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Porphyrin
Kinds of Porphyrin Terms modified by Porphyrin Selected AbstractsRedox Active Two-Component Films of Palladium and Covalently Linked Zinc Porphyrin,Fullerene DyadELECTROANALYSIS, Issue 9 2006Marta Plonska Abstract Redox active films have been generated electrochemically by the reduction of dyads consisting of fullerene C60 covalently linked to zinc meso -tetraphenyloporphyrin, ZnPC60, and palladium acetate. The films are believed to consist of a polymeric network formed via covalent bonds between the palladium atoms and the fullerene moieties. In these films, the zinc porphyrin moiety is covalently linked to the polymeric chains through the pyrrolidine ring of the fullerene. The ZnPC60/Pt films are electrochemically active in both positive and negative potential excursions. At positive potentials, two oxidation steps for the zinc porphyrin are observed. In the negative potential range, electron transfer processes involving the zinc porphyrin and the fullerene entities are observed. Film formation is also accompanied by palladium deposition on the electrode surface. The presence of a metallic phase in the film influences its morphology, structure and electrochemical properties. [source] Highly Efficient Visible-Light-Induced Photocleavage of DNA by a Ruthenium-Substituted Fluorinated PorphyrinEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2009Michelle Cunningham Abstract A new porphyrin, meso -5-(pentafluorophenyl)-10,15,20-tris(4-pyridyl)porphyrin, has been synthesized. Coordination of two [Ru(bipy)2Cl]+ moieties (where bipy = 2,2,-bipyridine) to the pyridyl nitrogen atoms in the 10,15-positions gives the target complex. Electronic transitions associated with the ruthenium,porphyrin include an intense Soret band and four less intense Q-bands in the visible region of the spectrum. An intense ,,,* transition in the UV region associated with the bipyridyl groups and a metal-to-ligand charge-transfer (MLCT) band appearing as a shoulder to the Soret band are also observed. Electrochemical properties associated with the complex include a redox couple in the cathodic region with E1/2 = ,0.84 V vs. Ag/AgCl attributed to the porphyrin and a redox couple in the anodic region at E1/2 = 0.79 V vs. Ag/AgCl due to the RuIII/II couple. DNA titrations and ethidium bromide displacement experiments indicate the ruthenium porphyrin interacts with DNA potentially through a partial intercalation mechanism. Irradiation of aqueous solutions of the ruthenated complex and supercoiled DNA at a 100:1 base pair/complex ratio with visible light above 400 nm indicates that the complex causes double-strand breaks of the DNA.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Synthesis and Physicochemical Characterization of Bis(macrocycles) Involving a Porphyrin and a meso -Substituted Corrole , X-ray Crystal Structure of a [(Free-base porphyrin),corrole]bis(pyridine)cobalt ComplexEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2005Jean-Michel Barbe Abstract A very efficient, simple synthesis of face-to-face porphyrin,corrole free-bases bearing substituents at the meso positions of the corrole ring is reported. Starting from the (porphyrin,aldehyde)zinc species 1Zn, porphyrin,corrole free-bases (3M, 3C) are obtained in two steps, in fairly good yields (40,43,%), compared to 11 steps for their corrole ,-pyrrole-substituted counterparts. Moreover, the possibility to directly synthesize the free-base (porphyrin,corrole)cobalt complex (5M or 5C) allows for the further preparation of heterodimetallic derivatives. Crystals of the bis(pyridine) adduct of 5M have been grown; the molecular structure clearly shows that the two pyridine molecules are coordinated to the cobalt ion in endo and exo positions, leading to an open-mouth geometry of the bis(macrocycle). The structure of 5M(py)2also shows intermolecular ,,, interactions along the [1,0,0] direction, leading to stacking of the complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Synthesis of Triazole-Bridged Unsymmetrical Porphyrin Dyads and Porphyrin,Ferrocene ConjugatesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2010Vijayendra S. Shetti Abstract A simple method has been used to synthesize four porphyrin azides with cores such as N4, N3S, N2SO and N2S2 in 60,90,% yields by treating the corresponding aminoporphyrins with tert -butyl nitrite (tBuONO) and azidotrimethylsilane (TMSN3) in THF/CH3CN under mild reaction conditions. The hitherto unknown aminoporphyrins with heteroatom cores were synthesized from their corresponding nitroporphyrins by standard SnCl2/HCl reduction. The azidoporphyrins were used to synthesize six triazole-bridged unsymmetrical porphyrin dyads containing two different types of porphyrin sub-units as well as five triazole-bridged porphyrin,ferrocene conjugates under CuI -catalyzed "click" reaction conditions. Various CuI -catalyzed reaction conditions were studied and the best yields of triazole-bridged dyads and conjugates were obtained with CuI/DIPEA in THF/CH3CN at room temperature for overnight. The unsymmetrical porphyrin dyads and porphyrin,ferrocene conjugates were characterized by various spectroscopic and electrochemical techniques. In unsymmetrical porphyrin dyads, the NMR, absorption and electrