, D.; Pumera, M.; Sedmidubský, D.; Šturala, J.; Luxa, J.; Mazánek, V.; Sofer, Z.

    2016-01-01

    Graphene and its derivatives belong to one of the most intensively studied materials. The radical reaction using halogen derivatives of arene-diazonium salts can be used for effective control of graphene's electronic properties. In our work we investigated the influence of halogen atoms (fluorine, chlorine, bromine and iodine) as well as their position on the benzene ring towards the electronic and electrochemical properties of modified graphenes. The electronegativity as well as the position of the halogen atoms on the benzene ring has crucial influence on graphene's properties due to the inductive and mesomeric effects. The results of resistivity measurement are in good agreement with the theoretical calculations of electron density within chemically modified graphene sheets. Such simple chemical modifications of graphene can be used for controllable and scalable synthesis of graphene with tunable transport properties.Graphene and its derivatives belong to one of the most intensively studied materials. The radical reaction using halogen derivatives of arene-diazonium salts can be used for effective control of graphene's electronic properties. In our work we investigated the influence of halogen atoms (fluorine, chlorine, bromine and iodine) as well as their position on the benzene ring towards the electronic and electrochemical properties of modified graphenes. The electronegativity as well as the position of the halogen atoms on the benzene ring has crucial influence on graphene's properties due to the inductive and mesomeric effects. The results of resistivity measurement are in good agreement with the theoretical calculations of electron density within chemically modified graphene sheets. Such simple chemical modifications of graphene can be used for controllable and scalable synthesis of graphene with tunable transport properties. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06295k

  15. Halogen-free benzoxazine based curable compositions for high TG applications

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tietze, Roger; Nguyen, Yen-Loan

    The present invention provides a halogen-free curable composition including a benzoxazine monomer, at least one epoxy resin, a catalyst, a toughening agent and a solvent. The halogen-free curable composition is especially suited for use in automobile and aerospace applications since the composition, upon curing, produces a composite having a high glass transition temperature.

  16. Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins

    DOE PAGES

    Bediako, D. Kwabena; Solis, Brian H.; Dogutan, Dilek K.; ...

    2014-10-08

    Here, the hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the hydrogen evolution reaction (HER). We now show improved HER activity of Ni compared with Co hangman porphyrins. Cyclic voltammogram data and simulations, together with computational studies using density functional theory, implicate a shift in electrokinetic zone between Co and Ni hangman porphyrins due to a change in the PCET mechanism. Unlike the Co hangman porphyrin, the Ni hangman porphyrin does not require reduction to the formally metal(0) species before protonation by weak acids in acetonitrile. We concludemore » that protonation likely occurs at the Ni(I) state followed by reduction, in a stepwise proton transfer–electron transfer pathway. Spectroelectrochemical and computational studies reveal that upon reduction of the Ni(II) compound, the first electron is transferred to a metal-based orbital, whereas the second electron is transferred to a molecular orbital on the porphyrin ring.« less

  17. Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins

    PubMed Central

    Bediako, D. Kwabena; Solis, Brian H.; Dogutan, Dilek K.; Roubelakis, Manolis M.; Maher, Andrew G.; Lee, Chang Hoon; Chambers, Matthew B.; Hammes-Schiffer, Sharon; Nocera, Daniel G.

    2014-01-01

    The hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the hydrogen evolution reaction (HER). We now show improved HER activity of Ni compared with Co hangman porphyrins. Cyclic voltammogram data and simulations, together with computational studies using density functional theory, implicate a shift in electrokinetic zone between Co and Ni hangman porphyrins due to a change in the PCET mechanism. Unlike the Co hangman porphyrin, the Ni hangman porphyrin does not require reduction to the formally metal(0) species before protonation by weak acids in acetonitrile. We conclude that protonation likely occurs at the Ni(I) state followed by reduction, in a stepwise proton transfer–electron transfer pathway. Spectroelectrochemical and computational studies reveal that upon reduction of the Ni(II) compound, the first electron is transferred to a metal-based orbital, whereas the second electron is transferred to a molecular orbital on the porphyrin ring. PMID:25298534

  18. Controls on porphyrin concentrations of Pennsylvanian organic-rich shales, Western U.S.A.

    USGS Publications Warehouse

    Clayton, J.L.; Michael, G.E.

    1990-01-01

    Organic-rich black shales of Middle Pennsylvanian (Desmoinesian) age occur over much of the central U.S. and as far west as the northern Denver and southeastern Powder River basins. Total organic carbon contents (Corg) are commonly greater than 10 wt %. Porphyrin concentrations (vanadyl + nickel) are as high as 40000 ppm relative to extractable bitumen. In bulk, the organic matter contained in the shales is mostly type II and III (Rock-Eval hydrogen indexes 200-400 mg of hydrocarbons/g of Corg). The finding of high porphyrin concentrations in type III organic matter is unusual but can be explained by a depositional model wherein high preservation of primary organic production (water column photosynthesis) is combined with substantial input of allochthonous organic matter. The allochthonous organic matter (low porphyrin concentration) may come from erosion during advance of the sea across the area or from fluvial transport from shore.

  19. Electron transport property of cobalt-centered porphyrin-armchair graphene nanoribbon (AGNR) junction

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mondal, Rajkumar; Sarkar, Utpal, E-mail: utpalchemiitkgp@yahoo.com

    2015-06-24

    We have investigated the electron transport properties of Cobalt-centered (Co-centered) porphyrin molecule using the density functional theory and non-equilibrium greens function method. Here we have reported transmission coefficient as well as current voltage characteristics of Co-centered porphyrine molecule connected between armchair graphene nanoribbons. It has been found that at low bias region i.e., 0 V to 0.3 V it does not contribute any current. Gradual increase of bias voltage results different order of magnitude of current in different bias region.

  20. Stepwise π-extension of meso-alkylidenyl porphyrins through sequential 1,3-dipolar cycloaddition and redox reactions.

    PubMed

    Park, Dowoo; Jeong, Seung Doo; Ishida, Masatoshi; Lee, Chang-Hee

    2014-08-25

    Several regioselectively π-extended, pyrrole fused porphyrinoids have been synthesized by the 1,3-dipolar cycloaddition of meso-alkylidene-(benzi)porphyrins. Pd(II) complexes gave oxidation resistant, bis-pyrrole fused adducts. The repeated 1,3-dipolar cycloaddition followed by oxidation-reduction of pentaphyrin analogs afforded π-extended porphyrin analogs.

  1. Halogen bonding (X-bonding): A biological perspective

    PubMed Central

    Scholfield, Matthew R; Zanden, Crystal M Vander; Carter, Megan; Ho, P Shing

    2013-01-01

    The concept of the halogen bond (or X-bond) has become recognized as contributing significantly to the specificity in recognition of a large class of halogenated compounds. The interaction is most easily understood as primarily an electrostatically driven molecular interaction, where an electropositive crown, or σ-hole, serves as a Lewis acid to attract a variety of electron-rich Lewis bases, in analogous fashion to a classic hydrogen bonding (H-bond) interaction. We present here a broad overview of X-bonds from the perspective of a biologist who may not be familiar with this recently rediscovered class of interactions and, consequently, may be interested in how they can be applied as a highly directional and specific component of the molecular toolbox. This overview includes a discussion for where X-bonds are found in biomolecular structures, and how their structure–energy relationships are studied experimentally and modeled computationally. In total, our understanding of these basic concepts will allow X-bonds to be incorporated into strategies for the rational design of new halogenated inhibitors against biomolecular targets or toward molecular engineering of new biological-based materials. PMID:23225628

  2. Synthesis of metallic nanoshells on porphyrin-stabilized emulsions

    DOEpatents

    Wang, Haorong [Albuquerque, NM; Song, Yujiang [Albuquerque, NM; Shelnutt, John A [Tijeras, NM; Medforth, Craig J [Winters, CA

    2011-12-13

    Metal nanostructures formed by photocatalytic interfacial synthesis using a porphyrin-stabilized emulsion template and the method for making the nanostructures. Catalyst-seeded emulsion droplets are employed as templates for hollow-nanoshell growth. The hollow metal nanospheres may be formed with or without inclusions of other materials.

  3. Process for oxidation of hydrogen halides to elemental halogens

    DOEpatents

    Lyke, Stephen E.

    1992-01-01

    An improved process for generating an elemental halogen selected from chlorine, bromine or iodine, from a corresponding hydrogen halide by absorbing a molten salt mixture, which includes sulfur, alkali metals and oxygen with a sulfur to metal molar ratio between 0.9 and 1.1 and includes a dissolved oxygen compound capable of reacting with hydrogen halide to produce elemental halogen, into a porous, relatively inert substrate to produce a substrate-supported salt mixture. Thereafter, the substrate-supported salt mixture is contacted (stage 1) with a hydrogen halide while maintaining the substrate-supported salt mixture during the contacting at an elevated temperature sufficient to sustain a reaction between the oxygen compound and the hydrogen halide to produce a gaseous elemental halogen product. This is followed by purging the substrate-supported salt mixture with steam (stage 2) thereby recovering any unreacted hydrogen halide and additional elemental halogen for recycle to stage 1. The dissolved oxygen compound is regenerated in a high temperature (stage 3) and an optical intermediate temperature stage (stage 4) by contacting the substrate-supported salt mixture with a gas containing oxygen whereby the dissolved oxygen compound in the substrate-supported salt mixture is regenerated by being oxidized to a higher valence state.

  4. Porphyrins and pheomelanins contribute to the reddish juvenal plumage of black-shouldered kites.

    PubMed

    Negro, Juan J; Bortolotti, Gary R; Mateo, Rafael; García, Isabel M

    2009-07-01

    Porphyrins are a widespread group of pigments in nature, but, contrary to melanins and carotenoids, their occurrence as plumage colorants seems to be anecdotal and their function, if any, is unknown. Using thin-layer chromatography and high pressure liquid chromatography, we have found coproporphyrin III, the same porphyrin type previously reported in owls, in the plumage of nestling black-shouldered kites (Elanus caeruleus). The first plumage grown at the nest in this species includes reddish-brown contour feathers in the upperparts, and particularly in the breast area, which fade during the weeks-long post-fledging period to become either gray or white consistent with the definitive adult plumage. In these reddish feathers, we have also found small amounts of pheomelanins and traces of eumelanin. The contribution of each pigment to the final colour perceived by birds or other animals is unknown. In white and grey feathers of the same species no porphyrin was found, and only traces of eumelanin were detected in the grey ones. The fact that the reddish feathers are only found in the juvenal plumage, when individuals are vulnerable in an open nest, leads us to hypothesize a camouflage role for this ephemeral plumage. As porphyrins are involved, although not exclusively, we can for the first time ascribe them a function in the plumage of birds.

  5. Influence of aqueous media properties on aggregation and solubility of four structurally related meso-porphyrin photosensitizers evaluated by spectrophotometric measurements.

    PubMed

    Sobczyński, J; Tønnesen, H H; Kristensen, S

    2013-02-01

    Porphyrin photosensitizers tend to aggregate in aqueous solutions even in the micromolar concentration range. This is a challenge during formulation of e.g., parenteral preparations for photodynamic cancer therapy, or preparations for local or topical administration in antimicrobial photodynamic therapy. Monomerization is essential to achieve biocompatible drug formulations of high bioavailability and physiological response (i.e., photoreactivity) and low toxicity. The aggregation and solubilization of four structurally related meso-tetraphenyl porphyrin photosensitizers with nonionic (4-hydroxy), anionic (4-sulphonate; 4-carboxy) and cationic (4-trimethylanilinium) substituents were evaluated in various vehicles by use of UV-Vis spectroscopy. Substituents, overall charge and charge distribution influenced the pKa-values and interaction of the porphyrins with different solvents, excipients and impurities. Modification of medium polarity and solubilization by the nonionic surfactant Tween 80 adjusted the acid-base equilibria and increased the solubility by reduction of porphyrin aggregation. The selected porphyrins were sensitive towards ionic strength, temperature and inorganic impurities to various extents. The results will be further used during development of parenteral and topical formulations of porphyrin photosensitizers for use in photodynamic therapy of cancer and bacterial infections.

  6. A metagenomic-based survey of microbial (de)halogenation potential in a German forest soil

    PubMed Central

    Weigold, Pascal; El-Hadidi, Mohamed; Ruecker, Alexander; Huson, Daniel H.; Scholten, Thomas; Jochmann, Maik; Kappler, Andreas; Behrens, Sebastian

    2016-01-01

    In soils halogens (fluorine, chlorine, bromine, iodine) are cycled through the transformation of inorganic halides into organohalogen compounds and vice versa. There is evidence that these reactions are microbially driven but the key enzymes and groups of microorganisms involved are largely unknown. Our aim was to uncover the diversity, abundance and distribution of genes encoding for halogenating and dehalogenating enzymes in a German forest soil by shotgun metagenomic sequencing. Metagenomic libraries of three soil horizons revealed the presence of genera known to be involved in halogenation and dehalogenation processes such as Bradyrhizobium or Pseudomonas. We detected a so far unknown diversity of genes encoding for (de)halogenating enzymes in the soil metagenome including specific and unspecific halogenases as well as metabolic and cometabolic dehalogenases. Genes for non-heme, no-metal chloroperoxidases and haloalkane dehalogenases were the most abundant halogenase and dehalogenase genes, respectively. The high diversity and abundance of (de)halogenating enzymes suggests a strong microbial contribution to natural halogen cycling. This was also confirmed in microcosm experiments in which we quantified the biotic formation of chloroform and bromoform. Knowledge on microorganisms and genes that catalyze (de)halogenation reactions is critical because they are highly relevant to industrial biotechnologies and bioremediation applications. PMID:27353292

  7. Density functional IR, Raman, and VCD spectra of halogen substituted β-lactams

    NASA Astrophysics Data System (ADS)

    Rode, Joanna E.; Dobrowolski, Jan Cz.

    2003-06-01

    Halogenoazetidinones are important as synthetic intermediates for preparation of halogen β-lactam (2-azetidinone) antibiotics and as building blocks for carbohydrates and amino acids. In this paper, we consider the influence of the halogen atom, substituted at the C4 position of the 2-azetidinone ring, on the geometry, IR, Raman, and vibrational circular dichroism spectra. The vibrational spectra were calculated for the chiral 4-( R)-X-2-azetidinone (X=F, Cl or Br) molecules at the B3PW91/aug-cc-pVTZ level. It was shown that the geometry of the molecules studied do not change much upon the change of the halogen atom. In case of the vibrational spectra, the position but even more the intensities depend strongly on the kind of halogen substituent.

  8. Synthesis and Photophysical Properties of Sulfonamidophenyl Porphyrins as Models for Activatable Photosensitizers

    PubMed Central

    Bhaumik, Jayeeta; Weissleder, Ralph; McCarthy, Jason R.

    2009-01-01

    The ability to localize agents to specific anatomic sites remains an important aspect in designing more efficient therapeutics. Light-activated therapies, in particular, allow for the focal ablation of target tissues and cells. In order to increase the specificity of these agents, stimuli-activated systems have been developed, which are non-phototoxic in the absence of activation. To this end, we propose a novel paradigm for excited state quenching and activation based upon the direct conjugation of quenching moieties to the porphyrinic macrocycle. Model compounds, based upon meso-(p-aminophenyl)porphyrins were synthesized bearing 1 to 4 sulfonamide-linked 2,4-dinitrobenzene. The singlet oxygen and fluorescence quantum yields of these compounds were obtained and compared, as well as the kinetics of activation with relevant activating agents. In addition, methods were developed to further modify the porphyrin in order to modulate the polarity and effect conjugation to biomolecules or nanoparticulate scaffolds. These systems may prove useful in the treatment of a number of disease states, such as cancer and bacterial infection. PMID:19610602

  9. New porphyrin-polyoxometalate hybrid materials: synthesis, characterization and investigation of catalytic activity in acetylation reactions.

    PubMed

    Araghi, Mehdi; Mirkhani, Valiollah; Moghadam, Majid; Tangestaninejad, Shahram; Mohammdpoor-Baltork, Iraj

    2012-10-14

    New hybrid complexes based on covalent interaction between 5,10,15,20-tetrakis(4-aminophenyl)porphyrinatozinc(II) and 5,10,15,20-tetrakis(4-aminophenyl)porphyrinatotin(IV) chloride, and a Lindqvist-type polyoxometalate, Mo(6)O(19)(2-), were prepared. These new porphyrin-polyoxometalate hybrid materials were characterized by (1)H NMR, FT IR and UV-Vis spectroscopic methods and cyclic voltammetry. These spectro- and electrochemical studies provided several spectral data for synthesis of these compounds. Cyclic voltammetry showed the influence of the polyoxometalate on the redox process of the porphyrin ring. The catalytic activity of tin(IV)porphyrin-hexamolybdate hybrid material was investigated in the acetylation of alcohols and phenols with acetic anhydride. The reusability of this catalyst was also investigated.

  10. Multi-modular, tris(triphenylamine) zinc porphyrin-zinc phthalocyanine-fullerene conjugate as a broadband capturing, charge stabilizing, photosynthetic 'antenna-reaction center' mimic.

    PubMed

    Kc, Chandra B; Lim, Gary N; D'Souza, Francis

    2015-04-21

    A broadband capturing, charge stabilizing, photosynthetic antenna-reaction center model compound has been newly synthesized and characterized. The model compound is comprised of a zinc porphyrin covalently linked to three units of triphenylamine entities and a zinc phthalocyanine entity. The absorption and fluorescence spectra of zinc porphyrin complemented that of zinc phthalocyanine offering broadband coverage. Stepwise energy transfer from singlet excited triphenylamine to zinc porphyrin, and singlet excited zinc porphyrin to zinc phthalocyanine (kENT ∼ 10(11) s(-1)) was established from spectroscopic and time-resolved transient absorption techniques. Next, an electron acceptor, fullerene was introduced via metal-ligand axial coordination to both zinc porphyrin and zinc phthalocyanine centers, and they were characterized by spectroscopic and electrochemical techniques. An association constant of 4.9 × 10(4) M(-1) for phenylimidazole functionalized fullerene binding to zinc porphyrin, and 5.1 × 10(4) M(-1) for it binding to zinc phthalocyanine was obtained. An energy level diagram for the occurrence of different photochemical events within the multi-modular donor-acceptor conjugate was established from spectral and electrochemical data. Unlike the previous zinc porphyrin-zinc phthalocyanine-fullerene conjugates, the newly assembled donor-acceptor conjugate has been shown to undergo the much anticipated initial charge separation from singlet excited zinc porphyrin to the coordinated fullerene followed by a hole shift process to zinc phthalocyanine resulting in a long-lived charge separated state as revealed by femto- and nanosecond transient absorption spectroscopic techniques. The lifetime of the final charge separated state was about 100 ns.

  11. Shedding lights on the flexible-armed porphyrins: Human telomeric G4 DNA interaction and cell photocytotoxicity research.

    PubMed

    Sun, Xiang-Yu; Zhao, Ping; Jin, Shu-Fang; Liu, Min-Chao; Wang, Xia-Hong; Huang, Yu-Min; Cheng, Zhen-Feng; Yan, Si-Qi; Li, Yan-Yu; Chen, Ya-Qing; Zhong, Yan-Mei

    2017-08-01

    DNA polymorphism exerts a fascination on a large scientific community. Without crystallographic structural data, clarification of the binding modes between G-quadruplex (G4) and ligand (complex) is a challenging job. In the present work, three porphyrin compounds with different flexible carbon chains (arms) were designed, synthesized and characterized. Their binding, folding and stabilizing abilities to human telomeric G4 DNA structures were comparatively researched. Positive charges at the end of the flexible carbon chains seem to be favorable for the DNA-porphyrin interactions, which were evidenced by the spectral results and further confirmed by the molecular docking calculations. Biological function analysis demonstrated that these porphyrins show no substantial inhibition to Hela, A549 and BEL 7402 cancer cell lines under dark while exhibit broad inhibition under visible light. This significantly enhanced photocytotoxicity relative to the dark control is an essential property of photochemotherapeutic agents. The feature of the flexible arms emerges as critical influencing factors in the cell photocytotoxicity. Moreover, an ROS-mediated mitochondrial dysfunction pathway was suggested for the cell apoptosis induced by these flexible-armed porphyrins. It is found that the porphyrins with positive charges located at the end of the flexible arms represent an exciting opportunity for photochemotherapeutic anti-cancer drug design. Copyright © 2017. Published by Elsevier B.V.

  12. Covalent functionalization of reduced graphene oxide with porphyrin by means of diazonium chemistry for nonlinear optical performance

    PubMed Central

    Wang, Aijian; Yu, Wang; Huang, Zhipeng; Zhou, Feng; Song, Jingbao; Song, Yinglin; Long, Lingliang; Cifuentes, Marie P.; Humphrey, Mark G.; Zhang, Long; Shao, Jianda; Zhang, Chi

    2016-01-01

    Reduced graphene oxide (RGO)-porphyrin (TPP) nanohybrids (RGO-TPP 1 and RGO-TPP 2) were prepared by two synthetic routes that involve functionalization of the RGO using diazonium salts. The microscopic structures, morphology, photophysical properties and nonlinear optical performance of the resultant RGO-TPP nanohybrids were investigated. The covalent bonding of the porphyrin-functionalized-RGO nanohybrid materials was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimetric analysis. Attachment of the porphyrin units to the surface of the RGO by diazotization significantly improves the solubility and ease of processing of these RGO-based nanohybrid materials. Ultraviolet/visible absorption and steady-state fluorescence studies indicate considerable π-π interactions and effective photo-induced electron and/or energy transfer between the porphyrin moieties and the extended π-system of RGO. The nonlinear optical properties of RGO-TPP 1 and RGO-TPP 2 were investigated by open-aperture Z-scan measurements at 532 nm with both 4 ns and 21 ps laser pulses, the results showing that the chemical nanohybrids exhibit improved nonlinear optical properties compared to those of the benchmark material C60, and the constituent RGO or porphyrins. PMID:27011265

  13. Non-aqueous primary cell

    NASA Astrophysics Data System (ADS)

    James, S. D.; Smith, P. H.; Oneill, K. M.; Wilson, M. H.

    1986-05-01

    This patent application relates to electrochemical cells and especially to high-energy, liquid cathode, non-aqueous lithium electrochemical cells free from highly toxic materials. A non-aqueous lithium electrochemical cell is described which includes a halocarbon cathode depolarizer which is 1,2-dichloroethane, 1.1,2-trichloroethane, 1,1,2,2-tetrachloroethane, 1,2-dichloro-1,1-difluoroethane or mixtures thereof and a cathode catalyst which is copper, rhodium, palladium, cobalt phthalocyanine, nickel phthalocyanine, iron phthalocyanine, a cobalt tetraaza-(14)-annulene, a nickel tetraaza-(14)-annulene, a iron tetraaza-(14)-annulene, a cobalt porphyrin, a nickel porphyrin, a iron porphyrin, or a mixture thereof.

  14. Comparative VOCs sensing performance for conducting polymer and porphyrin functionalized carbon nanotubes based sensors

    NASA Astrophysics Data System (ADS)

    Datta, Kunal; Rushi, Arti; Ghosh, Prasanta; Shirsat, Mahendra

    2018-05-01

    We report sensors for detection of ethyl alcohol, a prominent volatile organic compound (VOC). Single walled carbon nanotubes were selected as main sensing backbone. As efficiency of sensor is dependent upon the choice of sensing materials, the performances of conducting polymer and porphyrin based sensors were compared. Chemiresistive sensing modality was adopted to observe the performance of sensors. It has been found that porphyrin based sensor shows higher affinity towards ethyl alcohol.

  15. Charge-transfer state and large first hyperpolarizability constant in a highly electronically coupled zinc and gold porphyrin dyad.

    PubMed

    Fortage, Jérôme; Scarpaci, Annabelle; Viau, Lydie; Pellegrin, Yann; Blart, Errol; Falkenström, Magnus; Hammarström, Leif; Asselberghs, Inge; Kellens, Ruben; Libaers, Wim; Clays, Koen; Eng, Mattias P; Odobel, Fabrice

    2009-09-14

    We report the synthesis and the characterizations of a novel dyad composed of a zinc porphyrin (ZnP) linked to a gold porphyrin (AuP) through an ethynyl spacer. The UV/Vis absorption spectrum and the electrochemical properties clearly reveal that this dyad exhibits a strong electronic coupling in the ground state as evidenced by shifted redox potentials and the appearance of an intense charge-transfer band localized at lambda = 739 nm in dichloromethane. A spectroelectrochemical study of the dyad along with the parent homometallic system (i.e., ZnP-ZnP and AuP-AuP) was undertaken to determine the spectra of the reduced and oxidized porphyrin units. Femtosecond transient absorption spectroscopic analysis showed that the photoexcitation of the heterometallic dyad leads to an ultrafast formation of a charge-separated state ((+)ZnP-AuP(*)) that displays a particularly long lifetime (tau = 4 ns in toluene) for such a short separation distance. The molecular orbitals of the dyad were determined by DFT quantum-chemical calculations. This theoretical study confirms that the observed intense band at lambda = 739 nm corresponds to an interporphyrin charge-transfer transition from the HOMO orbital localized on the zinc porphyrin to LUMO orbitals localized on the gold porphyrin. Finally, a Hyper-Rayleigh scattering study shows that the dyad possesses a large first molecular hyperpolarizability coefficient (beta = 2100x10(-30) esu at lambda = 1064 nm), thus highlighting the valuable nonlinear optical properties of this new type of push-pull porphyrin system.

  16. "Spider"-shaped porphyrins with conjugated pyridyl anchoring groups as efficient sensitizers for dye-sensitized solar cells.

    PubMed

    Stangel, Christina; Bagaki, Anthi; Angaridis, Panagiotis A; Charalambidis, Georgios; Sharma, Ganesh D; Coutsolelos, Athanasios G

    2014-11-17

    Two novel "spider-shaped" porphyrins, meso-tetraaryl-substituted 1PV-Por and zinc-metalated 1PV-Zn-Por, bearing four oligo(p-phenylenevinylene) (oPPV) pyridyl groups with long dodecyloxy chains on the phenyl groups, have been synthesized. The presence of four pyridyl groups in both porphyrins, which allow them to act as anchoring groups upon coordination to various Lewis acid sites, the conjugated oPPV bridges, which offer the possibility of electronic communication between the porphyrin core and the pyridyl groups, and the dodecyloxy groups, which offer the advantage of high solubility in a variety of organic solvents of different polarities and could prevent porphyrin aggregation, renders porphyrins 1PV-Por and 1PV-Zn-Por very promising sensitizers for dye-sensitized solar cells (DSSCs). Photophysical measurements, together with electrochemistry experiments and density functional theory calculations, suggest that both porphyrins have frontier molecular orbital energy levels that favor electron injection and dye regeneration in DSSCs. Solar cells sensitized by 1PV-Por and 1PV-Zn-Por were fabricated, and it was found that they show power conversion efficiencies (PCEs) of 3.28 and 5.12%, respectively. Photovoltaic measurements (J-V curves) together with incident photon-to-electron conversion efficiency spectra of the two cells reveal that the higher PCE value of the DSSC based on 1PV-Zn-Por is ascribed to higher short-circuit current (Jsc), open-circuit voltage (Voc), and dye loading values. Emission spectra and electrochemistry experiments suggest a greater driving force for injection of the photogenerated electrons into the TiO2 conduction band for 1PV-Zn-Por rather than its free-base analogue. Furthermore, electrochemical impedance spectroscopy measurements prove that the utilization of 1PV-Zn-Por as a sensitizer offers a high charge recombination resistance and, therefore, leads to a longer electron lifetime.

  17. Halogenated Natural Products in Dolphins: Brain-Blubber Distribution and Comparison with Halogenated Flame Retardants.

    PubMed

    Barón, E; Hauler, C; Gallistl, C; Giménez, J; Gauffier, P; Castillo, J J; Fernández-Maldonado, C; de Stephanis, R; Vetter, W; Eljarrat, E; Barceló, D

    2015-08-04

    Halogenated natural products (MHC-1, TriBHD, TetraBHD, MeO-PBDEs, Q1, and related PMBPs) and halogenated flame retardants (PBDEs, HBB, Dec 602, Dec 603, and DP) in blubber and brain are reported from five Alboran Sea delphinids (Spain). Both HNPs and HFRs were detected in brain, implying that they are able to surpass the blood-brain barrier and reach the brain, which represents a new finding for some compounds, such as Q1 and PMBPs, MHC-1, TriBHD, TetraBHD, or Dec 603. Moreover, some compounds (TetraBHD, BDE-153, or HBB) presented higher levels in brain than in blubber. This study evidence the high concentrations of HNPs in the marine environment, especially in top predators. It shows the importance of further monitoring these natural compounds and evaluating their potential toxicity, when most studies focus on anthropogenic compounds only. While no bioaccumulation was found for ∑HNPs, ∑HFRs increased significantly with body size for both common and striped dolphins. Studies evaluating BBB permeation mechanisms of these compounds together with their potential neurotoxic effects in dolphins are recommended.

  18. Sorption of halogenated phenols and pharmaceuticals to biochar: affecting factors and mechanisms.

    PubMed

    Oh, Seok-Young; Seo, Yong-Deuk

    2016-01-01

    The feasibility of using biochar as a sorbent to remove nine halogenated phenols (2,4-dichlorophenol, 2,4-dibromophenol, 2,4-difluorophenol, 2-chlorophenol, 4-chlorophenol, 2-bromophenol, 4-bromophenol, 2-fluorophenol, and 4-fluorophenol) and two pharmaceuticals (triclosan and ibuprofen) from water was examined through a series of batch experiments. Types of biochar, synthesized using various biomasses including fallen leaves, rice straw, corn stalk, used coffee grounds, and biosolids, were evaluated. Compared to granular activated carbon (GAC), most of the biochar samples did not effectively remove halogenated phenols or pharmaceuticals from water. The increase in pH and deprotonation of phenols in biochar systems may be responsible for its ineffectiveness at this task. When pH was maintained at 4 or 7, the sorption capacity of biochar was markedly increased. Considering maximum sorption capacity and properties of sorbents and sorbates, it appears that the sorption capacity of biochar for halogenated phenols is related to the surface area and carbon content of the biochar and the hydrophobicity of halogenated phenols. In the cases of triclosan and ibuprofen, the sorptive capacities of GAC, graphite, and biochars were also significantly affected by pH, according to the point of zero charge (PZC) of sorbents and deprotonation of the pharmaceuticals. Pyrolysis temperature did not affect the sorption capacity of halogenated phenols or pharmaceuticals. Based on the experimental observations, some biochars are good candidates for removal of halogenated phenols, triclosan, and ibuprofen from water and soil.

  19. Spectroscopic studies of porphyrin functionalized multiwalled carbon nanotubes and their interaction with TiO2 nanoparticles surface

    NASA Astrophysics Data System (ADS)

    Zannotti, Marco; Giovannetti, Rita; D'Amato, Chiara Anna; Rommozzi, Elena

    2016-01-01

    UV-vis and fluorescence investigations about the non-covalent interaction, in ethanolic solutions, of multi-wall carbon nanotube (MWCNT) with Coproporphyrin-I, and its Cu(II) and Zn(II) complexes (MCPIs) have been reported. Evidence of binding between MWCNTs and porphyrins was discovered from spectral adsorption decrease with respect to free porphyrins and by the exhibition of photoluminescence quenching with respect to free porphyrins demonstrating that MWCNT@MCPIs are potential donor-acceptor complexes. Equilibrium and kinetic aspects in the interactions with monolayer transparent TiO2 thin films with the obtained MWCNT@MCPIs are clarified showing their effective adsorption by porphyrin links on the TiO2 monolayer support, with respect to not only MWCNTs, according to the Langmuir model and with pseudo-first-order kinetics. Morphological description of the adsorption of MWCNT@MCPIs on TiO2 with scanning electron microscopy has been reported. The obtained experimental evidences describe therefore MWCNT@MCPIs as potential sensitizers in the DSSC (Dye-Sensitized Solar Cell) applications.

  20. Temporal dynamics of halogenated organic compounds in Marcellus Shale flowback.

    PubMed

    Luek, Jenna L; Harir, Mourad; Schmitt-Kopplin, Philippe; Mouser, Paula J; Gonsior, Michael

    2018-06-01

    The chemistry of hydraulic fracturing fluids and wastewaters is complex and is known to vary by operator, geologic formation, and fluid age. A time series of hydraulic fracturing fluids, flowback fluids, and produced waters was collected from two adjacent Marcellus Shale gas wells for organic chemical composition analyses using ultrahigh resolution mass spectrometry. Hierarchical clustering was used to compare and extract ions related to different fluid ages and many halogenated organic molecular ions were identified in flowback fluids and early produced waters based on exact mass. Iodinated organic compounds were the dominant halogen class in these clusters and were nearly undetectable in hydraulic fracturing fluid prior to injection. The iodinated ions increased in flowback and remained elevated after ten months of well production. We suggest that these trends are mainly driven by dissolved organic matter reacting with reactive halogen species formed abiotically through oxidizing chemical additives applied to the well and biotically via iodide-oxidizing bacteria. Understanding the implications of these identified halogenated organic compounds will require future investigation in to their structures and environmental fate. Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. Fluorescent porphyrin with an increased uptake in peripheral blood cell subpopulations from colon cancer patients.

    PubMed

    Constantin, Carolina; Neagu, Monica

    2015-01-01

    The intrinsic fluorescence of synthetic or natural porphyrins is regarded as an attractive characteristic exploited for assisting early cancer diagnosis and/or tumor localization. Single tumor cells circulating in the blood stream can be considered a major step in depicting dissemination of primary tumors, an event of clinical relevance for prognosis, staging or therapy monitoring of cancer. The third leading cause of cancer death in men is colorectal cancer and the hematogenous spreading of primary tumor cells is one of the main events in metastasis of this type of cancer. Hidden in the myriad of circulating blood cells, tumor cells need both a sensitive and affordable detection technique. 5- (3-methoxy)-4-methoxycarbonylphenyl)-10, 15, 20-tris-(4- methoxycarbonylphenyl) - 21, 23-H porphyne is a synthetic porphyrin with a noticeable preference of accumulation in peripheral blood mononuclear cells isolated from cancer patients as assessed by flow cytometry analysis. In addition, we found distinct accumulation of porphyrin depending on cancer type (cutaneous melanoma versus colorectal cancer). These data lead to the possibility of identifying circulating cells based on preferential accumulation of this new porphyrin in circulating tumor cells because, even accumulated in low percentage of cells the registered intensity of fluorescence was high. Selecting the genetic markers for circulating tumor cells is an option, but high costs and high level of know-how can be somewhat a hurdle for a rapid evaluation. Thus our approach with a new porphyrin can be developed in an accurate and innovative fast tracking method for circulating cancer cells, at least in colorectal cancer patients.

  2. Cross-reactivity of Halogenated Platinum Salts

    EPA Science Inventory

    Halogenated platinum (Pt) salts are well-known respiratory sensitizers associated with the development of asthma. People may be exposed to a variety of platinum compounds in different contexts (e.g. occupationally, automobile exhaust). Published reports suggest that sensitizati...

  3. Process for removing halogenated aliphatic and aromatic compounds from petroleum products

    DOEpatents

    Googin, John M.; Napier, John M.; Travaglini, Michael A.

    1983-01-01

    A process for removing halogenated aliphatic and aromatic compounds, e.g., polychlorinated biphenyls, from petroleum products by solvent extraction. The halogenated aliphatic and aromatic compounds are extracted from a petroleum product into a polar solvent by contacting the petroleum product with the polar solvent. The polar solvent is characterized by a high solubility for the extracted halogenated aliphatic and aromatic compounds, a low solubility for the petroleum product and considerable solvent power for polyhydroxy compound. The preferred polar solvent is dimethylformamide. A miscible compound, such as, water or a polyhydroxy compound, is added to the polar extraction solvent to increase the polarity of the polar extraction solvent. The halogenated aliphatic and aromatic compounds are extracted from the highly-polarized mixture of water or polyhydroxy compound and polar extraction solvent into a low polar or nonpolar solvent by contacting the water or polyhydroxy compound-polar solvent mixture with the low polar or nonpolar solvent. The halogenated aliphatic and aromatic compounds and the low polar or nonpolar solvent are separated by physical means, e.g., vacuum evaporation. The polar and nonpolar solvents are recovered from recycling. The process can easily be designed for continuous operation. Advantages of the process include that the polar solvent and a major portion of the nonpolar solvent can be recycled, the petroleum products are reclaimable and the cost for disposing of waste containing polychlorinated biphenyls is significantly reduced.

  4. 2.0 Angstrom Structure of Prostaglandin H2 Synthase-1 Reconstituted with a Manganese Porphyrin Cofactor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gupta,K.; Selinsky, B.; Loll, P.

    2006-01-01

    Prostaglandin H{sub 2} synthase (EC 1.14.99.1) is a clinically important drug target that catalyzes two key steps in the biosynthesis of the eicosanoid hormones. The enzyme contains spatially distinct cyclooxygenase and peroxidase active sites, both of which require a heme cofactor. Substitution of ferric heme by Mn{sup III} protoporphyrin IX greatly diminishes the peroxidase activity, but has little effect on the cyclooxygenase activity. Here, the 2.0 Angstrom resolution crystal structure of the Mn{sup III} form of ovine prostaglandin H{sub 2} synthase-1 is described (R = 21.8%, R{sub free} = 23.7%). Substitution of Mn{sup III} for Fe{sup III} causes no structuralmore » perturbations in the protein. However, the out-of-plane displacement of the manganese ion with respect to the porphyrin is greater than that of the iron by approximately 0.2 Angstroms. This perturbation may help to explain the altered catalytic properties of the manganese enzyme.« less

  5. Porphyrin Cyclodextrin Conjugates Modulate Amyloid Beta Peptide Aggregation and Cytotoxicity.

    PubMed

    Oliveri, Valentina; Zimbone, Stefania; Giuffrida, Maria Laura; Bellia, Francesco; Tomasello, Marianna Flora; Vecchio, Graziella

    2018-04-25

    Although fibrillar amyloid beta peptide (Aβ) aggregates are one of the major hallmarks of Alzheimer's disease, increasing evidence suggests that soluble Aβ oligomers are the primary toxic species. Targeting the oligomeric species could represent an effective strategy to interfere with Aβ toxicity. In this work, the biological properties of 5[4-(6-O-β-cyclodextrin)-phenyl],10,15,20-tri(4-hydroxyphenyl)-porphyrin and its zinc complex were tested, as new molecules that interact with Aβ and effectively prevent its cytotoxicity. We found that these systems can cross the cell membrane to deliver Aβ intracellularly and promote its clearance. Our results provide evidence for the use of cyclodextrin-porphyrin derivatives as a promising strategy to target amyloid aggregation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Loss of halogens from crystallized and glassy silicic volcanic rocks

    USGS Publications Warehouse

    Noble, D.C.; Smith, V.C.; Peck, L.C.

    1967-01-01

    One hundred and sixty-four F and Cl analyses of silicic welded tuffs and lavas and glass separates are presented. Comparison of the F and Cl contents of crystallized rocks with those of nonhydrated glass and hydrated glassy rocks from the same rock units shows that most of the halogens originally present were lost on crystallization. An average of about half of the F and four-fifths of the Cl originally present was lost. Analyses of hydrated natural glasses and of glassy rocks indicate that in some cases significant amounts of halogens may be removed from or added to hydrated glass through prolonged contact with ground water. The data show that the original halogen contents of the groundmass of a silicic volcanic rock can be reliably determined only from nonhydrated glass. ?? 1967.

  7. Texaphyrins: Tumor Localizing Redox Active Expanded Porphyrins

    PubMed Central

    Arambula, Jonathan F.; Preihs, Christian; Borthwick, Derric; Magda, Darren; Sessler, Jonathan L.

    2011-01-01

    Texaphyrins, a class of tumor selective expanded porphyrins capable of coordinating large metals, have been found to act as redox mediators within biological systems. This review summarizes studies involving their experimentaluse in cancer chemotherapy. Mechanistic insights involving their presumed mode of action are also described, as well as certain structure activity relationships. Finally, newer texaphyrin-based applications associated with targeted drug delivery are presented. PMID:21355841

  8. A Survey of Electron Impact Cross-Sections for Halogens and Halogen Compounds of Interest to Plasma Processing

    NASA Technical Reports Server (NTRS)

    Sharma, S. P.; Rao, M. V. V. S.; Arnold, James O. (Technical Monitor)

    1998-01-01

    Published electron impact cross section data on halogens Cl2, F2, and halogen containing compounds such as Cx Fy, HCl, Cx Cly Fz are reviewed and critically evaluated based on the information provided by various researchers. The present work reports data on electron impact excitation, ionization, dissociation, electron attachment, electron detachment, and photo detachment. Elastic scattering cross sections and data on bulk properties such as diffusion coefficients in various background gases are also evaluated. Since some of the cross sectional data is derived from indirect measurements such as drift velocity, care has been taken to reconcile the differences among the reported data with due attention to the measurement technique. In conclusion, the processes with no or very limited amount of data and questionable set of data are identified and recommendation for further research direction is made.

  9. Do Halogen–Hydrogen Bond Donor Interactions Dominate the Favorable Contribution of Halogens to Ligand–Protein Binding?

    PubMed Central

    2017-01-01

    Halogens are present in a significant number of drugs, contributing favorably to ligand–protein binding. Currently, the contribution of halogens, most notably chlorine and bromine, is largely attributed to halogen bonds involving favorable interactions with hydrogen bond acceptors. However, we show that halogens acting as hydrogen bond acceptors potentially make a more favorable contribution to ligand binding than halogen bonds based on quantum mechanical calculations. In addition, bioinformatics analysis of ligand–protein crystal structures shows the presence of significant numbers of such interactions. It is shown that interactions between halogens and hydrogen bond donors (HBDs) are dominated by perpendicular C–X···HBD orientations. Notably, the orientation dependence of the halogen–HBD (X–HBD) interactions is minimal over greater than 100° with favorable interaction energies ranging from −2 to −14 kcal/mol. This contrasts halogen bonds in that X–HBD interactions are substantially more favorable, being comparable to canonical hydrogen bonds, with a smaller orientation dependence, such that they make significant, favorable contributions to ligand–protein binding and, therefore, should be actively considered during rational ligand design. PMID:28657759

  10. Halogen degassing during ascent and eruption of water-poor basaltic magma

    USGS Publications Warehouse

    Edmonds, M.; Gerlach, T.M.; Herd, Richard A.

    2009-01-01

    A study of volcanic gas composition and matrix glass volatile concentrations has allowed a model for halogen degassing to be formulated for K??lauea Volcano, Hawai'i. Volcanic gases emitted during 2004-2005 were characterised by a molar SO2/HCl of 10-64, with a mean of 33; and a molar HF/HCl of 0-5, with a mean of 1.0 (from approximately 2500 measurements). The HF/HCl ratio was more variable than the SO2/HCl ratio, and the two correlate weakly. Variations in ratio took place over rapid timescales (seconds). Matrix glasses of Pele's tears erupted in 2006 have a mean S, Cl and F content of 67, 85 and 173??ppm respectively, but are associated with a large range in S/F. A model is developed that describes the open system degassing of halogens from parental magmas, using the glass data from this study, previously published results and parameterisation of sulphur degassing from previous work. The results illustrate that halogen degassing takes place at pressures of < 1??MPa, equivalent to < ~ 35??m in the conduit. Fluid-melt partition coefficients for Cl and F are low (< 1.5); F only degasses appreciably at < 0.1??MPa above atmospheric pressure, virtually at the top of the magma column. This model reproduces the volcanic gas data and other observations of volcanic activity well and is consistent with other studies of halogen degassing from basaltic magmas. The model suggests that variation in volcanic gas halogen ratios is caused by exsolution and gas-melt separation at low pressures in the conduit. There is no evidence that either diffusive fractionation or near-vent chemical reactions involving halogens is important in the system, although these processes cannot be ruled out. The fluxes of HCl and HF from K??lauea during 2004-5 were ~ 25 and 12??t/d respectively. ?? 2008 Elsevier B.V.

  11. Estrogenicity of halogenated bisphenol A: in vitro and in silico investigations.

    PubMed

    Zhang, Jie; Li, Tiezhu; Wang, Tuoyi; Yuan, Cuiping; Zhong, Shuning; Guan, Tianzhu; Li, Zhuolin; Wang, Yongzhi; Yu, Hansong; Luo, Quan; Wang, Yongjun; Zhang, Tiehua

    2018-03-01

    The binding interactions of bisphenol A (BPA) and its halogenated derivatives (halogenated BPAs) to human estrogen receptor α ligand binding domain (hERα-LBD) was investigated using a combined in vitro and in silico approach. First, the recombinant hERα-LBD was prepared as a soluble protein in Escherichia coli BL21(DE3)pLysS. A native fluorescent phytoestrogen, coumestrol, was employed as tracer for the fluorescence polarization assay. The results of the in vitro binding assay showed that bisphenol compounds could bind to hERα-LBD as the affinity ligands. All the tested halogenated BPAs exhibited weaker receptor binding than BPA, which might be explained by the steric effect of substituents. Molecular docking studies elucidated that the halogenated BPAs adopted different conformations in the flexible hydrophobic ligand binding pocket (LBP), which is mainly dependent on their distinct halogenation patterns. The compounds with halogen substituents on the phenolic rings and on the bridging alkyl moiety acted as agonists and antagonists for hERα, respectively. Interestingly, all the compounds in the agonist conformation of hERα formed a hydrogen bond with His524, while the compounds in the antagonist conformation formed a hydrogen bond with Thr347. These docking results suggested a pivotal role of His524/Thr347 in maintaining the hERα structure in the biologically active agonist/antagonist conformation. Comparison of the calculated binding energies vs. experimental binding affinities yielded a good correlation, which might be applicable for the structure-based design of novel bisphenol compounds with reduced toxicities and for environmental risk assessment. In addition, based on hERα-LBD as a recognition element, the proposed fluorescence polarization assay may offer an alternative to chromatographic techniques for the multi-residue determination of bisphenol compounds.

  12. Controlled intracellular generation of reactive oxygen species in human mesenchymal stem cells using porphyrin conjugated nanoparticles

    NASA Astrophysics Data System (ADS)

    Lavado, Andrea S.; Chauhan, Veeren M.; Alhaj Zen, Amer; Giuntini, Francesca; Jones, D. Rhodri E.; Boyle, Ross W.; Beeby, Andrew; Chan, Weng C.; Aylott, Jonathan W.

    2015-08-01

    Nanoparticles capable of generating controlled amounts of intracellular reactive oxygen species (ROS), that advance the study of oxidative stress and cellular communication, were synthesized by functionalizing polyacrylamide nanoparticles with zinc(ii) porphyrin photosensitisers. Controlled ROS production was demonstrated in human mesenchymal stem cells (hMSCs) through (1) production of nanoparticles functionalized with varying percentages of Zn(ii) porphyrin and (2) modulating the number of doses of excitation light to internalized nanoparticles. hMSCs challenged with nanoparticles functionalized with increasing percentages of Zn(ii) porphyrin and high numbers of irradiations of excitation light were found to generate greater amounts of ROS. A novel dye, which is transformed into fluorescent 7-hydroxy-4-trifluoromethyl-coumarin in the presence of hydrogen peroxide, provided an indirect indicator for cumulative ROS production. The mitochondrial membrane potential was monitored to investigate the destructive effect of increased intracellular ROS production. Flow cytometric analysis of nanoparticle treated hMSCs suggested irradiation with excitation light signalled controlled apoptotic cell death, rather than uncontrolled necrotic cell death. Increased intracellular ROS production did not induce phenotypic changes in hMSC subcultures.Nanoparticles capable of generating controlled amounts of intracellular reactive oxygen species (ROS), that advance the study of oxidative stress and cellular communication, were synthesized by functionalizing polyacrylamide nanoparticles with zinc(ii) porphyrin photosensitisers. Controlled ROS production was demonstrated in human mesenchymal stem cells (hMSCs) through (1) production of nanoparticles functionalized with varying percentages of Zn(ii) porphyrin and (2) modulating the number of doses of excitation light to internalized nanoparticles. hMSCs challenged with nanoparticles functionalized with increasing percentages of Zn

  13. Evaluating the potential for halogen bonding in ketosteroid isomerase’s oxyanion hole using unnatural amino acid mutagenesis

    PubMed Central

    Kraut, Daniel A; Churchil, Michael J; Dawson, Phillip E

    2009-01-01

    There has recently been an increasing interest in controlling macromolecular conformations and interactions through halogen bonding. Halogen bonds are favorable electrostatic interactions between polarized, electropositive chlorine, bromine or iodine atoms and electronegative atoms such as oxygen or nitrogen. These interactions have been likened to hydrogen bonds both in terms of their favored acceptor molecules, their geometries, and their energetics. We asked whether a halogen bond could replace a hydrogen bond in the oxyanion hole of ketosteroid isomerase, using semi-synthetic enzyme containing para-halogenated phenylalanine derivatives to replace the tyrosine hydrogen bond donor. Formation of a halogen bond to the oxyanion in the transition state would be expected to rescue the effects of mutation to phenylalanine, but all of the halogenated enzymes were comparable in activity to the phenylalanine mutant. We conclude that, at least in this active site, a halogen bond cannot functionally replace a hydrogen bond. PMID:19260691

  14. Synthesis and photophysical properties of halogenated derivatives of (dibenzoylmethanato)boron difluoride

    NASA Astrophysics Data System (ADS)

    Kononevich, Yuriy N.; Surin, Nikolay M.; Sazhnikov, Viacheslav A.; Svidchenko, Evgeniya A.; Aristarkhov, Vladimir M.; Safonov, Andrei A.; Bagaturyants, Alexander A.; Alfimov, Mikhail V.; Muzafarov, Aziz M.

    2017-03-01

    A series of (dibenzoylmethanato)boron difluoride (BF2DBM) derivatives with a halogen atom in one of the phenyl rings at the para-position were synthesized and used to elucidate the effects of changing the attached halogen atom on the photophysical properties of BF2DBM. The room-temperature absorption and fluorescence maxima of fluoro-, chloro-, bromo- and iodo-substituted derivatives of BF2DBM in THF are red-shifted by about 2-10 nm relative to the corresponding peaks of the parent BF2DBM. The fluorescence quantum yields of the halogenated BF2DBMs (except the iodinated derivative) are larger than that of the unsubstituted BF2DBM. All the synthesized compounds are able to form fluorescent exciplexes with benzene and toluene (emission maxima at λem = 433 and 445 nm, respectively). The conformational structure and electronic spectral properties of halogenated BF2DBMs have been modeled by DFT/TDDFT calculations at the PBE0/SVP level of theory. The structure and fluorescence spectra of exciplexes were calculated using the CIS method with empirical dispersion correction.

  15. Radiosynthesis and Quality Control of [67Ga]-3,4-dimethoxylated Porphyrin Complex as a Possible Imaging agent

    PubMed Central

    Paknafas, Azadeh; Fazaeli, Yousef; Jalilian, Amir Reza; Ahmadi, Abbas; Feizi, Shahzad; Kamalidehghan, Mohsen; Rahiminejad, Ali; Khalaj, Ali

    2013-01-01

    Radiolabeled porphyrins are potential tumor avid radiopharmaceuticals because of their impersonation in the human body, ability to complex various radionuclides, water solubility, low toxicity etc. In this work a radiogallium porphyrin complex has been developed. [67Ga] labeled 5,10,15,20-tetrakis(3,4-dimethoxyphenyl) porphyrin ([67Ga]-TDMPP) was prepared using freshly prepared [67Ga]GaCl3 and 5,10,15,20-tetrakis(3,4-dimethoxyphenyl) porphyrin (H2TDMPP) for 60 min at 100°C. Stability of the complex was checked in final formulation and human serum for 24 h, followed by biodistribution and imaging studies in wild type rats up to 24 h. The radiocomplex was obtained with radiochemical purity >99% (ITLC) and >98% (HPLC), specific activity: 12-15 GBq/mmol. The partition coefficient was determined (log P=1.63). A detailed comparative pharmacokinetic study performed for 67Ga cation and [67Ga]-TDMPP. The complex was mostly washed out from the circulation through kidneys. Myocardial uptake was significantly observed by SPECT and biodistribution studies. Knee and shoulder joints demonstrated significant activity uptake in 2h post injection. Higher water solubility of the complex due to ionic nature of the complex is an advantage for rapid wash-out of the complex from the system, the complex has significant joint uptake compared to other radiolabeled porphyrins which the mechanisms are explained. PMID:24523753

  16. Sequential energy and charge transfer processes in mixed host-guest complexes of subphthalocyanine, porphyrin and phthalocyanine chromophores.

    PubMed

    Menting, Roel; Ng, Dennis K P; Röder, Beate; Ermilov, Eugeny A

    2012-11-14

    Porphyrins, phthalocyanines and subphthalocyanines are three attractive classes of chromophores with intriguing properties making them suitable for the design of artificial photosynthetic systems. The assembly of these components by a supramolecular approach is of particular interest as it provides a facile means to build multi-chromophoric arrays with various architectures and tuneable photophysical properties. In this paper, we show the formation of mixed host-guest supramolecular complexes that consist of a β-cyclodextrin-conjugated subphthalocyanine, a tetrasulfonated porphyrin and a series of silicon(IV) phthalocyanines substituted axially with two β-cyclodextrins via different spacers. We found that the three components form supramolecular complexes held by host-guest interactions in aqueous solution. Upon excitation of the subphthalocyanine part of the complex, the excitation energy is delivered to the phthalocyanine unit via excitation energy transfer and the porphyrin chromophore acts as an energy transfer bridge enabling this process. It was shown that photo-induced charge transfer also takes place. A sequential electron transfer process from the porphyrin unit to the phthalocyanine moiety and subsequently from the subphthalocyanine moiety to the porphyrin unit takes place, and the probability of this process is controlled by the linker between β-cyclodextrin and phthalocyanine. The lifetime of the charge-separated state was found to be 1.7 ns by transient absorption spectroscopy.

  17. Synthesis, characterization, and nonlinear optical properties of graphene oxide functionalized with tetra-amino porphyrin

    NASA Astrophysics Data System (ADS)

    Yamuna, R.; Ramakrishnan, S.; Dhara, Keerthy; Devi, R.; Kothurkar, Nikhil K.; Kirubha, E.; Palanisamy, P. K.

    2013-01-01

    The synthesis of a porphyrin-graphene oxide hybrid (GO-TAP) was carried out by covalently functionalizing graphene oxide (GO) with 5,10,15,20 mesotetra (4-aminophenyl) porphyrin (TAP) through an amide linkage. The GO-TAP hybrid has been characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and UV-visible spectroscopy. The peak intensity of the Soret band of the material was suppressed compared to neat TAP. This indicates a strong interaction between the electronic energy level of TAP and GO in the GO-TAP hybrid. The functionalization of GO with TAP significantly improved its solubility and dispersion stability in organic solvents. Scanning electron micrographs reveal that the hybrid was found to be similar to the unmodified GO but slightly more wrinkled. Transmission electron micrographs also demonstrate that GO sheet in the hybrid is more wrinkled with some dark spot due to functionalization. Atomic force microscopy results also reveal that the TAP functionalization increases the thickness of GO sheet to 2.0-3.0 nm from 1.2 to 1.8 nm. We observed improved nonlinear optical and optical limiting properties for the hybrid compared to both graphene oxide and porphyrin. GO-TAP shows fluorescence quenching compared with porphyrin, indicating excellent electron and/or energy transfer to GO from TAP. Thermogravimetric analysis confirms that the GO-TAP hybrid has outstanding thermal stability.

  18. Broad hexagonal columnar mesophases formation in bioinspired transition-metal complexes of simple fatty acid meta-octaester derivatives of meso-tetraphenyl porphyrins.

    PubMed

    Wu, Bin; Chen, Keyang; Deng, Yuchen; Chen, Jian; Liu, Chengjie; Cheng, Rongshi; Chen, Dongzhong

    2015-02-23

    A series of meta-substituted fatty acid octaester derivatives and their transition-metal complexes of meso- tetraphenyl porphyrins (TPP-8OOCR, with R = C(n-1)H(2n-1), n = 8, 12, or 16) have been prepared through very simple synthesis protocols. The thermotropic phase behavior and the liquid crystalline (LC) organization structures of the synthesized porphyrin derivatives were systematically investigated by a combination of differential scanning calorimetry (DSC), polarized optical microscopy (POM), and variable-temperature small-angle X-ray scattering/wide-angle X-ray scattering (SAXS/WAXS) techniques. The shorter octanoic acid ester substituted porphyrin (C8-TPP) did not show liquid crystallinity and its metal porphyrins exhibited an uncommon columnar mesophase. The lauric acid octaester (C12-TPP) and the palmitic acid octaester (C16-TPP) series porphyrins generated hexagonal columnar mesophase Colh. Moreover, the metal porphyrins C12-TPPM and C16-TPPM with M = Zn, Cu, or Ni, exhibited well-organized Colh mesophases of broad LC temperature ranges increasing in the order of TPPNiporphyrins and their metal complexes very attractive for variant applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Porphyrin-laser photodynamic induction of focal brain necrosis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Stroop, W.G.; Battles, E.J.; Townsend, J.J.

    A noninvasive photodynamic method has been developed to produce focal brain necrosis using porphyrin activated in vivo with laser light. After peripheral injection of the photosensitive porphyrin derivative, Photofrin I, mice were irradiated on the posterior lateral aspect of the head through the intact depilated scalp with 632 nm argon-dye laser light. Animals were studied at one, two and seven days after irradiation. Blood-brain barrier damage was detected by the intravenous injection of Evans blue, horseradish peroxidase and heterologous immunoglobulins. At one and two days after irradiation, the lesions were characterized by extravasation of immunoglobulin and Evans blue, and bymore » edema, ischemia and infiltration by monocytes. On the seventh day after irradiation, the lesion was smaller than it had been two days after irradiation, and had reactive changes at its edges and coagulative necrosis at its center. Extravasation of Evans blue and immunoglobulin was markedly reduced by the seventh day after irradiation, but uptake of horseradish peroxidase by macrophages located at the periphery of the lesion was evident.« less

  20. Direct nitration and azidation of aliphatic carbons by an iron-dependent halogenase

    PubMed Central

    Chang, Wei-chen; Layne, Andrew P; Miles, Linde A; Krebs, Carsten

    2014-01-01

    Iron-dependent halogenases employ cis-halo-Fe(IV)-oxo (haloferryl) complexes to functionalize unactivated aliphatic carbon centers, a capability elusive to synthetic chemists. Halogenation requires (1) coordination of a halide anion (Cl− or Br−) to the enzyme's Fe(II) cofactor; (2) coupled activation of O2 and decarboxylation of α-ketoglutarate to generate the haloferryl intermediate; (3) abstraction of hydrogen (H•) from the substrate by the ferryl oxo group; and (4) transfer of the cis halogen as Cl• or Br• to the substrate radical. This enzymatic solution to an unsolved chemical challenge is potentially generalizable to installation of other functional groups, provided that the corresponding anions can support the four requisite steps. We show here that the wild-type halogenase SyrB2 can indeed direct aliphatic nitration and azidation reactions by the same chemical logic. The discovery and enhancement by mutagenesis of these previously unknown reaction types suggests unrecognized or untapped versatility in ferryl-mediated enzymatic C–H-bond activation. PMID:24463698

  1. Spontaneous Tl(I)-to-Tl(III) oxidation in dynamic heterobimetallic Hg(II)/Tl(I) porphyrin complexes.

    PubMed

    Ndoyom, Victoria; Fusaro, Luca; Roisnel, Thierry; Le Gac, Stéphane; Boitrel, Bernard

    2016-01-11

    Strapped heterobimetallic Hg(II)/Tl(I) porphyrin complexes, with both metal ions bridged by the N-core in a dynamic way, undergo spontaneous Tl(I)-to-Tl(III) oxidation leading to a mono-Tl(III) complex and a mixed valence Tl(I)/Tl(III) bimetallic complex. It provides a new opportunity to tune metal ion translocations in bimetallic porphyrin systems.

  2. Porphyrin-containing polyaspartamide gadolinium complexes as potential magnetic resonance imaging contrast agents.

    PubMed

    Yan, Guo-Ping; Li, Zhen; Xu, Wei; Zhou, Cheng-Kai; Yang, Lian; Zhang, Qiao; Li, Liang; Liu, Fan; Han, Lin; Ge, Yuan-Xing; Guo, Jun-Fang

    2011-04-04

    Porphyrin-containing polyaspartamide ligands (APTSPP-PHEA-DTPA) were synthesized by the incorporation of diethylenetriaminepentaacetic acid (DTPA) and 5-(4'-aminophenyl)-10,15,20-tris(4'-sulfonatophenyl) porphyrin, trisodium salt (APTSPP) into poly-α,β-[N-(2-hydroxyethyl)-l-aspartamide] (PHEA). These ligands were further reacted with gadolinium chloride to produce macromolecule-gadolinium complexes (APTSPP-PHEA-DTPA-Gd). Experimental data of (1)H NMR, IR, UV and elemental analysis evidenced the formation of the polyaspartamide ligands and gadolinium complexes. In vitro and in vivo property tests indicated that APTSPP-PHEA-DTPA-Gd possessed noticeably higher relaxation effectiveness, less toxicity to HeLa cells, and significantly higher enhanced signal intensities (SI) of the VX2 carcinoma in rabbits with lower injection dose requirement than that of Gd-DTPA. Moreover, APTSPP-PHEA-DTPA-Gd was found to greatly enhance the contrast of MR images of the VX2 carcinoma, providing prolonged intravascular duration, and distinguished the VX2 carcinoma and normal tissues in rabbits according to MR image signal enhancements. These porphyrin-containing polyaspartamide gadolinium complexes can be used as the candidates of contrast agents for targeted MRI to tumors. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

  3. A Review of Hydrogen/Halogen Flow Cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cho, Kyu Taek; Tucker, Michael C.; Weber, Adam Z.

    Flow batteries provide an energy-storage solution for various grid-related stability and service issues that arise as renewable-energy-generation technologies are adopted. Among the most promising flow-battery systems are those using hydrogen/halogen redox couples, which promise the possibility of meeting the cost target of the US Department of Energy (DOE), due to their fast and reversible kinetics and low materials cost. However, significant critical issues and barriers for their adoption remain. In this review of halogen/hydrogen systems, technical and performance issues, and research and development progress are reviewed. The information in this review can be used as a technical guide for researchmore » and development of related redox-flow-battery systems and other electrochemical technologies.« less

  4. Method and apparatus for detecting halogenated hydrocarbons

    DOEpatents

    Monagle, Matthew; Coogan, John J.

    1997-01-01

    A halogenated hydrocarbon (HHC) detector is formed from a silent discharge (also called a dielectric barrier discharge) plasma generator. A silent discharge plasma device receives a gas sample that may contain one or more HHCs and produces free radicals and excited electrons for oxidizing the HHCs in the gas sample to produce water, carbon dioxide, and an acid including halogens in the HHCs. A detector is used to sensitively detect the presence of the acid. A conductivity cell detector combines the oxidation products with a solvent where dissociation of the acid increases the conductivity of the solvent. The conductivity cell output signal is then functionally related to the presence of HHCs in the gas sample. Other detectors include electrochemical cells, infrared spectrometers, and negative ion mobility spectrometers.

  5. A Review of Hydrogen/Halogen Flow Cells

    DOE PAGES

    Cho, Kyu Taek; Tucker, Michael C.; Weber, Adam Z.

    2016-05-17

    Flow batteries provide an energy-storage solution for various grid-related stability and service issues that arise as renewable-energy-generation technologies are adopted. Among the most promising flow-battery systems are those using hydrogen/halogen redox couples, which promise the possibility of meeting the cost target of the US Department of Energy (DOE), due to their fast and reversible kinetics and low materials cost. However, significant critical issues and barriers for their adoption remain. In this review of halogen/hydrogen systems, technical and performance issues, and research and development progress are reviewed. The information in this review can be used as a technical guide for researchmore » and development of related redox-flow-battery systems and other electrochemical technologies.« less

  6. Halogens, Barium and Uranium in Mantle Fluid Inclusions

    NASA Astrophysics Data System (ADS)

    Villa, I. M.; Peverelli, V.; Oglialoro, E.; Pettke, D. T.; Frezzotti, M. L.

    2016-12-01

    Halogens are an underexplored geochemical marker. A way to measure halogens at ng/g levels is measuring Ar, Kr and Xe in irradiated samples [1,2]. We derive absolute halogen amounts from rare gas amounts via scapolite monitor SY [2]. Kr-Xe systematics also yield Ba and U concentrations. We combined irradiation with stepheating on carbonate-sulfate-rich fluid inclusions (FI)-bearing xe­no­liths from El Hierro, Canarias: spinel harzburgite XML-7 and spinel dunite XML-1 [3]. Three components are recognized in the rare gas release. (1) Atmospheric surface contamination occurs up to 1000 °C. (2) FI decrepitation by laboratory heating occurs above 1200 °C [4], corresponding to the release of 80,82Kr and 128Xe in the 1200 and 1400 °C steps. Br whole-rock concentrations are 3-8 ng/g; the molar Br/Cl and I/Cl ratios in the harzburgite FI, 9 E-4 resp. 2 E-4, are identical to those in the dunite FI. This sets the halogens in our FI apart from MORB [2]. Halogen-derived rare gases are closely associated to artificial 131Xe from Ba; Ba has a high affinity of for CO2-rich fluids. Daughter minerals in multiphase FI were identified by Raman micro­spectroscopy [4]. The calculated Ba concentrations are 2-6 µg/g. (3) The third component is U-derived 134,136Xe and 86Kr released in a spike at 1000 °C, decoupled from FI. This requires a different carrier than FI, e.g. Ti oxides. As U concentrations are 10-20 pg/g, the U-bearing phase needs to be below a ppm, invisible by petro­graphy. The 136Xe/134Xe ratio > 1 suggests retention of radio­genic Xe. However, analysis of an unirradiated sample detected no radiogenic Xe. It is likely that Xe-U produced in the core of the McMaster reactor (thermal, epithermal and fast neutrons) has a different isotopic composition from that in textbooks, as proposed by [2].[1] Jeffery & Reynolds (1961) J.Geophys. Res. 66, 3582 [2] Kendrick (2012) Chem. Geol. 292, 116 [3] Oglialoro et al (2015) AGU Fall Meeting abstract V21C-3046 [4] Roedder (1965

  7. Process for removing halogenated aliphatic and aromatic compounds from petroleum products

    DOEpatents

    Googin, J.M.; Napier, J.M.; Travaglini, M.A.

    1983-09-20

    A process is described for removing halogenated aliphatic and aromatic compounds, e.g., polychlorinated biphenyls, from petroleum products by solvent extraction. The halogenated aliphatic and aromatic compounds are extracted from a petroleum product into a polar solvent by contacting the petroleum product with the polar solvent. The polar solvent is characterized by a high solubility for the extracted halogenated aliphatic and aromatic compounds, a low solubility for the petroleum product and considerable solvent power for polyhydroxy compound. The preferred polar solvent is dimethylformamide. A miscible compound, such as, water or a polyhydroxy compound, is added to the polar extraction solvent to increase the polarity of the polar extraction solvent. The halogenated aliphatic and aromatic compounds are extracted from the highly-polarized mixture of water or polyhydroxy compound and polar extraction solvent into a low polar or nonpolar solvent by contacting the water or polyhydroxy compound-polar solvent mixture with the low polar or nonpolar solvent. The halogenated aliphatic and aromatic compounds and the low polar or nonpolar solvent are separated by physical means, e.g., vacuum evaporation. The polar and nonpolar solvents are recovered from recycling. The process can easily be designed for continuous operation. Advantages of the process include that the polar solvent and a major portion of the nonpolar solvent can be recycled, the petroleum products are reclaimable and the cost for disposing of waste containing polychlorinated biphenyls is significantly reduced. 1 fig.

  8. 79/81Br nuclear quadrupole resonance spectroscopic characterization of halogen bonds in supramolecular assemblies.

    PubMed

    Cerreia Vioglio, P; Szell, P M J; Chierotti, M R; Gobetto, R; Bryce, D L

    2018-05-28

    Despite the applicability of solid-state NMR to study the halogen bond, the direct NMR detection of 79/81 Br covalently bonded to carbon remains impractical due to extremely large spectral widths, even at ultra-high magnetic fields. In contrast, nuclear quadrupole resonance (NQR) offers comparatively sharp resonances. Here, we demonstrate the abilities of 79/81 Br NQR to characterize the electronic changes in the C-Br···N halogen bonding motifs found in supramolecular assemblies constructed from 1,4-dibromotetrafluorobenzene and nitrogen-containing heterocycles. An increase in the bromine quadrupolar coupling constant is observed, which correlates linearly with the halogen bond distance ( d Br···N ). Notably, 79/81 Br NQR is able to distinguish between two symmetry-independent halogen bonds in the same crystal structure. This approach offers a rapid and reliable indication for the occurrence of a halogen bond, with experimental times limited only by the observation of 79/81 Br NQR resonances.

  9. Spectroscopic studies on the interaction of a water-soluble cationic porphyrin with proteins.

    PubMed

    Ma, Hong-Min; Chen, Xin; Zhang, Nuo; Han, Yan-Yan; Wu, Dan; Du, Bin; Wei, Qin

    2009-04-01

    The interaction of a water-soluble cationic porphyrin, meso-tetrakis (4-N,N,N-trimethylanilinium) porphyrin (TMAP), with two proteins, bovine serum albumin (BSA) and human serum albumin (HSA), was studied by UV-vis absorption spectroscopy, fluorescence spectroscopy, fluorescence anisotropy and synchronous fluorescence spectroscopy at neutral aqueous solutions. Free base TMAP bound to proteins as monomers and no aggregation was observed. The binding of TMAP quenched the fluorescence of the protein. On the contrary, the fluorescence of TMAP was enhanced and the fluorescence anisotropy increased due to the binding. The direct static binding mechanism could account for the quenching by TMAP and the binding constants were calculated. TMAP showed a higher quenching efficiency and binding constant of HSA than BSA. The binding of TMAP had no obvious effect on the molecular conformation of the protein. There was only one binding site for TMAP and it was located on the surface of the protein molecule. Electrostatic force played an important role in the binding due to the opposite charges on porphyrin and the proteins.

  10. Spectroscopic studies on the interaction of a water-soluble cationic porphyrin with proteins

    NASA Astrophysics Data System (ADS)

    Ma, Hong-Min; Chen, Xin; Zhang, Nuo; Han, Yan-Yan; Wu, Dan; Du, Bin; Wei, Qin

    2009-04-01

    The interaction of a water-soluble cationic porphyrin, meso-tetrakis (4- N, N, N-trimethylanilinium) porphyrin (TMAP), with two proteins, bovine serum albumin (BSA) and human serum albumin (HSA), was studied by UV-vis absorption spectroscopy, fluorescence spectroscopy, fluorescence anisotropy and synchronous fluorescence spectroscopy at neutral aqueous solutions. Free base TMAP bound to proteins as monomers and no aggregation was observed. The binding of TMAP quenched the fluorescence of the protein. On the contrary, the fluorescence of TMAP was enhanced and the fluorescence anisotropy increased due to the binding. The direct static binding mechanism could account for the quenching by TMAP and the binding constants were calculated. TMAP showed a higher quenching efficiency and binding constant of HSA than BSA. The binding of TMAP had no obvious effect on the molecular conformation of the protein. There was only one binding site for TMAP and it was located on the surface of the protein molecule. Electrostatic force played an important role in the binding due to the opposite charges on porphyrin and the proteins.

  11. Metal-porphyrin: a potential catalyst for direct decomposition of N(2)O by theoretical reaction mechanism investigation.

    PubMed

    Maitarad, Phornphimon; Namuangruk, Supawadee; Zhang, Dengsong; Shi, Liyi; Li, Hongrui; Huang, Lei; Boekfa, Bundet; Ehara, Masahiro

    2014-06-17

    The adsorption of nitrous oxide (N2O) on metal-porphyrins (metal: Ti, Cr, Fe, Co, Ni, Cu, or Zn) has been theoretically investigated using density functional theory with the M06L functional to explore their use as potential catalysts for the direct decomposition of N2O. Among these metal-porphyrins, Ti-porphyrin is the most active for N2O adsorption in the triplet ground state with the strongest adsorption energy (-13.32 kcal/mol). Ti-porphyrin was then assessed for the direct decomposition of N2O. For the overall reaction mechanism of three N2O molecules on Ti-porphyrin, two plausible catalytic cycles are proposed. Cycle 1 involves the consecutive decomposition of the first two N2O molecules, while cycle 2 is the decomposition of the third N2O molecule. For cycle 1, the activation energies of the first and second N2O decompositions are computed to be 3.77 and 49.99 kcal/mol, respectively. The activation energy for the third N2O decomposition in cycle 2 is 47.79 kcal/mol, which is slightly lower than that of the second activation energy of the first cycle. O2 molecules are released in cycles 1 and 2 as the products of the reaction, which requires endothermic energies of 102.96 and 3.63 kcal/mol, respectively. Therefore, the O2 desorption is mainly released in catalytic cycle 2 of a TiO3-porphyrin intermediate catalyst. In conclusion, regarding the O2 desorption step for the direct decomposition of N2O, the findings would be very useful to guide the search for potential N2O decomposition catalysts in new directions.

  12. High-Potential Porphyrins Supported on SnO 2 and TiO 2 Surfaces for Photoelectrochemical Applications

    DOE PAGES

    Jiang, Jianbing; Swierk, John R.; Materna, Kelly L.; ...

    2016-12-03

    Here, we report CF 3-substituted porphyrins and evaluate their use as photosensitizers in water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) by characterizing interfacial electron transfer on metal oxide surfaces. Furthermore, by using (CF 3) 2C 6H 3 instead of C 6F 5 substituents at the meso positions, we obtain the desired high potentials while avoiding the sensitivity of C 6F 5 substituents to nucleophilic substitution, a process that limits the types of synthetic reactions that can be used. Both the number of CF 3 groups and the central metal tune the ground and excited-state potentials. A pair of porphyrins bearing carboxylic acidsmore » as anchoring groups were deposited on SnO 2 and TiO 2 surfaces and the interfacial charge-injection and charge-recombination kinetics were characterized by using a combination of computational modeling, terahertz measurements, and transient absorption spectroscopy. We also found that both free-base and metallated porphyrins inject into SnO 2, and that recombination is slower for the latter case. Our findings demonstrate that (CF 3) 2C 6H 3-substituted porphyrins are promising photosensitizers for use in WS-DSPECs.« less

  13. Giant Stark effect in double-stranded porphyrin ladder polymers

    NASA Astrophysics Data System (ADS)

    Pramanik, Anup; Kang, Hong Seok

    2011-03-01

    Using the first-principles calculations, we have investigated the stability and the electronic structure of two types of recently synthesized one-dimensional nanoribbons, i.e., double-stranded zinc(II) porphyrin ladder polymer (LADDER) arrays. First, electronic structure calculations were used to show that the LADDER is a semiconductor. Most importantly, the application of a transverse electric field significantly reduces the band gap of the LADDER, ultimately converting the LADDER to a metal at a field strength of 0.1 V/Å. The giant Stark effect in this case is almost as strong as that in boron nitride nanotubes and nanoribbons. In the presence of an electric field, hole conduction and electronic conduction will occur entirely through spatially separated strands, rendering these materials useful for nanoelectronic devices. Second, the substitution of hydrogen atoms in the porphyrin units or that of zinc ions with other kinds of chemical species is found to increase the binding strength of the LADDER and reduce the band gap.

  14. Modulation of the fibrillogenesis inhibition properties of two transthyretin ligands by halogenation.

    PubMed

    Cotrina, Ellen Y; Pinto, Marta; Bosch, Lluís; Vilà, Marta; Blasi, Daniel; Quintana, Jordi; Centeno, Nuria B; Arsequell, Gemma; Planas, Antoni; Valencia, Gregorio

    2013-11-27

    The amyloidogenic protein transthyretin (TTR) is thought to aggregate into amyloid fibrils by tetramer dissociation which can be inhibited by a number of small molecule compounds. Our analysis of a series of crystallographic protein-inhibitor complexes has shown no clear correlation between the observed molecular interactions and the in vitro activity of the inhibitors. From this analysis, it emerged that halogen bonding (XB) could be mediating some key interactions. Analysis of the halogenated derivatives of two well-known TTR inhibitors has shown that while flufenamic acid affinity for TTR was unchanged by halogenation, diflunisal gradually improves binding up to 1 order of magnitude after iodination through interactions that can be interpreted as a suboptimal XB (carbonyl Thr106: I...O distance 3.96-4.05 Å; C-I...O angle 152-156°) or as rather optimized van der Waals contacts or as a mixture of both. These results illustrate the potential of halogenation strategies in designing and optimizing TTR fibrillogenesis inhibitors.

  15. HepG2 human hepatocarcinomas cells sensitization by endogenous porphyrins

    NASA Astrophysics Data System (ADS)

    Vonarx-Coinsmann, Veronique; Foultier, Marie-Therese; de Brito, Leonor X.; Morlet, Laurent; Patrice, Thierry

    1995-03-01

    We assessed the ability of the human hepatocarcinoma cell line HepG2 to synthesize PpIX in vitro from exogenous ALA and analyzed ALA-induced toxicity and phototoxicity on this cell line. ALA induced a slight dose-dependent dark toxicity, with 79 and 66% cell survival respectively for ALA 50 and 100 mg/ml after 3-h incubation. Whereas the same treatment followed by laser irradiation (l equals 632 nm, 25 J/sq cm) induced dose-dependent phototoxicity, with 54 and 19% cell survival 24 h after PDT. Whatever the incubation time with ALA, a 3-h delay before light exposure was found optimal to reach a maximal phototoxicity. Photoproducts induced by porphyrin light irradiation absorbed light in the red spectral region at longer wavelengths than did the original porphyrins. The possible enhancement of PDT effects after ALA HepG2 cell incubation was investigated by irradiating cells successively with red light (l equals 632 nm) and light (l equals 650 nm). Total fluence was kept constant at 25 J/sq cm. Phototoxicity was lower when cells were irradiated for increased periods of l equals 650 nm light than with l equals 632 nm light alone. Any photoproducts involved had either a short life or were poorly photoreactive. HepG2 cells, synthesizing enzymes and precursors of endogenous porphyrin synthesis, represent a good in vitro model for experiments using ALA-PpIX-PDT.

  16. Photophysical study of meso-phenothiazinyl-porphyrins metallocomplexes

    NASA Astrophysics Data System (ADS)

    Starukhin, Aleksander; Gorski, Aleksander; Knyukshto, Valery; Panarin, Andrei; Pavich, Tatiana; Gaina, Luiza; Gal, Emese

    2017-10-01

    Photophysical parameters of a set of metallocomplexes of meso-phenylthiazinylporphyrins with Zn (II), Pd (II) and Cu (II) ions were studied in different organic solvents, solid solutions and polymeric matrices at room and liquid nitrogen temperatures. The dependence of the spectral and photophysical parameters on changing the molecular structure with increasing number of branched substituents attached to aryl groups in different positions of the porphyrin macrocycle has been established.

  17. The Conductance of Porphyrin-Based Molecular Nanowires Increases with Length.

    PubMed

    Algethami, Norah; Sadeghi, Hatef; Sangtarash, Sara; Lambert, Colin J

    2018-06-13

    High electrical conductance molecular nanowires are highly desirable components for future molecular-scale circuitry, but typically molecular wires act as tunnel barriers and their conductance decays exponentially with length. Here, we demonstrate that the conductance of fused-oligo-porphyrin nanowires can be either length independent or increase with length at room temperature. We show that this negative attenuation is an intrinsic property of fused-oligo-porphyrin nanowires, but its manifestation depends on the electrode material or anchor groups. This highly desirable, nonclassical behavior signals the quantum nature of transport through such wires. It arises because with increasing length the tendency for electrical conductance to decay is compensated by a decrease in their highest occupied molecular orbital-lowest unoccupied molecular orbital gap. Our study reveals the potential of these molecular wires as interconnects in future molecular-scale circuitry.

  18. Porphyrin-sensitized solar cells: systematic molecular optimization, coadsorption and cosensitization.

    PubMed

    Song, Heli; Liu, Qingyun; Xie, Yongshu

    2018-02-15

    As a promising low-cost solar energy conversion technique, dye-sensitized solar cells have undergone spectacular development since 1991. For practical applications, improvement of power conversion efficiency has always been one of the major research topics. Porphyrins are outstanding sensitizers endowed with strong sunlight harvesting ability in the visible region and multiple reaction sites available for functionalization. However, judicious molecular design in consideration of light-harvest, energy levels, operational dynamics, adsorption geometry and suppression of back reactions is specifically required for achieving excellent photovoltaic performance. This feature article highlights some of the recently developed porphyrin sensitizers, especially focusing on the systematic dye structure optimization approach in combination with coadsorption and cosensitization methods in pursuing higher efficiencies. Herein, we expect to provide more insights into the structure-performance correlation and molecular engineering strategies in a stepwise manner.

  19. Partial separation of halogens during the subduction of oceanic crust

    NASA Astrophysics Data System (ADS)

    Joachim, Bastian; Pawley, Alison; Lyon, Ian; Henkel, Torsten; Clay, Patricia L.; Ruzié, Lorraine; Burgess, Ray; Ballentine, Christopher J.

    2014-05-01

    Incompatible elements, such as halogens, have the potential to act as key tracers for volatile transport processes in Earth and planetary systems. The determination of halogen abundances and ratios in different mantle reservoirs gives us the ability to better understand volatile input mechanisms into the Earth's mantle through subduction of oceanic crust. Halogen partition coefficients were experimentally determined between forsterite, orthopyroxene and silicate melt at pressures ranging from 1.0 to 2.3 GPa and temperatures ranging from 1500-1600°C, thus representing partial melting conditions of the Earth's mantle. Combining our data with results of recent studies (Beyer et al. 2012; Dalou et al. 2012) shows that halogen partitioning between forsterite and melt increases by factors of about 1000 (fluorine) and 100 (chlorine) between 1300°C and 1600°C and does not show any pressure dependence. Chlorine partitioning between orthopyroxene and melt increases by a factor of about 1500 for a temperature increase of 100°C (anywhere between 1300°C and 1600°C), but decreases by a factor of about 1500 for a pressure increase of 1.0 GPa (anywhere between 1.0 GPa and 2.5 GPa). At similar P-T conditions, a comparable effect is observed for the fluorine partitioning behaviour, which increases by 500-fold for a temperature increase of 100°C and decreases with increasing pressure. Halogen abundances in mid-ocean ridge basalts (MORB; F=3-15, Cl=0.5-14ppm) and ocean island basalts (OIB; F=35-65, Cl=21-55 ppm) source regions were estimated by combining our experimentally determined partition coefficients with natural halogen concentrations in oceanic basalts (e.g. Ruzié et al. 2012). The estimated chlorine OIB source mantle concentration is in almost perfect agreement with primitive mantle estimates (Palme and O'Neill 2003). If we expect an OIB source mantle slightly depleted in incompatible elements, this suggests that at least small amounts of chlorine are recycled deep

  20. Target-specific porphyrin-loaded hybrid nanoparticles to improve photodynamic therapy for cancer treatment

    NASA Astrophysics Data System (ADS)

    Vivero-Escoto, Juan L.; Vega, Daniel L.

    2017-02-01

    Photodynamic therapy (PDT) has emerged as an alternative approach to chemotherapy and radiotherapy for cancer treatment. The photosensitizer (PS) is perhaps the most critical component of PDT, and continues to be an area of intense scientific research. Traditionally, PS molecules like porphyrins have dominated the field. Nevertheless, these PS agents have several disadvantages, with low water solubility, poor light absorption, and reduced selectivity for targeted tissues being some of the main drawbacks. Polysilsesquioxane (PSilQ) nanoparticles provide an interesting platform for developing PS-loaded hybrid nanocarriers. Several advantages can be foreseen by using this platform such as carrying a large payload of PS molecules; their surface and composition can be tailored to develop multifunctional systems (e.g. target-specific); and due to their small size, nanoparticles can penetrate deep into tissues and be readily internalized by cells. In this work, porphyrin-loaded PSilQ nanoparticles with a high payload of photosensitizers were synthesized, characterized, and applied in vitro. The network of this nanomaterial is formed by porphyrin-based photosensitizers chemically connected via a redox-responsive linker. Under reducing environment such as the one found in cancer cells the nanoparticles can be degraded to efficiently release single photosensitizers in the cytoplasm. The platform was further functionalized with polyethylene glycol (PEG) and folic acid as targeting ligand to improve its biocompatibility and target specificity toward cancer cells overexpressing folate receptors. The effectiveness of this porphyrin-based hybrid nanomaterial was successfully demonstrated in vitro using MDA-MB-231 breast cancer cell line.

  1. Halogenated volatile organic compounds from the use of chlorine-bleach-containing household products.

    PubMed

    Odabasi, Mustafa

    2008-03-01

    Sodium hypochlorite (NaOCl) and many organic chemicals contained in household cleaning products may react to generate halogenated volatile organic compounds (VOCs). Halogenated VOC emissions from eight different chlorine bleach containing household products (pure and diluted) were investigated by headspace experiments. Chloroform and carbon tetrachloride were the leading compounds along with several halogenated compounds in the headspace of chlorine bleach products. One of the most surprising results was the presence of carbon tetrachloride (a probable human carcinogen and a powerful greenhouse gas that was banned for household use by the U.S. Food and Drug Administration) in very high concentrations (up to 101 mg m(-3)). By mixing surfactants or soap with NaOCl, it was shown that the formation of carbon tetrachloride and several other halogenated VOCs is possible. In addition to quantitatively determined halogenated VOCs (n = 15), several nitrogen-containing (n = 4), chlorinated (n = 10), oxygenated compounds (n = 22), and hydrocarbons (n = 14) were identified in the headspace of bleach products. Among these, 1,1-dichlorobutane and 2-chloro-2-nitropropane were the most abundant chlorinated VOCs, whereas trichloronitromethane and hexachloroethane were the most frequently detected ones. Indoor air halogenated VOC concentrations resulting from the use of four selected household products were also measured before, during, and 30 min after bathroom, kitchen, and floor cleaning applications. Chloroform (2.9-24.6 microg m(-3)) and carbon tetrachloride (0.25-459 microg m(-3)) concentrations significantly increased during the use of bleach containing products. During/ before concentration ratios ranged between 8 and 52 (25 +/- 14, average +/- SD) for chloroform and 1-1170 (146 +/- 367, average +/- SD) for carbon tetrachloride, respectively. These results indicated that the bleach use can be important in terms of inhalation exposure to carbon tetrachloride, chloroform and

  2. Vibrational and electronic circular dichroism study of the interactions of cationic porphyrins with (dG-dC)10 and (dA-dT)10.

    PubMed

    Nový, Jakub; Urbanová, Marie

    2007-03-01

    The interactions of two different porphyrins, without axial ligands-5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin-Cu(II) tetrachloride (Cu(II)TMPyP) and with bulky meso substituents-5,10,15,20-tetrakis(N,N,N-trimethylanilinium-4-yl)porphyrin tetrachloride (TMAP), with (dG-dC)10 and (dA-dT)10 were studied by combination of vibrational circular dichroism (VCD) and electronic circular dichroism (ECD) spectroscopy at different [oligonucleotide]/[porphyrin] ratios, where [oligonucleotide] and [porphyrin] are the concentrations of oligonucleotide per base-pair and porphyrin, respectively. The combination of VCD and ECD spectroscopy enables us to identify the types of interactions, and to specify the sites of interactions: The intercalative binding mode of Cu(II)TMPyP with (dG-dC)(10), which has been well described, was characterized by a new VCD "marker" and it was shown that the interaction of Cu(II)TMPyP with (dA-dT)10 via external binding to the phosphate backbone and major groove binding caused transition from the B to the non-B conformer. TMAP interacted with the major groove of (dG-dC)10, was semi-intercalated into (dA-dT)10, and caused significant variation in the structure of both oligonucleotides at the higher concentration of porphyrin. The spectroscopic techniques used in this study revealed that porphyrin binding with AT sequences caused substantial variation of the DNA structure. It was shown that VCD spectroscopy is an effective tool for the conformational studies of nucleic acid-porphyrin complexes in solution. (c) 2007 Wiley Periodicals, Inc.

  3. The Role of Halogens in High-Grade Metamorphism and Anatexis

    NASA Astrophysics Data System (ADS)

    Aranovich, L.; Safonov, O.

    2016-12-01

    We review factors controlling the distribution of the two major halogens, F and Cl, in high-grade metamorphic rocks; their compositional correlations and partitioning between minerals; experimental data on stability and phase equilibria of the halogen-bearing minerals; the influence of halogens on Fe-Mg exchange reactions; and the means of estimating concentrations/activity of halogen species concentration/ activity in the fluid phase ("chlorimetry and fluorimetry") via calculation of equilibrium conditions for mineral assemblages containing halogen-bearing phases. Clear negative correlation between the F content and XFe=Fe/(Fe+Mg) suggests that natural biotite and amphibole obey the Fe-F avoidance rule. A strong positive correlation exists between K and Cl in amphibole. A scattering of points on the XFe -Cl and TiO2- Cl diagrams indicate the possible involvement of an exotic Cl-rich phase (fluid or melt) during the formation of Cl-bearing biotite and amphibole. Fluorine and Cl substituting for OH-groups substantially stabilize minerals relative to dehydration and melting. They should also strongly affect partitioning of Fe and Mg between biotite, amphibole and anhydrous minerals. This effect is quantified for Fe-Mg exchange reactions involving biotite (Zhu and Sverjensky, 1992), but remains to be evaluated for amphibole. Calculations based on recent thermodynamic systematics show that the relatively Mg-rich, Cl-poor biotite (for example, XFe = 0.4 and about 0.2 wt.% Cl) may coexist with a fairly Cl-rich fluid, i.e. total Cl/(Cl+H2O) from 0.1-0.3, depending on the assemblage, under granulite facies P-T conditions. Alkali (and Ca) metasomatism caused by interaction of high grade rocks with halogen-bearing fluids has major impact on the subsolidus phase transformations and melting processes during high-grade metamorphism and anatexis. For example, an increase in sodium content in plagioclase (Pl) by 20 mol% due to infiltration of Na- fluid into the quartz (Qtz

  4. Synthesis, spectroscopic, and photophysical characterization and photosensitizing activity toward prokaryotic and eukaryotic cells of porphyrin-magainin and -buforin conjugates.

    PubMed

    Dosselli, Ryan; Ruiz-González, Rubén; Moret, Francesca; Agnolon, Valentina; Compagnin, Chiara; Mognato, Maddalena; Sella, Valentina; Agut, Montserrat; Nonell, Santi; Gobbo, Marina; Reddi, Elena

    2014-02-27

    Cationic antimicrobial peptides (CAMPs) and photodynamic therapy (PDT) are attractive tools to combat infectious diseases and to stem further development of antibiotic resistance. In an attempt to increase the efficiency of bacteria inactivation, we conjugated a PDT photosensitizer, cationic or neutral porphyrin, to a CAMP, buforin or magainin. The neutral and hydrophobic porphyrin, which is not photoactive per se against Gram-negative bacteria, efficiently photoinactivated Escherichia coli after conjugation to either buforin or magainin. Conjugation to magainin resulted in the considerable strengthening of the cationic and hydrophilic porphyrin's interaction with the bacterial cells, as shown by the higher bacteria photoinactivation activity retained after washing the bacterial suspension. The porphyrin-peptide conjugates also exhibited strong interaction capability as well as photoactivity toward eukaryotic cells, namely, human fibroblasts. These findings suggest that these CAMPs have the potential to carry drugs and other types of cargo inside mammalian cells similar to cell-penetrating peptides.

  5. Halogenation of Hydraulic Fracturing Additives in the Shale Well Parameter Space

    NASA Astrophysics Data System (ADS)

    Sumner, A. J.; Plata, D.

    2017-12-01

    Horizontal Drilling and Hydraulic fracturing (HDHF) involves the deep-well injection of a `fracking fluid' composed of diverse and numerous chemical additives designed to facilitate the release and collection of natural gas from shale plays. The potential impacts of HDHF operations on water resources and ecosystems are numerous, and analyses of flowback samples revealed organic compounds from both geogenic and anthropogenic sources. Furthermore, halogenated chemicals were also detected, and these compounds are rarely disclosed, suggesting the in situ halogenation of reactive additives. To test this transformation hypothesis, we designed and operated a novel high pressure and temperature reactor system to simulate the shale well parameter space and investigate the chemical reactivity of twelve commonly disclosed and functionally diverse HDHF additives. Early results revealed an unanticipated halogenation pathway of α-β unsaturated aldehyde, Cinnamaldehyde, in the presence of oxidant and concentrated brine. Ongoing experiments over a range of parameters informed a proposed mechanism, demonstrating the role of various shale-well specific parameters in enabling the demonstrated halogenation pathway. Ultimately, these results will inform a host of potentially unintended interactions of HDHF additives during the extreme conditions down-bore of a shale well during HDHF activities.

  6. 40 CFR 721.8675 - Halogenated pyridines.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8675 Halogenated pyridines. (a) Chemical substances and significant new uses subject to... subject to reporting under this section for the significant new uses described in paragraph (a)(1)(i) of...

  7. 40 CFR 721.8675 - Halogenated pyridines.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8675 Halogenated pyridines. (a) Chemical substances and significant new uses subject to... subject to reporting under this section for the significant new uses described in paragraph (a)(1)(i) of...

  8. 40 CFR 721.8675 - Halogenated pyridines.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8675 Halogenated pyridines. (a) Chemical substances and significant new uses subject to... subject to reporting under this section for the significant new uses described in paragraph (a)(1)(i) of...

  9. Nanoparticles with Embedded Porphyrin Photosensitizers for Photooxidation Reactions and Continuous Oxygen Sensing.

    PubMed

    Kubát, Pavel; Henke, Petr; Berzediová, Veronika; Štěpánek, Miroslav; Lang, Kamil; Mosinger, Jiří

    2017-10-18

    We report the synthesis and characterization of sulfonated polystyrene nanoparticles (average diameter 30 ± 14 nm) with encapsulated 5,10,15,20-tetraphenylporphyrin or ionically entangled tetracationic 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin, their photooxidation properties, and the application of singlet oxygen-sensitized delayed fluorescence (SODF) in oxygen sensing. Both types of nanoparticles effectively photogenerated singlet oxygen, O 2 ( 1 Δ g ). The O 2 ( 1 Δ g ) phosphorescence, transient absorption of the porphyrin triplet states, and SODF signals were monitored using time-resolved spectroscopic techniques. The SODF intensity depended on the concentration of the porphyrin photosensitizer and dissolved oxygen and on the temperature. After an initial period (a few microseconds), the kinetics of the SODF process can be approximated as a monoexponential function, and the apparent SODF lifetimes can be correlated with the oxygen concentration. The oxygen sensing based on SODF allowed measurement of the dissolved oxygen in aqueous media in the broad range of oxygen concentrations (0.2-38 mg L -1 ). The ability of both types of nanoparticles to photooxidize external substrates was predicted by the SODF measurements and proven by chemical tests. The relative photooxidation efficacy was highest at a low porphyrin concentration, as indicated by the highest fluorescence quantum yield (Φ F ), and it corresponds with negligible inner filter and self-quenching effects. The photooxidation abilities were sensitive to the influence of temperature on the diffusion and solubility of oxygen in both polystyrene and water media and to the rate constant of the O 2 ( 1 Δ g ) reaction with a substrate. Due to their efficient photogeneration of cytotoxic O 2 ( 1 Δ g ) at physiological temperatures and their oxygen sensing via SODF, both types of nanoparticles are promising candidates for biomedical applications.

  10. Inorganic Halogen Oxidizer Research

    DTIC Science & Technology

    1975-02-26

    K. 0. Christe and C. J. Schack, Advances Inorg. Chem. Radiochem. 15. "The NF * Radical Cation. Esr Studies of Radiation Effects in NF„+ Salts...and 25°) in a wide variety of polar and nonpolar solvents, such as aqueous solutions, alcohols, ketones , esters, ethers , and aromatic and halogenated... Studies of Radiation Effects in NF, Salts = 4 S. P. Mishra, M. C R. Symons, K. 0. Christe, R. D. Wilson and R. I. Wagner Received. . . August .9

  11. Theoretical model for optical properties of porphyrin

    NASA Astrophysics Data System (ADS)

    Phan, Anh D.; Nga, Do T.; Phan, The-Long; Thanh, Le T. M.; Anh, Chu T.; Bernad, Sophie; Viet, N. A.

    2014-12-01

    We propose a simple model to interpret the optical absorption spectra of porphyrin in different solvents. Our model successfully explains the decrease in the intensity of optical absorption at maxima of increased wavelengths. We also prove the dependence of the intensity and peak positions in the absorption spectra on the environment. The nature of the Soret band is supposed to derive from π plasmon. Our theoretical calculations are consistent with previous experimental studies.

  12. Synthesis and in vitro phototoxicity of multifunctional Zn(II)meso-tetrakis(4-carboxyphenyl)porphyrin-coated gold nanoparticles assembled via axial coordination with imidazole ligands.

    PubMed

    Alea-Reyes, María E; Penon, Oriol; García Calavia, Paula; Marín, María J; Russell, David A; Pérez-García, Lluïsa

    2018-07-01

    Metalloporphyrins are extensively investigated for their ability to form reactive oxygen species and as potent photosensitisers for use in photodynamic therapy. However, their hydrophobicity generally causes solubility issues concerning in vivo delivery due to lack of distribution and low clearance from the body. Immobilising porphyrins on carriers, such as gold nanoparticles (GNP), can overcome some of these drawbacks. The mode of assembling the porphyrins to the carrier influences the properties of the resulting drug delivery systems. We describe the synthesis and characterisation of new porphyrin decorated water soluble GNP and we explore Zn-imidazole axial coordination as the mode of linking the porphyrin to the metallic core of the nanoparticles. Quantification of singlet oxygen production, toxicity in dark, cellular uptake by SK-BR-3 cells and phototoxicity have been assessed. Axial coordination limits the number of porphyrins on the gold surface, reduces the formation of aggregates, and diminishes metal exchange in the porphyrin, all of which contribute to enhance the efficiency of singlet oxygen generation from the immobilised porphyrin. In vitro experiments on SK-BR-3 cells reveal a fast uptake followed by more than 80% cell death after irradiation with low doses of light. Copyright © 2018 Elsevier Inc. All rights reserved.

  13. Theoretical study of photoinduced epoxidation of olefins catalyzed by ruthenium porphyrin.

    PubMed

    Ishikawa, Atsushi; Sakaki, Shigeyoshi

    2011-05-12

    Epoxidation of olefin by [Ru(TMP)(CO)(O)](-) (TMP = tetramesitylporphine), which is a key step of the photocatalyzed epoxidation of olefin by [Ru(TMP)(CO)], is studied mainly with the density functional theory (DFT) method, where [Ru(Por)(CO)] is employed as a model complex (Por = unsubstituted porphyrin). The CASSCF method was also used to investigate the electronic structure of important species in the catalytic cycle. In all of the ruthenium porphyrin species involved in the catalytic cycle, the weight of the main configuration of the CASSCF wave function is larger than 85%, suggesting that the static correlation is not very large. Also, unrestricted-DFT-calculated natural orbitals are essentially the same as CASSCF-calculated ones, here. On the basis of these results, we employed the DFT method in this work. Present computational results show characteristic features of this reaction, as follows: (i) The epoxidation reaction occurs via carboradical-type transition state. Neither carbocation-type nor concerted oxene-insertion-type character is observed in the transition state. (ii) Electron and spin populations transfer from the olefin moiety to the porphyrin ring in the step of the C-O bond formation. (iii) Electron and spin populations of the olefin and porphyrin moieties considerably change around the transition state. (iv) The atomic and spin populations of Ru change little in the reaction, indicating that the Ru center keeps the +II oxidation state in the whole catalytic cycle. (v) The stability of the olefin adduct [Ru(Por)(CO)(O)(olefin)](-) considerably depends on the kind of olefin, such as ethylene, n-hexene, and styrene. In particular, styrene forms a stable olefin adduct. And, (vi) interestingly, the difference in the activation barrier among these olefins is small in the quantitative level (within 5 kcal/mol), indicating that this catalyst can be applied to various substrates. This is because the stabilities and electronic structures of both the

  14. Perturbations in DNA structure upon interaction with porphyrins revealed by chemical probes, DNA footprinting and molecular modelling.

    PubMed

    Ford, K G; Neidle, S

    1995-06-01

    The interactions of several porphyrins with a 74 base-pair DNA sequence have been examined by footprinting and chemical protection methods. Tetra-(4-N-methyl-(pyridyl)) porphyrin (TMPy), two of its metal complexes and tetra-(4-trimethylanilinium) porphyrin (TMAP) bind to closely similar AT-rich sequences. The three TMPy ligands produce modest changes in DNA structure and base accessibility on binding, in contrast to the large-scale conformational changes observed with TMAP. Molecular modelling studies have been performed on TMPy and TMAP bound in the AT-rich minor groove of an oligonucleotide. These have shown that significant structural change is needed to accommodate the bulky trimethyl substituent groups of TMAP, in contrast to the facile minor groove fit of TMPy.

  15. Volatile Halogenated Organic Compounds Released to Seawater from Temperate Marine Macroalgae

    NASA Astrophysics Data System (ADS)

    Gschwend, Philip M.; Macfarlane, John K.; Newman, Kathleen A.

    1985-03-01

    Volatile halogenated organic compounds synthesized by various industrial processes are troublesome pollutants because they are persistent in terrestrial ecosystems and because they may be present in sufficient quantities to alter the natural atmospheric cycles of the halogens. Certain of these compounds, including polybromomethanes and several previously unobserved alkyl monohalides and dihalides, appear to be natural products of the marine environment. A variety of temperate marine macroalgae (the brown algae Ascophyllum nodosum and Fucus vesiculosis, the green algae Enteromorpha linza and Ulva lacta, and the red alga Gigartina stellata) not only contain volatile halogenated organic compounds but also release them to seawater at rates of nanograms to micrograms of each compound per gram of dry algae per day. The macroalgae may be an important source of bromine-containing material released to the atmosphere.

  16. Identification and Spectroscopic Characterization of Nonheme Iron(III) Hypochlorite Intermediates.

    PubMed

    Draksharapu, Apparao; Angelone, Davide; Quesne, Matthew G; Padamati, Sandeep K; Gómez, Laura; Hage, Ronald; Costas, Miquel; Browne, Wesley R; de Visser, Sam P

    2015-03-27

    Fe III -hypohalite complexes have been implicated in a wide range of important enzyme-catalyzed halogenation reactions including the biosynthesis of natural products and antibiotics and post-translational modification of proteins. The absence of spectroscopic data on such species precludes their identification. Herein, we report the generation and spectroscopic characterization of nonheme Fe III -hypohalite intermediates of possible relevance to iron halogenases. We show that Fe III -OCl polypyridylamine complexes can be sufficiently stable at room temperature to be characterized by UV/Vis absorption, resonance Raman and EPR spectroscopies, and cryo-ESIMS. DFT methods rationalize the pathways to the formation of the Fe III -OCl, and ultimately Fe IV =O, species and provide indirect evidence for a short-lived Fe II -OCl intermediate. The species observed and the pathways involved offer insight into and, importantly, a spectroscopic database for the investigation of iron halogenases.

  17. Identification and Spectroscopic Characterization of Nonheme Iron(III) Hypochlorite Intermediates**

    PubMed Central

    Draksharapu, Apparao; Angelone, Davide; Quesne, Matthew G; Padamati, Sandeep K; Gómez, Laura; Hage, Ronald; Costas, Miquel; Browne, Wesley R; de Visser, Sam P

    2015-01-01

    FeIII–hypohalite complexes have been implicated in a wide range of important enzyme-catalyzed halogenation reactions including the biosynthesis of natural products and antibiotics and post-translational modification of proteins. The absence of spectroscopic data on such species precludes their identification. Herein, we report the generation and spectroscopic characterization of nonheme FeIII–hypohalite intermediates of possible relevance to iron halogenases. We show that FeIII-OCl polypyridylamine complexes can be sufficiently stable at room temperature to be characterized by UV/Vis absorption, resonance Raman and EPR spectroscopies, and cryo-ESIMS. DFT methods rationalize the pathways to the formation of the FeIII-OCl, and ultimately FeIV=O, species and provide indirect evidence for a short-lived FeII-OCl intermediate. The species observed and the pathways involved offer insight into and, importantly, a spectroscopic database for the investigation of iron halogenases. PMID:25663379

  18. Tunneling electron induced molecular electroluminescence from individual porphyrin J-aggregates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Meng, Qiushi; Zhang, Chao; Zhang, Yang, E-mail: zhyangnano@ustc.edu.cn, E-mail: zcdong@ustc.edu.cn

    2015-07-27

    We investigate molecular electroluminescence from individual tubular porphyrin J-aggregates on Au(111) by tunneling electron excitations in an ultrahigh-vacuum scanning tunneling microscope (STM). High-resolution STM images suggest a spiral tubular structure for the porphyrin J-aggregate with highly ordered “brickwork”-like arrangements. Such aggregated nanotube is found to behave like a self-decoupled molecular architecture and shows red-shifted electroluminescence characteristics of J-aggregates originated from the delocalized excitons. The positions of the emission peaks are found to shift slightly depending on the excitation sites, which, together with the changes in the observed spectral profiles with vibronic progressions, suggest a limited exciton coherence number within severalmore » molecules. The J-aggregate electroluminescence is also found unipolar, occurring only at negative sample voltages, which is presumably related to the junction asymmetry in the context of molecular excitations via the carrier injection mechanism.« less

  19. Halogen free benzoxazine based curable compositions for high T.sub.g applications

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tietze, Roger; Nguyen, Yen-Loan

    A method for forming a halogen-free curable composition containing a benzoxazine monomer, at least one epoxy resin, a catalyst, a toughening agent and a solvent. The halogen-free curable composition is especially suited for use in automobile and aerospace applications since the composition, upon curing, produces a composite having a high glass transition temperature.

  20. In-vivo characterization of endogenous porphyrin fluorescence from DMBA-treated Swiss Albino mice skin carcinogenesis for measuring tissue transformation

    NASA Astrophysics Data System (ADS)

    Ganesan, Singaravelu; Ebenezar, Jeyasingh; Hemamalini, Srinivasan; Aruna, Prakasa R.

    2002-05-01

    Steady state fluorescence spectroscopic characterization of endogenous porphyrin emission from DMBA treated skin carcinogenesis in Swiss albino mice was carried out. The emission of endogenous porphyrin from normal and abnormal skin tissues was studied both in the presence and absence of exogenous ALA to compare the resultant porphyrin emission characterictics. The mice skin is excited at 405nm and emission spectra are scanned from 430 to 700nm. The average fluorescence emission spectra of mice skin at normal and various tissues transformation conditions were found to be different. Two peaks around 460nm and 636nm were observed and they may be attributed to NADH, Elastin and collagen combination and endogenous porphyrin emission. The intensity at 636nm increases as the stage of the cancer increases. Although exogenous ALA enhances the PPIX level in tumor, the synthesis of PPIX was also found in normal surrounding skin, in fact, with higher concentration than that of tumor tissues.

  1. α-Halogenated oxaphosphinanes: Synthesis, unexpected reactions and evaluation as inhibitors of cancer cell proliferation.

    PubMed

    Babouri, Rachida; Rolland, Marc; Sainte-Catherine, Odile; Kabouche, Zahia; Lecouvey, Marc; Bakalara, Norbert; Volle, Jean-Noël; Virieux, David; Pirat, Jean-Luc

    2015-11-02

    This paper describes the preparation and the biological evaluation of α-halogenated oxaphosphinanes. These halogen derivatives were synthetized from a short and stereoselective synthetic sequence starting by previously described hydroxy-precursors 1 and 2 with respectively a glucose and mannose-like configuration. The in vitro biological tests of these unnatural halogenated phosphinosugars, on several cell lines, highlighted, for some of them, their antiproliferative and anti migration and invasion properties at nanomolar concentration. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  2. Symmetric and asymmetric halogen-containing metallocarboranylporphyrins and uses thereof

    DOEpatents

    Miura, Michiko; Wu, Haitao

    2013-05-21

    The present invention is directed to low toxicity boronated compounds and methods for their use in the treatment, visualization, and diagnosis of tumors. More specifically, the present invention is directed to low toxicity halogenated, carborane-containing 5,10,15,20-tetraphenylporphyrin compounds and methods for their use particularly in boron neutron capture therapy (BNCT) and photodynamic therapy (PDT) for the treatment of tumors of the brain, head and neck, and surrounding tissue. The invention is also directed to using these halogenated, carborane-containing tetraphenylporphyrin compounds in methods of tumor imaging and/or diagnosis such as MRI, SPECT, or PET.

  3. Structure-Energy Relationships of Halogen Bonds in Proteins.

    PubMed

    Scholfield, Matthew R; Ford, Melissa Coates; Carlsson, Anna-Carin C; Butta, Hawera; Mehl, Ryan A; Ho, P Shing

    2017-06-06

    The structures and stabilities of proteins are defined by a series of weak noncovalent electrostatic, van der Waals, and hydrogen bond (HB) interactions. In this study, we have designed and engineered halogen bonds (XBs) site-specifically to study their structure-energy relationship in a model protein, T4 lysozyme. The evidence for XBs is the displacement of the aromatic side chain toward an oxygen acceptor, at distances that are equal to or less than the sums of their respective van der Waals radii, when the hydroxyl substituent of the wild-type tyrosine is replaced by a halogen. In addition, thermal melting studies show that the iodine XB rescues the stabilization energy from an otherwise destabilizing substitution (at an equivalent noninteracting site), indicating that the interaction is also present in solution. Quantum chemical calculations show that the XB complements an HB at this site and that solvent structure must also be considered in trying to design molecular interactions such as XBs into biological systems. A bromine substitution also shows displacement of the side chain, but the distances and geometries do not indicate formation of an XB. Thus, we have dissected the contributions from various noncovalent interactions of halogens introduced into proteins, to drive the application of XBs, particularly in biomolecular design.

  4. Surface-confined Ullmann coupling of thiophene substituted porphyrins

    NASA Astrophysics Data System (ADS)

    Beggan, J. P.; Boyle, N. M.; Pryce, M. T.; Cafolla, A. A.

    2015-09-01

    The covalent coupling of (5,10,15,20-tetrabromothien-2-ylporphyrinato)zinc(II) (TBrThP) molecules on the Ag(111) surface has been investigated under ultra-high-vacuum conditions, using scanning tunnelling microscopy and x-ray photoelectron spectroscopy. The findings provide atomic-level insight into surface-confined Ullmann coupling of thiophene substituted porphyrins, analyzing the progression of organometallic intermediate to final coupled state. Adsorption of the TBrThP molecules on the Ag(111) surface at room temperature is found to result in the reductive dehalogenation of the bromothienyl substituents and the subsequent formation of single strand and crosslinked coordination networks. The coordinated substrate atoms bridge the proximal thienyl groups of the organometallic intermediate, while the cleaved bromine atoms are bound on the adjacent Ag(111) surface. The intermediate complex displays a thermal lability at ˜423 K that results in the dissociation of the proximal thienyl groups with the concomitant loss of the surface bound bromine. At the thermally induced dissociation of the intermediate complex the resultant thienylporphyrin derivatives covalently couple, leading to the formation of a polymeric network of thiophene linked and meso-meso fused porphyrins.

  5. Porphyrin Based neuton capture agents for cancer therapy

    DOEpatents

    Vicente, Maria Da; Shetty, Shankar Jayaram; Jaquinod, Laurent; Smith, Kevin M.

    2006-06-27

    The invention describes the synthesis of a panel of novel carbon-carbon linked carboranyl-containing 5,10,15,20-tetraphenylporphyrins bearing 25–44% boron by weight. In certain embodiments, a phenyl porphyrin compound has a carboranyl group attached to the phenyl group by a carbon-carbon linkage, wherein the phenyl group corresponds to the following formula embedded image
    where R7 through R11 are hydrogen, a carboranyl group, or are selected from the group consisting of hydroxyl, NMe3+, PMePh2+, PO(OH)2, SO3H, COOH, and NH2. In this embodiment, the carboranyl group is attached to the phenyl group by a carbon-carbon linkage, either one or two of R7 through R11 are other than hydrogen; and the phenyl porphyrin compound contains at least one phenyl group having at least one of said carboranyl groups.

  6. Aggregation and metal-complexation behaviour of THPP porphyrin in ethanol/water solutions as function of pH

    NASA Astrophysics Data System (ADS)

    Zannotti, Marco; Giovannetti, Rita; Minofar, Babak; Řeha, David; Plačková, Lydie; D'Amato, Chiara A.; Rommozzi, Elena; Dudko, Hanna V.; Kari, Nuerguli; Minicucci, Marco

    2018-03-01

    The effect of pH change on 5,10,15,20-Tetrakis(4-hydroxyphenyl)-21H,23H-porphine (THPP) with its aggregation as function of water-ethanol mixture was studied with UV-vis, fluorescence, Raman and computational analysis. In neutral pH, THPP was present as free-base and, increasing the water amount, aggregation occurred with the formation of H- and J-aggregates. The aggregation constant and the concentration of dimers were calculated, other information about the dimer aggregation were evaluated by computational study. In acidic pH, by the insertions of two hydrogens in the porphyrin rings, the porphyrin changed its geometry with a ring deformation confirmed by red-shifted spectrum and quenching in fluorescence; at this low pH, increasing the water amount, the acidic form (THPPH2)2 + resulted more stable due to a polar environment with stronger interaction by hydrogen bonding. In basic pH, reached by NH4OH, THPP porphyrin was able to react with alkali metals in order to form sitting-atop complex (M2THPP) confirmed by the typical absorption spectrum of metallo-porphyrin, Raman spectroscopy and by computational analysis.

  7. Formation of halogen-induced secondary organic aerosol (XOA)

    NASA Astrophysics Data System (ADS)

    Kamilli, Katharina; Ofner, Johannes; Zetzsch, Cornelius; Held, Andreas

    2013-04-01

    Reactive halogen species (RHS) are very important due to their potential of stratospheric ozone depletion and surface ozone destruction. RHS seem to interact with precursors of secondary organic aerosol (SOA) similarly to common atmospheric oxidants like OH radicals and ozone. The potential interaction of RHS with preformed SOA has recently been studied (Ofner et al., 2012). Although aerosol formation from reaction of RHS with typical SOA precursors was previously studied (e.g. Cai et al., 2006), no data are available on bromine-induced aerosol formation from organic precursors yet. An aerosol smog-chamber was used to examine the halogen-induced secondary organic aerosol (XOA) formation under atmospheric conditions using simulated sunlight. With a concentration of 10 ppb for the organic precursor, 2 ppb for molecular chlorine, and 10 ppb for molecular bromine, the experimental setup is close to ambient conditions. By combined measurements of the aerosol size distribution, ozone and NOx mixing ratios, as well as the decay of the organic precursor, aerosol yields and aerosol growth rates were determined. The decay of the organic precursor was analyzed by capillary gas chromatography coupled with flame-ionization detection (GC-FID) and the aerosol size distribution was measured using a Scanning Mobility Particle Sizer (SMPS). Additionally, with the decay rate of the precursor and the calculated photolysis rates of molecular halogen species, based on the well-known spectrum of the solar simulator, mechanistic details on the XOA formation pathways can be determined. We observed XOA formation even at very low precursor and RHS concentrations with a diameter mode at 10-20 nm and a number concentration up to 1000000 particles cm-3. While the XOA formation from chlorine is very rapid, the interaction of bromine with the organic precursors is about five times slower. The aerosol yield reached maximum values of 0.01 for the reaction of chlorine with α-pinene and 0.0004 for

  8. Controllable and reversible inversion of the electronic structure in nickel N-confused porphyrin: a case when MCD matters.

    PubMed

    Sripothongnak, Saovalak; Ziegler, Christopher J; Dahlby, Michael R; Nemykin, Victor N

    2011-08-01

    Nickel N-confused tetraphenylporphyrin, 1, and nickel 2-N-methyl-N-confused tetraphenylporphyrin, 1-Me, exhibit unusual sign-reversed (positive-to-negative intensities in ascending energy) MCD spectra in the Q-type band region, suggesting a rare ΔHOMO < ΔLUMO relationship between π and π* MOs in the porphyrin core. Simple and reversible deprotonation of the external NH proton in 1 dramatically changes the electronic structure of the porphyrin core into the ΔHOMO > ΔLUMO combination characteristic for the meso-(tetraaryl)porphyrins. DFT, time-dependent DFT, and semiempirical ZINDO/S calculations on 1, 1-Me, and 1(-) confirm the experimental finding and successfully explain the MCD pattern in the target compounds. © 2011 American Chemical Society

  9. Internalization of a C17α-alkynylestradiol-porphyrin conjugate into estrogen receptor positive MCF-7 breast cancer cells.

    PubMed

    Sadler, Sara; Persons, Kelly S; Jones, Graham B; Ray, Rahul

    2011-08-01

    We hypothesized that expression of nuclear estrogen receptor (ER) in hormone-sensitive breast cancer cells could be harnessed synergistically with the tumor-accumulating effect of porphyrins to selectively deliver estrogen-porphyrin conjugates into breast tumor cells, and preferentially kill tumor cells upon exposure to visible light. In this study we synthesized a conjugate of C(17α)-alkynylestradiol and pyropheophorbide and demonstrated that this conjugate is internalized by ER-positive MCF-7 cells while pyropheophorbide did not, suggesting an ER-mediated uptake and internalization of the conjugate by incipient nuclear ER in MCF-7 cells. This study is a direct demonstration of our hypothesis about ER-mediated internalization of estrogen-porphyrin conjugates. Copyright © 2011. Published by Elsevier Ltd.

  10. Synthesis, optical and electrochemical properties of Zn-porphyrin for dye sensitized solar cell applications

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kotteswaran, S.; Pandian, M. Senthil; Ramasamy, P., E-mail: ramasamyp@ssn.edu.in

    2016-05-23

    Zn-Porphyrin dye has been synthesized by the reaction between aldehydes and pyrrole. The dye structure was confirmed by {sup 1}H NMR, {sup 13}C NMR spectrum. The functional group of the dye molecule was confirmed by FTIR spectrum. The UV-Vis-NIR absorption spectrum of Zn-Porphyrin in DMF solution was recorded in spectrophotometer. The UV-Vis NIR spectrum of dye exhibits a strong Soret band and Q-band. Cyclic Voltammograms were obtained with three electrode systems: Pt as counter electrode, saturated calomel used as a reference electrode and glassy carbon as working electrode at a scan rate of 100 mV/s. The curves recorded the oxidation ofmore » 0.5 mM compound Zn-Porphyrin in a dichloromethane solution containing 0.1M TBAP as supporting electrolyte, reveal two successive quasi reversible redox couples with the first anodic and cathodic peak potentials of -0.2 V and -1 V. The second anodic and cathodic peak potentials are 0.82 V and 0.01 V respectively.« less

  11. Saddle-shaped porphyrins for dye-sensitized solar cells: new insight into the relationship between nonplanarity and photovoltaic properties.

    PubMed

    Shahroosvand, Hashem; Zakavi, Saeed; Sousaraei, Ahmad; Eskandari, Mortaza

    2015-03-07

    We report on the theoretical and experimental studies of the new dye-sensitized solar cells functionalized with 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin zinc(II) complexes bearing 2- and 8-bromo substituents at the β positions. In agreement with the results of TD-DFT calculations, the absorption maxima of di- and octa-brominated Zn(II) complexes, ZnTCPPBr2 and ZnTCPPBr8, exhibited large red-shift compared to that of the non-brominated free base porphyrin (H2TCPP). Furthermore, DFT calculations showed that the higher stabilization of the LUMO levels relative to the HOMO ones makes the HOMO-LUMO gap of the brominated Zn-porphyrins models smaller compared to that of the nonbrominated counterparts, which explains the red shifts of the Soret and Q bands of the brominated compounds. Solar cells containing the new saddle-shaped Zn(II) porphyrins were subjected to analysis in a photovoltaic calibration laboratory to determine their solar to electric energy conversion. In this regard, we found that the overall conversion efficiency of ZnTCPPBr8 adsorbed on TiO2 nanocrystalline films was 5 times as large as that of ZnTCPPBr2 adsorbed on the same films. The effect of the increasing number of Br groups on the photovoltaic performance of the complexes was compared to the results of computational methods using ab initio DFT molecular dynamics simulations and quantum dynamics calculations of electronic relaxation to investigate the interfacial electron transfer (IET) in TCPPBrx/TiO2-anatase nanostructures. Better IET in ZnTCPPBr8 compared to ZnTCPPBr2, and in H2TCPP was evaluated from interfacial electron transfer (IET) simulations. The IET results indicate that electron injection in ZnTCPPBr8-TiO2 (τ = 25 fs) can be up to 5 orders of magnitude faster than ZnTCPPBr2-TiO2 (τ = 125 fs). Both experimental and theoretical results demonstrate that the increase of the number of bromo-substituents at the β-pyrrole positions of the porphyrin macrocycle created a new class of

  12. Skin Sensitizing Potency of Halogenated Platinum Salts.

    EPA Science Inventory

    The relationship between occupational exposure to halogenated platinum (Pt) salts and Pt-specific allergic sensitization is well-established. Although human case reports and clinical studies demonstrate that Pt salts are potent skin sensitizers, no studies have been published tha...

  13. Perturbations in the Photosynthetic Pigment Status Result in Photooxidation-Induced Crosstalk between Carotenoid and Porphyrin Biosynthetic Pathways

    PubMed Central

    Park, Joon-Heum; Tran, Lien H.; Jung, Sunyo

    2017-01-01

    Possible crosstalk between the carotenoid and porphyrin biosynthetic pathways under photooxidative conditions was investigated by using their biosynthetic inhibitors, norflurazon (NF) and oxyfluorfen (OF). High levels of protoporphyrin IX (Proto IX) accumulated in rice plants treated with OF, whereas Proto IX decreased in plants treated with NF. Both NF and OF treatments resulted in greater decreases in MgProto IX, MgProto IX methyl ester, and protochlorophyllide. Activities and transcript levels of most porphyrin biosynthetic enzymes, particularly in the Mg-porphyrin branch, were greatly down-regulated in NF and OF plants. In contrast, the transcript levels of GSA, PPO1, and CHLD as well as FC2 and HO2 were up-regulated in NF-treated plants, while only moderate increases in FC2 and HO2 were observed in the early stage of OF treatment. Phytoene, antheraxanthin, and zeaxanthin showed high accumulation in NF-treated plants, whereas other carotenoid intermediates greatly decreased. Transcript levels of carotenoid biosynthetic genes, PSY1 and PDS, decreased in response to NF and OF, whereas plants in the later stage of NF treatment exhibited up-regulation of BCH and VDE as well as recovery of PDS. However, perturbed porphyrin biosynthesis by OF did not noticeably influence levels of carotenoid metabolites, regardless of the strong down-regulation of carotenoid biosynthetic genes. Both NF and OF plants appeared to provide enhanced protection against photooxidative damage, not only by scavenging of Mg-porphyrins, but also by up-regulating FC2, HO2, and Fe-chelatase, particularly with increased levels of zeaxanthin via up-regulation of BCH and VDE in NF plants. On the other hand, the up-regulation of GSA, PPO1, and CHLD under inhibition of carotenogenic flux may be derived from the necessity to recover impaired chloroplast biogenesis during photooxidative stress. Our study demonstrates that perturbations in carotenoid and porphyrin biosynthesis coordinate the expression

  14. Perturbations in the Photosynthetic Pigment Status Result in Photooxidation-Induced Crosstalk between Carotenoid and Porphyrin Biosynthetic Pathways.

    PubMed

    Park, Joon-Heum; Tran, Lien H; Jung, Sunyo

    2017-01-01

    Possible crosstalk between the carotenoid and porphyrin biosynthetic pathways under photooxidative conditions was investigated by using their biosynthetic inhibitors, norflurazon (NF) and oxyfluorfen (OF). High levels of protoporphyrin IX (Proto IX) accumulated in rice plants treated with OF, whereas Proto IX decreased in plants treated with NF. Both NF and OF treatments resulted in greater decreases in MgProto IX, MgProto IX methyl ester, and protochlorophyllide. Activities and transcript levels of most porphyrin biosynthetic enzymes, particularly in the Mg-porphyrin branch, were greatly down-regulated in NF and OF plants. In contrast, the transcript levels of GSA, PPO1 , and CHLD as well as FC2 and HO2 were up-regulated in NF-treated plants, while only moderate increases in FC2 and HO2 were observed in the early stage of OF treatment. Phytoene, antheraxanthin, and zeaxanthin showed high accumulation in NF-treated plants, whereas other carotenoid intermediates greatly decreased. Transcript levels of carotenoid biosynthetic genes, PSY1 and PDS , decreased in response to NF and OF, whereas plants in the later stage of NF treatment exhibited up-regulation of BCH and VDE as well as recovery of PDS . However, perturbed porphyrin biosynthesis by OF did not noticeably influence levels of carotenoid metabolites, regardless of the strong down-regulation of carotenoid biosynthetic genes. Both NF and OF plants appeared to provide enhanced protection against photooxidative damage, not only by scavenging of Mg - porphyrins, but also by up-regulating FC2, HO2 , and Fe-chelatase, particularly with increased levels of zeaxanthin via up-regulation of BCH and VDE in NF plants. On the other hand, the up-regulation of GSA, PPO1 , and CHLD under inhibition of carotenogenic flux may be derived from the necessity to recover impaired chloroplast biogenesis during photooxidative stress. Our study demonstrates that perturbations in carotenoid and porphyrin biosynthesis coordinate the

  15. Impact of Enhanced Ozone Deposition and Halogen Chemistry on Tropospheric Ozone over the Northern Hemisphere.

    PubMed

    Sarwar, Golam; Gantt, Brett; Schwede, Donna; Foley, Kristen; Mathur, Rohit; Saiz-Lopez, Alfonso

    2015-08-04

    Fate of ozone in marine environments has been receiving increased attention due to the tightening of ambient air quality standards. The role of deposition and halogen chemistry is examined through incorporation of an enhanced ozone deposition algorithm and inclusion of halogen chemistry in a comprehensive atmospheric modeling system. The enhanced ozone deposition treatment accounts for the interaction of iodide in seawater with ozone and increases deposition velocities by 1 order of magnitude. Halogen chemistry includes detailed chemical reactions of organic and inorganic bromine and iodine species. Two different simulations are completed with the halogen chemistry: without and with photochemical reactions of higher iodine oxides. Enhanced deposition reduces mean summer-time surface ozone by ∼3% over marine regions in the Northern Hemisphere. Halogen chemistry without the photochemical reactions of higher iodine oxides reduces surface ozone by ∼15% whereas simulations with the photochemical reactions of higher iodine oxides indicate ozone reductions of ∼48%. The model without these processes overpredicts ozone compared to observations whereas the inclusion of these processes improves predictions. The inclusion of photochemical reactions for higher iodine oxides leads to ozone predictions that are lower than observations, underscoring the need for further refinement of the halogen emissions and chemistry scheme in the model.

  16. Selective Nitrate Recognition by a Halogen-Bonding Four-Station [3]Rotaxane Molecular Shuttle.

    PubMed

    Barendt, Timothy A; Docker, Andrew; Marques, Igor; Félix, Vítor; Beer, Paul D

    2016-09-05

    The synthesis of the first halogen bonding [3]rotaxane host system containing a bis-iodo triazolium-bis-naphthalene diimide four station axle component is reported. Proton NMR anion binding titration experiments revealed the halogen bonding rotaxane is selective for nitrate over the more basic acetate, hydrogen carbonate and dihydrogen phosphate oxoanions and chloride, and exhibits enhanced recognition of anions relative to a hydrogen bonding analogue. This elaborate interlocked anion receptor functions via a novel dynamic pincer mechanism where upon nitrate anion binding, both macrocycles shuttle from the naphthalene diimide stations at the periphery of the axle to the central halogen bonding iodo-triazolium station anion recognition sites to form a unique 1:1 stoichiometric nitrate anion-rotaxane sandwich complex. Molecular dynamics simulations carried out on the nitrate and chloride halogen bonding [3]rotaxane complexes corroborate the (1) H NMR anion binding results. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  17. Enhanced Catalytic Activity and Unexpected Products from the Oxidation of Cyclohexene by Organic Nanoparticles of 5,10,15,20-Tetrakis-(2,3,4,5,6-pentafluorophenyl)porphyrinatoiron(III) in Water by Using O2

    PubMed Central

    Smeureanu, Gabriela; Aggarwal, Amit; Soll, Clifford E.; Arijeloye, Julius; Malave, Erik

    2010-01-01

    The catalytic oxidation of alkenes by most iron porphyrins using a variety of oxygen sources, but generally not dioxygen, yields the epoxide with minor quantities of other products. The turnover numbers for these catalysts are modest, ranging from a few hundred to a few thousand depending on the porphyrin structure, axial ligands, and other reaction conditions. Halogenation of substituents increases the activity of the metalloporphyrin catalyst and/or makes it more robust to oxidative degradation. Oxidation of cyclohexene by 5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)porphyrinato iron(III), ([FeIII(tppf20)]) and H2O2 is typical of the latter: the epoxide is 99% of the product and turnover numbers are about 350.[1–4] Herein, we report that dynamic organic nanoparticles (ONPs) of [FeIII(tppf20)] with a diameter of 10 nm, formed by host–guest solvent methods, catalytically oxidize cyclohexene with O2 to yield only 2-cyclohexene-1-one and 2-cyclohexene-1-ol with approximately 10-fold greater turnover numbers compared to the non-aggregated metalloporphyrin in acetonitrile/methanol. These ONPs facilitate a greener reaction because the reaction solvent is 89% water and O2 is the oxidant in place of synthetic oxygen sources. This reactivity is unexpected because the metalloporphyrins are in close proximity and oxidative degradation of the catalyst should be enhanced, thus causing a significant decrease in catalytic turnovers. The allylic products suggest a different oxidative mechanism compared to that of the solvated metalloporphyrins. These results illustrate the unique properties of some ONPs relative to the component molecules or those attached to supports. PMID:19777510

  18. Porphyrins at interfaces

    NASA Astrophysics Data System (ADS)

    Auwärter, Willi; Écija, David; Klappenberger, Florian; Barth, Johannes V.

    2015-02-01

    Porphyrins and other tetrapyrrole macrocycles possess an impressive variety of functional properties that have been exploited in natural and artificial systems. Different metal centres incorporated within the tetradentate ligand are key for achieving and regulating vital processes, including reversible axial ligation of adducts, electron transfer, light-harvesting and catalytic transformations. Tailored substituents optimize their performance, dictating their arrangement in specific environments and mediating the assembly of molecular nanoarchitectures. Here we review the current understanding of these species at well-defined interfaces, disclosing exquisite insights into their structural and chemical properties, and also discussing methods by which to manipulate their intramolecular and organizational features. The distinct characteristics arising from the interfacial confinement offer intriguing prospects for molecular science and advanced materials. We assess the role of surface interactions with respect to electronic and physicochemical characteristics, and describe in situ metallation pathways, molecular magnetism, rotation and switching. The engineering of nanostructures, organized layers, interfacial hybrid and bio-inspired systems is also addressed.

  19. Singlet oxygen production by combining erythrosine and halogen light for photodynamic inactivation of Streptococcus mutans.

    PubMed

    Fracalossi, Camila; Nagata, Juliana Yuri; Pellosi, Diogo Silva; Terada, Raquel Sano Suga; Hioka, Noboru; Baesso, Mauro Luciano; Sato, Francielle; Rosalen, Pedro Luiz; Caetano, Wilker; Fujimaki, Mitsue

    2016-09-01

    Photodynamic inactivation of microorganisms is based on a photosensitizing substance which, in the presence of light and molecular oxygen, produces singlet oxygen, a toxic agent to microorganisms and tumor cells. This study aimed to evaluate singlet oxygen quantum yield of erythrosine solutions illuminated with a halogen light source in comparison to a LED array (control), and the photodynamic effect of erythrosine dye in association with the halogen light source on Streptococcus mutans. Singlet oxygen quantum yield of erythrosine solutions was quantified using uric acid as a chemical-probe in an aqueous solution. The in vitro effect of the photodynamic antimicrobial activity of erythrosine in association with the halogen photopolimerizing light on Streptococcus mutans (UA 159) was assessed during one minute. Bacterial cultures treated with erythrosine alone served as negative control. Singlet oxygen with 24% and 2.8% degradation of uric acid in one minute and a quantum yield of 0.59 and 0.63 was obtained for the erythrosine samples illuminated with the halogen light and the LED array, respectively. The bacterial cultures with erythrosine illuminated with the halogen light presented a decreased number of CFU mL(-1) in comparison with the negative control, with minimal inhibitory concentrations between 0.312 and 0.156mgmL(-1). The photodynamic response of erythrosine induced by the halogen light was capable of killing S. mutans. Clinical trials should be conducted to better ascertain the use of erythrosine in association with halogen light source for the treatment of dental caries. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. A supramolecular miktoarm star polymer based on porphyrin metal complexation in water.

    PubMed

    Hou, Zhanyao; Dehaen, Wim; Lyskawa, Joël; Woisel, Patrice; Hoogenboom, Richard

    2017-07-25

    A novel supramolecular miktoarm star polymer was successfully constructed in water from a pyridine end-decorated polymer (Py-PmDEGA) and a metalloporphyrin based star polymer (ZnTPP-(PEG) 4 ) via metal-ligand coordination. The Py-PmDEGA moiety was prepared via a combination of reversible addition-fragmentation chain transfer polymerization (RAFT) and subsequent aminolysis and Michael addition reactions to introduce the pyridine end-group. The ZnTPP(PEG) 4 star-polymer was synthesized by the reaction between tetrakis(p-hydroxyphenyl)porphyrin and toluenesulfonyl-PEG, followed by insertion of a zinc ion into the porphyrin core. The formation of a well-defined supramolecular AB 4 -type miktoarm star polymer was unambiguously demonstrated via UV-Vis spectroscopic titration, isothermal titration calorimetry (ITC) and diffusion ordered NMR spectroscopy (DOSY).

  1. DESTRUCTION OF HALOGENATED HYDROCARBONS WITH SOLVATED ELECTRONS IN THE PRESENCE OF WATER. (R826180)

    EPA Science Inventory

    Model halogenated aromatic and aliphatic hydrocarbons and halogenated phenols were dehalogenated in seconds by solvated electrons generated from sodium in both anhydrous liquid ammonia and ammonia/water solutions. The minimum sodium required to completely dehalogenate these mo...

  2. Effects of Bulky Substituents of Push-Pull Porphyrins on Photovoltaic Properties of Dye-Sensitized Solar Cells.

    PubMed

    Higashino, Tomohiro; Kawamoto, Kyosuke; Sugiura, Kenichi; Fujimori, Yamato; Tsuji, Yukihiro; Kurotobi, Kei; Ito, Seigo; Imahori, Hiroshi

    2016-06-22

    To evaluate the effects of substituent bulkiness around a porphyrin core on the photovoltaic properties of porphyrin-sensitized solar cells, long alkoxy groups were introduced at the meso-phenyl group (ZnPBAT-o-C8) and the anchoring group (ZnPBAT-o-C8Cn, n = 4, 8) of an asymmetrically substituted push-pull porphyrin with double electron-donating diarylamino groups and a single electron-withdrawing carboxyphenylethynyl anchoring group. The spectroscopic and electrochemical properties of ZnPBAT-o-C8 and ZnPBAT-o-C8Cn were found to be superior to those of a push-pull porphyrin reference (YD2-o-C8), demonstrating their excellent light-harvesting and redox properties for dye-sensitized solar cells. A power conversion efficiency (η) of the ZnPBAT-o-C8-sensitized solar cell (η = 9.1%) is higher than that of the YD2-o-C8-sensitized solar cell (η = 8.6%) using iodine-based electrolyte due to the enhanced light-harvesting ability of ZnPBAT-o-C8. In contrast, the solar cells based on ZnPBAT-o-C8Cn, possessing the additional alkoxy chains in the anchoring group, revealed the lower η values of 7.3% (n = 4) and 7.0% (n = 8). Although ZnPBAT-o-C8Cn exhibited higher resistance at the TiO2-dye-electrolyte interface by virtue of the extra alkoxy chains, the reduced amount of the porphyrins on TiO2 by excessive addition of coadsorbent chenodeoxycholic acid (CDCA) for mitigating the aggregation on TiO2 resulted in the low η values. Meanwhile, the ZnPBAT-o-C8-sensitized solar cell showed the lower η value of 8.1% than the YD2-o-C8-sensitized solar cell (η = 9.8%) using cobalt-based electrolyte. The smaller η value of the ZnPBAT-o-C8-sensitized solar cell may be attributed to the insufficient blocking effect of the bulky substituents of ZnPBAT-o-C8 under the cobalt-based electrolyte conditions. Overall, the alkoxy chain length and substitution position around the porphyrin core are important factors to affect the cell performance.

  3. Visible light-driven O2 reduction by a porphyrin-laccase system.

    PubMed

    Lazarides, Theodore; Sazanovich, Igor V; Simaan, A Jalila; Kafentzi, Maria Chrisanthi; Delor, Milan; Mekmouche, Yasmina; Faure, Bruno; Réglier, Marius; Weinstein, Julia A; Coutsolelos, Athanassios G; Tron, Thierry

    2013-02-27

    Several recent studies have shown that the combination of photosensitizers with metalloenzymes can support a light-driven multielectron reduction of molecules such as CO(2) or HCN. Here we show that the association of the zinc tetramethylpyridinium porphyrin (ZnTMPyP(4+)) photosensitizer with the multicopper oxidase (MCO) laccase allows to link the oxidation of an organic molecule to the four electrons reduction of dioxygen into water. The enzyme is photoreduced within minutes with porphyrin/enzyme ratio as low as 1:40. With a 1:1 ratio, the dioxygen consumption rate is 1.7 μmol L(-1) s(-1). Flash photolysis experiments support the formation of the triplet excited state of ZnTMPyP(4+) which reduces the enzyme to form a radical cation of the porphyrin with a k(ET) ≈ 10(7) s(-1) M(-1). The long-lived triplet excited state of the ZnTMPyP(4+) (τ(0) = 0.72 ms) accounts for a substantial electron-transfer quantum yield, φ(ET) = 0.35. Consequently, the enzyme-dependent photo-oxidation of the electron donor occurs with a turnover of 8 min(-1) for the one-electron oxidation process, thereby supporting the suitability of such enzyme/sensitizer hybrid systems for aerobic photodriven transformations on substrates. This study is the first example of a phorphyrin-sensitized four-electron reduction of an enzyme of the MCO family, leading to photoreduction of dioxygen into water.

  4. Application-oriented computational studies on a series of D-π-A structured porphyrin sensitizers with different electron-donor groups.

    PubMed

    Fan, Chencheng; Zhang, Bao; Li, Yuanchao; Liang, Yuxia; Xue, Xiaodong; Feng, Yaqing

    2015-11-11

    A series of D-π-A zinc porphyrin sensitizers bearing a substituted iminodibenzyl group at the porphyrin meso position, which is expected to have different electron-donating abilities, were designed. Theoretical studies were performed to examine the photovoltaic properties of these molecules in dye-sensitized solar cells (DSSCs). In particular, the important concepts, the Fukui function and the extended condensed Fukui function, are employed to describe the electron-donating abilities accurately at the quantitative level. Tangui Le Bahers model was adopted to analyze charge transfer (CT) during electron transition. A correlation between the electron donating abilities of the derived iminodibenzyl group and CT was built to evaluate the cell performance based on sensitizers . The theoretical studies showed that porphyrins bearing an extremely strong electron-donating group (EDG) would fail in the generation of photocurrent in the closed circuit when applied in DSSCs due to the higher level of the HOMO energy than the redox potential of the redox couple (I(-)/I3(-)). The one with a weaker EDG () is expected to show better photovoltaic performance than porphyrin with an unsubstituted iminodibenzyl group. This study demonstrates a reliable method involving the employment of the Fukui function, the extended condensed Fukui function and the Tangui Le Bahers model for the evaluation of newly designed D-π-A type porphyrin sensitizers for use in DSSCs, and as guidance for future molecular design.

  5. GUN4-Porphyrin Complexes Bind the ChlH/GUN5 Subunit of Mg-Chelatase and Promote Chlorophyll Biosynthesis in Arabidopsis[W

    PubMed Central

    Adhikari, Neil D.; Froehlich, John E.; Strand, Deserah D.; Buck, Stephanie M.; Kramer, David M.; Larkin, Robert M.

    2011-01-01

    The GENOMES UNCOUPLED4 (GUN4) protein stimulates chlorophyll biosynthesis by activating Mg-chelatase, the enzyme that commits protoporphyrin IX to chlorophyll biosynthesis. This stimulation depends on GUN4 binding the ChlH subunit of Mg-chelatase and the porphyrin substrate and product of Mg-chelatase. After binding porphyrins, GUN4 associates more stably with chloroplast membranes and was proposed to promote interactions between ChlH and chloroplast membranes—the site of Mg-chelatase activity. GUN4 was also proposed to attenuate the production of reactive oxygen species (ROS) by binding and shielding light-exposed porphyrins from collisions with O2. To test these proposals, we first engineered Arabidopsis thaliana plants that express only porphyrin binding–deficient forms of GUN4. Using these transgenic plants and particular mutants, we found that the porphyrin binding activity of GUN4 and Mg-chelatase contribute to the accumulation of chlorophyll, GUN4, and Mg-chelatase subunits. Also, we found that the porphyrin binding activity of GUN4 and Mg-chelatase affect the associations of GUN4 and ChlH with chloroplast membranes and have various effects on the expression of ROS-inducible genes. Based on our findings, we conclude that ChlH and GUN4 use distinct mechanisms to associate with chloroplast membranes and that mutant alleles of GUN4 and Mg-chelatase genes cause sensitivity to intense light by a mechanism that is potentially complex. PMID:21467578

  6. Temperature-Dependent Conformations of a Membrane Supported ‘Zinc Porphyrin Tweezer’ by 2D Fluorescence Spectroscopy

    PubMed Central

    Widom, Julia R.; Lee, Wonbae; Perdomo-Ortiz, Alejandro; Rappoport, Dmitrij; Molinski, Tadeusz F.; Aspuru-Guzik, Alán; Marcus, Andrew H.

    2013-01-01

    We studied the equilibrium conformations of a ‘zinc porphyrin tweezer’ composed of two carboxylphenyl-functionalized zinc tetraphenyl porphyrin subunits connected by a 1,4 butyndiol spacer, which was suspended inside the amphiphilic regions of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) liposomes. By combining phase-modulation two-dimensional fluorescence spectroscopy (2D FS) with linear absorbance and fluorimetry, we determined that the zinc porphyrin tweezer adopts a mixture of ‘folded’ and ‘extended’ conformations in the membrane. By fitting an exciton-coupling model to a series of data sets recorded over a range of temperatures (17 – 85 °C) and at different laser center wavelengths, we determined that the folded form of the tweezer is stabilized by a favorable change in the entropy of the local membrane environment. Our results provide insights toward understanding the balance of thermodynamic factors that govern molecular assembly in membranes. PMID:23480874

  7. Halogen Bonding versus Hydrogen Bonding: A Molecular Orbital Perspective

    PubMed Central

    Wolters, Lando P; Bickelhaupt, F Matthias

    2012-01-01

    We have carried out extensive computational analyses of the structure and bonding mechanism in trihalides DX⋅⋅⋅A− and the analogous hydrogen-bonded complexes DH⋅⋅⋅A− (D, X, A=F, Cl, Br, I) using relativistic density functional theory (DFT) at zeroth-order regular approximation ZORA-BP86/TZ2P. One purpose was to obtain a set of consistent data from which reliable trends in structure and stability can be inferred over a large range of systems. The main objective was to achieve a detailed understanding of the nature of halogen bonds, how they resemble, and also how they differ from, the better understood hydrogen bonds. Thus, we present an accurate physical model of the halogen bond based on quantitative Kohn–Sham molecular orbital (MO) theory, energy decomposition analyses (EDA) and Voronoi deformation density (VDD) analyses of the charge distribution. It appears that the halogen bond in DX⋅⋅⋅A− arises not only from classical electrostatic attraction but also receives substantial stabilization from HOMO–LUMO interactions between the lone pair of A− and the σ* orbital of D–X. PMID:24551497

  8. ALA-based fluorescent diagnosis of malignant oral lesions in the presence of bacterial porphyrin formation

    NASA Astrophysics Data System (ADS)

    Schleier, P.; Berndt, A.; Zinner, K.; Zenk, W.; Dietel, W.; Pfister, W.

    2006-02-01

    The aminolevulinic acid (5-ALA) -based fluorescence diagnosis has been found to be promising for an early detection and demarcation of superficial oral squamous cell carcinomas (OSCC). This method has previously demonstrated high sensitivity, however this clinical trial showed a specificity of approximately 62 %. This specificity was mainly restricted by tumor detection in the oral cavity in the presence of bacteria. After topical ALA application in the mouth of patients with previously diagnosed OSSC, red fluorescent areas were observed which did not correlate to confirm histological findings. Swabs and plaque samples were taken from 44 patients and cultivated microbiologically. Fluorescence was investigated (OMA-system) from 32 different bacteria strains found naturally in the oral cavity. After ALA incubation, 30 of 32 strains were found to synthesize fluorescent porphyrins, mainly Protoporphyrin IX. Also multiple fluorescent spectra were obtained having peak wavelengths of 636 nm and around 618 nm - 620 nm indicating synthesis of different porphyrins, such as the lipophylic Protoporphyrin IX (PpIX) and hydrophylic porphyrins (water soluble porphyrins, wsp). Of the 32 fluorescent bacterial strains, 18 produced wsp, often in combination with PpIX, and 5 produced solely wsp. These results clarify that ALA-based fluorescence diagnosis without consideration or suppression of bacteria fluorescence may lead to false-positive findings. It is necessary to suppress bacteria fluorescence with suitable antiseptics before starting the procedure. In this study, when specific antiseptic pre-treatment was performed bacterial associated fluorescence was significantly reduced.

  9. Chiroptical properties of an alternatingly functionalized cellotriose bearing two porphyrin groups

    USDA-ARS?s Scientific Manuscript database

    Alternatingly functionalized cellulose molecules have potential applications in optoelectronics and molecular receptors. For example, cellulose-based solar cells have been proposed. As a prototype for such molecules, the trisaccharide fragment of cellulose was modified by attachment of porphyrin gro...

  10. 40 CFR 721.535 - Halogenated alkane (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Section 721.535 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.535 Halogenated alkane (generic). (a) Chemical substance and significant new uses subject to...

  11. Unique Diagnostic and Therapeutic Roles of Porphyrins and Phthalocyanines in Photodynamic Therapy, Imaging and Theranostics

    PubMed Central

    Josefsen, Leanne B.; Boyle, Ross W.

    2012-01-01

    Porphyrinic molecules have a unique theranostic role in disease therapy; they have been used to image, detect and treat different forms of diseased tissue including age-related macular degeneration and a number of different cancer types. Current focus is on the clinical imaging of tumour tissue; targeted delivery of photosensitisers and the potential of photosensitisers in multimodal biomedical theranostic nanoplatforms. The roles of porphyrinic molecules in imaging and pdt, along with research into improving their selective uptake in diseased tissue and their utility in theranostic applications are highlighted in this Review. PMID:23082103

  12. Synthesis, reactivity, and properties of N-fused porphyrin rhenium(I) tricarbonyl complexes.

    PubMed

    Toganoh, Motoki; Ikeda, Shinya; Furuta, Hiroyuki

    2007-11-12

    The thermal reactions of N-fused tetraarylporphyrins or N-confused tetraarylporphyrins with Re2(CO)10 gave the rhenium(I) tricarbonyl complexes bearing N-fused porphyrinato ligands (4) in moderate to good yields. The rhenium complexes 4 are characterized by mass, IR, 1H, and 13C NMR spectroscopy, and the structures of tetraphenylporphynato complex 4a and its nitro derivative 15 are determined by X-ray single crystal analysis. The rhenium complexes 4 show excellent stability against heat, light, acids, bases, and oxidants. The aromatic substitution reactions of 4 proceed without a loss of the center metal to give the nitro (15), formyl (16), benzoyl (17), and cyano derivatives (19), regioselectively. In the electrochemical measurements for 4, one reversible oxidation wave and two reversible reduction waves are observed. Their redox potentials imply narrow HOMO-LUMO band gaps of 4 and are consistent with their electronic absorption spectra, in which the absorption edges exceed 1000 nm. Theoretical study reveals that the HOMO and LUMO of the rhenium complexes are exclusively composed of the N-fused porphyrin skeleton. Protonation of 4 takes place at the 21-position regioselectively, reflecting the high coefficient of the C21 atom in the HOMO orbital. The skeletal rearrangement reaction from N-confused porphyrin Re(I) complex (8) to N-fused porphyrin Re(I) complex (4) is suggested from the mechanistic study as well as DFT calculations.

  13. Asymmetric Cationic Porphyrin as a New G-Quadruplex Probe with Wash-Free Cancer-Targeted Imaging Ability Under Acidic Microenvironments.

    PubMed

    Zhang, Ran; Cheng, Meng; Zhang, Li-Ming; Zhu, Li-Na; Kong, De-Ming

    2018-04-25

    Porphyrins are promising candidates for nucleic acid G-quadruplex-specific optical recognition. We previously demonstrated that G-quadruplex recognition specificity of porphyrins could be improved by introducing bulky side arm substituents, but the enhanced protonation tendency limits their applications in some cases, such as under acidic conditions. Here, we demonstrated that the protonation tendency of porphyrin derivatives could be efficiently overcome by increasing molecular asymmetry. To validate this, an asymmetric, water-soluble, cationic porphyrin FA-TMPipEOPP (5-{4-[2-[[(2 E)-3-[3-methoxy-4-[2-(1-methyl-1-piperidinyl)ethoxy]phenyl]-1-oxo-2-propenyl]oxy]ethoxy]phenyl},10,15,20-tri{4-[2-(1-methyl-1-piperidinyl)ethoxy]-phenyl}porphyrin) was synthesized by introducing a ferulic acid (FA) unit at one side arm, and its structure was well-characterized. Unlike its symmetric counterpart TMPipEOPP that has a tendency to protonate under acidic conditions, FA-TMPipEOPP remained in the unprotonated monomeric form under the pH range of 2.0-8.0. Correspondingly, FA-TMPipEOPP showed better G-quadruplex recognition specificity than TMPipEOPP and thus might be used as a specific optical probe for colorimetric and fluorescent recognition of G-quadruplexes under acidic conditions. The feasibility was demonstrated by two proof-of-concept studies: probing structural competition between G-quadruplexes and duplexes and label-free and wash-free cancer cell-targeted bioimaging under an acidic tumor microenvironment. As G-quadruplex optical probes, FA-TMPipEOPP works well under acidic conditions, whereas TMPipEOPP works well under neutral conditions. This finding provides useful information for G-quadruplex probe research. That is, porphyrin-based G-quadruplex probes suitable for different pH conditions might be obtained by adjusting the molecular symmetry.

  14. Methods and intermediates for the synthesis of dipyrrin-substituted porphyrinic macrocycles

    DOEpatents

    Yu, Lianhe; Muthukumaran, Kannan; Sreedharan, Prathapan; Lindsey, Jonathan S.

    2010-05-25

    The present invention provides dipyrrin substituted porphyrinic macrocycles, intermediates useful for making the same, and methods of making the same. Such compounds may be used for purposes including the making of molecular memory devices, solar cells and light harvesting arrays.

  15. Chemical Action of Halogenated Agents in Fire Extinguishing

    NASA Technical Reports Server (NTRS)

    Belles, Frank E.

    1955-01-01

    The action of halogenated agents in preventing flame propagation in fuel-air mixtures in laboratory tests is discussed in terms of a possible chemical mechanism. The mechanism chosen is that of chain-breaking reactions between agent and active particles (hydrogen and oxygen atoms and hydroxyl radicsls). Data from the literature on the flammability peaks of n-heptane agent-air mixtures are treated. Ratings of agent effectiveness in terms of the fuel equivalent of the agent, based on both fuel and agent concentrations at the peak, are proposed as preferable to ratings in terms of agent concentration alone. These fuel-equivalent ratings are roughly correlated by reactivities assigned to halogen and hydrogen atoms in the agent molecules. It is concluded that the presence of hydrogen in agent need not reduce its fire-fighting ability, provided there is enough halogen to make the agent nonflammable. A method is presented for estimating from quenching-distance data a rate constant for the reaction of agent with active particles. A quantitative result is obtained for methyl bromide. This rate constant predicts the observed peak concentration of methyl bromide quite well. However, more data are needed to prove the validity of the method. The assumption that hal.ogenatedagents act mainly by chain-bresking reactions with active particles is consistent with the experimental facts and should help guide the selection of agents for further tests.

  16. Energetics of halogen impurities in thorium dioxide

    NASA Astrophysics Data System (ADS)

    Kuganathan, Navaratnarajah; Ghosh, Partha S.; Arya, Ashok K.; Dey, Gautam K.; Grimes, Robin W.

    2017-11-01

    Defect energies for halogen impurity atoms (Cl, Br and I) in thoria are calculated using the generalized gradient approximation and projector augmented plane wave potentials under the framework of density functional theory. The energy to place a halogen atom at a pre-existing lattice site is the incorporation energy. Seven sites are considered: octahedral interstitial, O vacancy, Th vacancy, Th-O di-vacancy cluster (DV) and the three O-Th-O tri-vacancy cluster (NTV) configurations. For point defects and vacancy clusters, neutral and all possible defect charge states up to full formal charge are considered. The most favourable incorporation site for Cl is the singly charged positive oxygen vacancy while for Br and I it is the NTV1 cluster. By considering the energy to form the defect sites, solution energies are generated. These show that in both ThO2-x and ThO2 the most favourable solution equilibrium site for halides is the single positively charged oxygen vacancy (although in ThO2, I demonstrates the same solubility in the NTV1 and DV clusters). Solution energies are much lower in ThO2-x than in ThO2 indicating that stoichiometry is a significant factor in determining solubility. In ThO2, all three halogens are highly insoluble and in ThO2-x Br and I remain insoluble. Although ½Cl2 is soluble in ThO2-x alternative phases such as ZrCl4 exist which are of lower energy.

  17. On the ultrafast charge migration and subsequent charge directed reactivity in Cl⋯N halogen-bonded clusters following vertical ionization

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chandra, Sankhabrata; Bhattacharya, Atanu, E-mail: atanub@ipc.iisc.ernet.in; Periyasamy, Ganga

    2015-06-28

    In this article, we have presented ultrafast charge transfer dynamics through halogen bonds following vertical ionization of representative halogen bonded clusters. Subsequent hole directed reactivity of the radical cations of halogen bonded clusters is also discussed. Furthermore, we have examined effect of the halogen bond strength on the electron-electron correlation- and relaxation-driven charge migration in halogen bonded complexes. For this study, we have selected A-Cl (A represents F, OH, CN, NH{sub 2}, CF{sub 3}, and COOH substituents) molecules paired with NH{sub 3} (referred as ACl:NH{sub 3} complex): these complexes exhibit halogen bonds. To the best of our knowledge, this ismore » the first report on purely electron correlation- and relaxation-driven ultrafast (attosecond) charge migration dynamics through halogen bonds. Both density functional theory and complete active space self-consistent field theory with 6-31 + G(d, p) basis set are employed for this work. Upon vertical ionization of NCCl⋯NH{sub 3} complex, the hole is predicted to migrate from the NH{sub 3}-end to the ClCN-end of the NCCl⋯NH{sub 3} complex in approximately 0.5 fs on the D{sub 0} cationic surface. This hole migration leads to structural rearrangement of the halogen bonded complex, yielding hydrogen bonding interaction stronger than the halogen bonding interaction on the same cationic surface. Other halogen bonded complexes, such as H{sub 2}NCl:NH{sub 3}, F{sub 3}CCl:NH{sub 3}, and HOOCCl:NH{sub 3}, exhibit similar charge migration following vertical ionization. On the contrary, FCl:NH{sub 3} and HOCl:NH{sub 3} complexes do not exhibit any charge migration following vertical ionization to the D{sub 0} cation state, pointing to interesting halogen bond strength-dependent charge migration.« less

  18. Hydrogen bond controlled adduct formation of meso-tetra(4-sulfonatophenyl)porphyrin with protic acids: a UV-vis spectroscopic study.

    PubMed

    Zakavi, Saeed; Rahiminezhad, Hajar; Alizadeh, Robabeh

    2010-12-01

    Interaction of meso-tetra(4-sulfonatophenyl)porphyrin (H2tppS4) with weak and strong protic acid have been studied by UV-vis spectroscopy in water, dichloromethane and methanol. Different shifts of the Soret and Q(0,0) bands in the three solvents, the aggregation of diprotonated species and the stability of porphyrin-acid adducts in the solution, may be explained by the inter- and intramolecular hydrogen bonds. Whilst, the addition of excess amounts of tetra-n-butylammonium chloride to H2tppS4(Cl)2 in dichloromethane has little to no effect on the UV-vis spectrum of the dication, gradual addition of tetra-n-butylammonium hydrogen sulfate to the dichloromethane solution of H2tppS4(H2SO4)2 leads to the degradation of adducts and the release of porphryin. The results of this study clearly show the crucial role played by hydrogen bonds between the porphyrin diprotonated species and the counter ion in the stability of porphyrin diacids in solution. Copyright © 2010 Elsevier B.V. All rights reserved.

  19. Formation of halogenated acetones in the lower troposphere

    NASA Astrophysics Data System (ADS)

    Sattler, Tobias; Wittmer, Julian; Krause, Torsten; Schöler, Heinz Friedrich; Kamilli, Katharina; Held, Andreas; Zetzsch, Cornelius; Ofner, Johannes; Atlas, Elliot

    2015-04-01

    Western Australia is a semi-/arid region that is heavily influenced by climate change and agricultural land use. The area is known for its saline lakes with a wide range of hydrogeochemical parameters and consists of ephemeral saline and saline groundwater fed lakes with a pH range from 2.5 to 7.1. In 2012 a novel PTFE-chamber was setup directly on the lakes. The 1.5 m³ cubic chamber was made of UV transparent PTFE foil to permit photochemistry while preventing dilution of the air due to lateral wind transport. This experimental setup allows linking measured data directly to the chemistry of and above the salt lakes. Air samples were taken using stainless steel canisters and measured by GC-MS/ECD. Sediment, crust and water samples were taken for investigation of potential VOC and VOX emissions in the laboratory using GC-MS. Several lakes were investigated and canister samples were taken over the day to see diurnal variations. The first samples were collected at 6 a.m. and from this time every 2 hours a canister was filled with chamber air. Concentrations of chloroacetone up to 15 ppb and of bromoacetone up to 40 ppb in the air samples were detected. The concentrations vary over the day and display their highest values around noon. Soil and water samples showed a variety of highly volatile and semi-volatile VOC/VOX but no halogenated acetones. An abiotic formation of these VOC/VOX seems conclusive due to iron-catalysed reactions below the salt crust [1]. The salt crust is the interface through which VOC/VOX pass from soil/groundwater to the atmosphere where they were photochemically altered. This explains the finding of halo acetones only in the air samples and not in water and soil samples measured in the laboratory. The main forming pathway for these haloacetones is the direct halogenation due to atomic chlorine and bromine above the salt lakes [2]. A minor pathway is the atmospheric degradation of chloropropane and bromopropane [3]. These halopropanes were found

  20. Reconciliation of Halogen-Induced Ozone Loss with the Total-Column Ozone Record

    NASA Technical Reports Server (NTRS)

    Shepherd, T. G.; Plummer, D. A.; Scinocca, J. F.; Hegglin, M. I.; Fioletov, V. E.; Reader, M. C.; Remsberg, E.; von Clarmann, T.; Wang, H. J.

    2014-01-01

    The observed depletion of the ozone layer from the 1980s onwards is attributed to halogen source gases emitted by human activities. However, the precision of this attribution is complicated by year-to-year variations in meteorology, that is, dynamical variability, and by changes in tropospheric ozone concentrations. As such, key aspects of the total-column ozone record, which combines changes in both tropospheric and stratospheric ozone, remain unexplained, such as the apparent absence of a decline in total-column ozone levels before 1980, and of any long-term decline in total-column ozone levels in the tropics. Here we use a chemistry-climate model to estimate changes in halogen-induced ozone loss between 1960 and 2010; the model is constrained by observed meteorology to remove the eects of dynamical variability, and driven by emissions of tropospheric ozone precursors to separate out changes in tropospheric ozone. We show that halogen-induced ozone loss closely followed stratospheric halogen loading over the studied period. Pronounced enhancements in ozone loss were apparent in both hemispheres following the volcanic eruptions of El Chichon and, in particular, Mount Pinatubo, which significantly enhanced stratospheric aerosol loads. We further show that approximately 40% of the long-term non-volcanic ozone loss occurred before 1980, and that long-term ozone loss also occurred in the tropical stratosphere. Finally, we show that halogeninduced ozone loss has declined by over 10% since stratospheric halogen loading peaked in the late 1990s, indicating that the recovery of the ozone layer is well underway.

  1. Cationic Zn-Porphyrin Polymer Coated onto CNTs as a Cooperative Catalyst for the Synthesis of Cyclic Carbonates.

    PubMed

    Jayakumar, Sanjeevi; Li, He; Chen, Jian; Yang, Qihua

    2018-01-24

    The development of solid catalysts containing multiple active sites that work cooperatively is very attractive for biomimetic catalysis. Herein, we report the synthesis of bifunctional catalysts by supporting cationic porphyrin-based polymers on carbon nanotubes (CNTs) using the direct reaction of 5,10,15,20-tetrakis(4-pyridyl)porphyrin zinc(II), di(1H-imidazol-1-yl)methane, and 1,4-bis(bromomethyl)benzene in the presence of CNTs. The bifunctional catalysts could efficiently catalyze the cycloaddition reaction of epoxides and CO 2 under solvent-free conditions with porphyrin zinc(II) as the Lewis acid site and a bromine anion as a nucleophilic agent working in a cooperative way. Furthermore, a relative amount of porphyrin zinc(II) and quaternary ammonium bromide could be facilely adjusted for facilitating cooperative behavior. The bifunctional catalyst with a TOF up to 2602 h -1 is much more active than the corresponding homogeneous counterpart and is one of the most active heterogeneous catalysts ever reported under cocatalyst-free conditions. The high activity is mainly attributed to the enhanced cooperation effect of the bifunctional catalyst. With a wide substrate scope, the bifunctional catalyst could be stably recycled. This work demonstrates a new approach for the generation of a cooperative activation effect for solid catalysts.

  2. Charge Carrier Dynamics and pH Effect on Optical Properties of Anionic and Cationic Porphyrin-Graphene Oxide Composites

    NASA Astrophysics Data System (ADS)

    Bajjou, O.; Bakour, A.; Khenfouch, M.; Baitoul, M.; Mothudi, B.; Maaza, M.; Faulques, E.

    2018-02-01

    Composites of graphene oxide (GO) functionalized with Sn(V) tetrakis (4-pyridyl)porphyrin (SnTPyP2+) and meso-tetrakis(4-phenylsulfonic acid)porphyrin (H4TPPS4 2- ) were prepared at different pH values.Successful synthesis of water-soluble stable suspension of GO-SnTPyP2+ and GO-H4TPPS4 2-was confirmed using various spectroscopic techniques, including scanning electronic microscopy (SEM), Raman spectroscopy, and ultraviolet-visible (UV-Vis) absorption. Variation of the pH was found to strongly influence the optical properties of the GO-SnTPyP2+ and GO-H4TPPS4 2-composites, as demonstrated by the UV-Vis absorption results. Steady-state photoluminescence (PL) and time-resolved PL (TRPL) results for both composites showed PL quenching and decrease in the exciton mean lifetime, suggesting strong excited-state interactions between the different components. Moreover, charge carrier dynamics study revealed that insertion of GO into both porphyrin derivatives led to faster mean lifetime for excitons with a slight advantage in the case of the cationic porphyrin-GO composite, making it a better choice for charge separation applications thanks to the higher efficiency of charge/energy transfer interactions.

  3. Comparison between the electrocatalytic properties of different metal ion phthalocyanines and porphyrins towards the oxidation of hydroxide.

    PubMed

    De Wael, Karolien; Adriaens, Annemie

    2008-02-15

    This work reports on the electrocatalytic oxidation of hydroxide using different central metal ion phthalocyanines and porphyrins immobilized on gold electrodes. The apparent electrocatalytic activity of cobalt phthalocyanine or porphyrin modified electrodes was found to be the greatest among the present series of metal ion macrocycles investigated. Copper and unmetallated phthalocyanine or porphyrin modified electrodes show no electrocatalytic behaviour towards hydroxide, such as bare gold. A possible mechanism for the enhanced reactivity of cobalt ion macrocycles towards the oxygen evolution is given. It is also stated that the electrocatalytic activity towards an adsorbate involves several aspects, such as the coordination state of the central metal ion, the nature of the ligand, the stability of the complexes, the number of d electrons, the energy of orbitals and the strength of the bonding between the central metal ion and the axial ligand.

  4. Sources of halogens in the environment, influences on human and animal health.

    PubMed

    Fuge, R

    1988-06-01

    Of the halogens, fluorine has the highest crustal abundance (544 mg/kg) while iodine has the lowest (0.25 mg/kg), however, chlorine is by far the most abundant halogen in the cosmos. The geochemistries of the four naturally occurring halogens have some similarities with fluorine, chlorine and bromine being classified as lithophile elements while iodine is more chalcophile in nature. Bromine and iodine behave in a similar fashion in the secondary environment and could be classified as biophile elements being concentrated in organic matter. Chlorine, bromine and iodine are strongly enriched in the sea while iodine and to a lesser extent bromine are further concentrated in the marine algae.Apart from the occurrence of fluorine in fluorite (CaF2) there are few commonly occurring minerals which contain the halogens as essential constituents. In the igneous environment fluorine and chlorine tend to occupy hydroxyl lattice sites in micas, amphiboles, apatites etc., while in sediments clays can contain appreciable quantities of these elements. Bromine and iodine, however, would be unlikely to fit into the lattice sites of common rock-forming minerals.Bromine, like iodine, is probably volatilised from the marine environment and is carried on to land surfaces. This behaviour of iodine and bromine is reflected in the increased I/CI and Br/CI ratios of surface run-off in continental compared with near coastal environments.Limited information on the soil geochemistry of the halogens suggests that the soil contents of chlorine, bromine and iodine are influenced by proximity to the sea. Soil fluorine, however, is generally dependent on its content in the parent material. In some areas pollutant sources of the halogens contribute appreciably to their concentration in the environment.Iodine and chlorine are essential elements for mammals and fluorine has been shown to have beneficial effects on bone and tooth formation. However, excess quantities of dietary fluorine can be harmful

  5. Mouse Model of Halogenated Platinum Salt Hypersensitivity

    EPA Science Inventory

    Occupational exposure to halogenated platinum salts can trigger the development of asthma. Concern for increased asthma risk exists for the general population due to the use of platinum (Pt) in catalytic converters and its emerging use as a diesel fuel additive. To investigate a...

  6. Technology for radiation efficiency measurement of high-power halogen tungsten lamp used in calibration of high-energy laser energy meter.

    PubMed

    Wei, Ji Feng; Hu, Xiao Yang; Sun, Li Qun; Zhang, Kai; Chang, Yan

    2015-03-20

    The calibration method using a high-power halogen tungsten lamp as a calibration source has many advantages such as strong equivalence and high power, so it is very fit for the calibration of high-energy laser energy meters. However, high-power halogen tungsten lamps after power-off still reserve much residual energy and continually radiate energy, which is difficult to be measured. Two measuring systems were found to solve the problems. One system is composed of an integrating sphere and two optical spectrometers, which can accurately characterize the radiative spectra and power-time variation of the halogen tungsten lamp. This measuring system was then calibrated using a normal halogen tungsten lamp made of the same material as the high-power halogen tungsten lamp. In this way, the radiation efficiency of the halogen tungsten lamp after power-off can be quantitatively measured. In the other measuring system, a wide-spectrum power meter was installed far away from the halogen tungsten lamp; thus, the lamp can be regarded as a point light source. The radiation efficiency of residual energy from the halogen tungsten lamp was computed on the basis of geometrical relations. The results show that the halogen tungsten lamp's radiation efficiency was improved with power-on time but did not change under constant power-on time/energy. All the tested halogen tungsten lamps reached 89.3% of radiation efficiency at 50 s after power-on. After power-off, the residual energy in the halogen tungsten lamp gradually dropped to less than 10% of the initial radiation power, and the radiation efficiency changed with time. The final total radiation energy was decided by the halogen tungsten lamp's radiation efficiency, the radiation efficiency of residual energy, and the total power consumption. The measuring uncertainty of total radiation energy was 2.4% (here, the confidence factor is two).

  7. Decomposition of energetic chemicals contaminated with iron or stainless steel.

    PubMed

    Chervin, Sima; Bodman, Glenn T; Barnhart, Richard W

    2006-03-17

    Contamination of chemicals or reaction mixtures with iron or stainless steel is likely to take place during chemical processing. If energetic and thermally unstable chemicals are involved in a manufacturing process, contamination with iron or stainless steel can impact the decomposition characteristics of these chemicals and, subsequently, the safety of the processes, and should be investigated. The goal of this project was to undertake a systematic approach to study the impact of iron or stainless steel contamination on the decomposition characteristics of different chemical classes. Differential scanning calorimetry (DSC) was used to study the decomposition reaction by testing each chemical pure, and in mixtures with iron and stainless steel. The following classes of energetic chemicals were investigated: nitrobenzenes, tetrazoles, hydrazines, hydroxylamines and oximes, sulfonic acid derivatives and monomers. The following non-energetic groups were investigated for contributing effects: halogens, hydroxyls, amines, amides, nitriles, sulfonic acid esters, carbonyl halides and salts of hydrochloric acid. Based on the results obtained, conclusions were drawn regarding the sensitivity of the decomposition reaction to contamination with iron and stainless steel for the chemical classes listed above. It was demonstrated that the most sensitive classes are hydrazines and hydroxylamines/oximes. Contamination of these chemicals with iron or stainless steel not only destabilizes them, leading to decomposition at significantly lower temperatures, but also sometimes causes increased severity of the decomposition. The sensitivity of nitrobenzenes to contamination with iron or stainless steel depended upon the presence of other contributing groups: the presence of such groups as acid chlorides or chlorine/fluorine significantly increased the effect of contamination on decomposition characteristics of nitrobenzenes. The decomposition of sulfonic acid derivatives and tetrazoles

  8. Inorganic Halogen Oxidizer Research

    DTIC Science & Technology

    1981-04-21

    International Rocketdyne Division 6633 Canoga Avenue Canoga Park, California 91304 RI/R.D8l1-14O A ’N-NUAL REPORT INORGANIC HALOGEN OXIDIZER RESEARCH (I...March 1980 through 8 February 198L) 21 April 1981 "Contract N00014-79-C-0176 . GO. 95067 . , Office of Naval Research I-- Power Branch , ,, Code 473...Office of Naval Research Power Branch 11 I-ar Ccovie 473 ~ UMBER OF PA’E1 Arlington. VA 22217 . 76" 74 AONIYONING AGENCY NAME III Dw~S~ d, I f,. .f

  9. Endogenous and exogenous porphyrins as photosensitizers in the Hep-2 human carcinoma cell line.

    PubMed

    Alvarez, M G; Milanesio, M; Rivarola, V; Durantini, E; Batlle, A; Fukuda, H

    2009-07-01

    The photodynamic activity of three photosensitizers (PS): AL-induced PPIX, the porphyrin derivative 5-(4-trimethylammoniumphenyl)-10, 5, 20-tris (2,4,6- trimethoxyphenyl) porphyrin (CP) and the molecular dyad porphyrin-C(60) (P-C(60)), the last two incorporated into liposomal vesicles, was evaluated on Hep-2 human larynx carcinoma cell line. ALA-induced accumulation of the endogenous PS PPIX, reached saturation values between 5 and 24 h incubation time; the maximal PPIX content was 5.7 nmol/106 cells. The same intracellular level was accumulated when the cationic porphyrin CP was used, while the amount of P-C(60) attained was 1.5 nmol/106 cells. Under violet-blue exciting light, the fluorescence of PPIX and P-C(60) was found in the cytoplasm showing a granular appearance indicating lysosomal localization. CP was mainly detected as a filamentous pattern characteristic of mitochondrial localization. No dark cytotoxicity was observed using 1mM ALA, 5 microM CP and 1 microM P-C(60) after 24 h incubation. Cell morphology was analyzed using Hoechst-33258, toluidine blue staining, TUNEL assay and DNA fragmentation, 24 h after irradiation with 54 J/cm2. When photosensitized with ALA and P-C(60), chromatine condensation characteristic of apoptotic cell death was found; instead, 58 % of necrotic cells were observed with CP. The results show that in the Hep-2 cells, of the three PS analyzed, the molecular dyad P-C(60) was more efficient than CP and PPIX, and confirm that PDT can induce different mechanisms of cell death depending on the PS and the irradiation dose.

  10. Halogens and the Chemistry of the Free Troposphere

    NASA Technical Reports Server (NTRS)

    Lary, David John

    2004-01-01

    The role of halogens in both the marine boundary layer and the stratosphere has long been recognized, while their role in the free troposphere is often not considered in global chemical models. However, a careful examination of free-tropospheric chemistry constrained by observations using a full chemical data assimilation system shows that halogens do play a significant role in the free troposphere. In particular, the chlorine initiation of methane oxidation in the free troposphere can contribute more than 10%, and in some regions up to 50%, of the total rate of initiation. The initiation of methane oxidation by chlorine is particularly important below the polar vortex and in northern mid-latitudes. Likewise, the hydrolysis of BrONO2 alone can contribute more than 35% of the HNO3 production rate in the free-troposphere.

  11. Porphyrin-Embedded Silicate Materials for Detection of Hydrocarbon Solvents

    DTIC Science & Technology

    2011-01-14

    Sensors 2011, 11, 886-904; doi:10.3390/s110100886 sensors ISSN 1424-8220 www.mdpi.com/journal/ sensors Article Porphyrin-Embedded Silicate...Prescribed by ANSI Std Z39-18 Sensors 2011, 11 887 1. Introduction Mesoporous silicates have been widely described in sensing...absorption spectroscopy, quartz crystal microbalance ( QCM ), and FTIR have been utilized for aromatic hydrocarbon sensing applications based on these

  12. Auger analysis of films formed on metals in sliding contact with halogenated polymers

    NASA Technical Reports Server (NTRS)

    Pepper, S. V.

    1974-01-01

    The use of Auger electron spectroscopy (AES) to search for transferred polymer must contend with the fact that there has been no published work on Auger analysis of polymers. Since this is a new area for AES, the Auger spectra of polymers and of halogenated polymers in particular is discussed. It is shown that the Auger spectra of halogenated polymers have certain characteristics that permit an assessment of whether a polymeric transfer film has been established by sliding contact. The discussion is general and the concepts should be useful in considering the Auger analysis of any polymer. The polymers chosen for this study are the halogenated polymers polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), and polychlorotrifluorethylene (PCTFE).

  13. Engendering Long-Term Air and Light Stability of a TiO2-Supported Porphyrinic Dye via Atomic Layer Deposition.

    PubMed

    Hoffeditz, William L; Son, Ho-Jin; Pellin, Michael J; Farha, Omar K; Hupp, Joseph T

    2016-12-21

    Organic and porphyrin-based chromophores are prevalent in liquid-junction photovoltaic and photocatalytic solar-cell chemistry; however, their long-term air and light instability may limit their practicality in real world technologies. Here, we describe the protection of a zinc porphyrin dye, adsorbed on nanoparticulate TiO 2 , from air and light degradation by a protective coating of alumina grown with a previously developed post-treatment atomic layer deposition (ALD) technique. The protective Al 2 O 3 ALD layer is deposited using dimethylaluminum isopropoxide as an Al source; in contrast to the ubiquitous ALD precursor trimethylaluminum, dimethylaluminum isopropoxide does not degrade the zinc porphyrin dye, as confirmed by UV-vis measurements. The growth of this protective ALD layer around the dye can be monitored by an in-reactor quartz crystal microbalance (QCM). Furthermore, greater than 80% of porphyrin light absorption is retained over ∼1 month of exposure to air and light when the protective coating is present, whereas almost complete loss of porphyrin absorption is observed in less than 2 days in the absence of the ALD protective layer. Applying the Al 2 O 3 post-treatment technique to the TiO 2 -adsorbed dye allows the dye to remain in electronic contact with both the semiconductor surface and a surrounding electrolyte solution, the combination of which makes this technique promising for numerous other electrochemical photovoltaic and photocatalytic applications, especially those involving the dye-sensitized evolution of oxygen.

  14. Evidence for halogen bond covalency in acyclic and interlocked halogen-bonding receptor anion recognition

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Robinson, Sean W.; Mustoe, Chantal L.; White, Nicholas G.

    The synthesis and anion binding properties of novel halogen-bonding (XB) bis-iodotriazole-pyridinium-containing acyclic and [2]catenane anion host systems are described. The XB acyclic receptor displays selectivity for acetate over halides with enhanced anion recognition properties compared to the analogous hydrogen-bonding (HB) acyclic receptor. A reversal in halide selectivity is observed in the XB [2]catenane, in comparison to the acyclic XB receptor, due to the interlocked host’s unique three-dimensional binding cavity, and no binding is observed for oxoanions. Notable halide anion association constant values determined for the [2]catenane in competitive organic–aqueous solvent mixtures demonstrate considerable enhancement of anion recognition as compared tomore » the HB catenane analogue. X-ray crystallographic analysis of a series of halide catenane complexes reveal strong XB interactions in the solid state. These interactions were studied using Cl and Br K-edge X-ray Absorption Spectroscopy (XAS) indicating intense pre-edge features characteristic of charge transfer from the halide to its bonding partner (σ AX←X–* ← X1s), and providing a direct measure of the degree of covalency in the halogen bond(s). Lastly, the data reveal that the degree of covalency is similar to that which is observed in transition metal coordinate covalent bonds. These results are supported by DFT results, which correlate well with the experimental data.« less

  15. Evidence for halogen bond covalency in acyclic and interlocked halogen-bonding receptor anion recognition

    DOE PAGES

    Robinson, Sean W.; Mustoe, Chantal L.; White, Nicholas G.; ...

    2014-12-05

    The synthesis and anion binding properties of novel halogen-bonding (XB) bis-iodotriazole-pyridinium-containing acyclic and [2]catenane anion host systems are described. The XB acyclic receptor displays selectivity for acetate over halides with enhanced anion recognition properties compared to the analogous hydrogen-bonding (HB) acyclic receptor. A reversal in halide selectivity is observed in the XB [2]catenane, in comparison to the acyclic XB receptor, due to the interlocked host’s unique three-dimensional binding cavity, and no binding is observed for oxoanions. Notable halide anion association constant values determined for the [2]catenane in competitive organic–aqueous solvent mixtures demonstrate considerable enhancement of anion recognition as compared tomore » the HB catenane analogue. X-ray crystallographic analysis of a series of halide catenane complexes reveal strong XB interactions in the solid state. These interactions were studied using Cl and Br K-edge X-ray Absorption Spectroscopy (XAS) indicating intense pre-edge features characteristic of charge transfer from the halide to its bonding partner (σ AX←X–* ← X1s), and providing a direct measure of the degree of covalency in the halogen bond(s). Lastly, the data reveal that the degree of covalency is similar to that which is observed in transition metal coordinate covalent bonds. These results are supported by DFT results, which correlate well with the experimental data.« less

  16. (5-n-Butyl-10,20-diiso­butyl­porphyrin­ato)nickel(II)

    PubMed Central

    Senge, Mathias O.; Dahms, Katja

    2014-01-01

    The asymmetric unit of the title compound, [Ni(C32H36N4)], contains two independent mol­ecules exhibiting an overall ruffled conformation of the porphyrin macrocycle and differing mainly in the positions of the methyl groups. The average Ni—N bond lengths are 1.912 (2) and 1.910 (2) Å in the two mol­ecules. The mol­ecules form a closely spaced lattice structure in which neighbouring porphyrins are oriented in a nearly perpendicular fashion to each other. The compound was prepared via nucleophilic substitution of (5,15-diiso­butyl­porphyrinato)nickel(II) with n-butyl­lithium. PMID:25161518

  17. 40 CFR 721.8875 - Substituted halogenated pyridinol.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8875 Substituted halogenated pyridinol. (a) Chemical substances and significant new uses... pyridinol (PMN P-88-1273) is subject to reporting under this section for the significant new uses described...

  18. 40 CFR 721.8750 - Halogenated substituted pyridine.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8750 Halogenated substituted pyridine. (a) Chemical substances and significant new uses... pyridine (PMN P-86-838) is subject to reporting under this section for the significant new uses described...

  19. 40 CFR 721.8875 - Substituted halogenated pyridinol.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8875 Substituted halogenated pyridinol. (a) Chemical substances and significant new uses... pyridinol (PMN P-88-1273) is subject to reporting under this section for the significant new uses described...

  20. 40 CFR 721.8850 - Disubstituted halogenated pyridinol.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8850 Disubstituted halogenated pyridinol. (a) Chemical substances and significant new uses... pyridinol (PMN P-88-1274) is subject to reporting under this section for the significant new uses described...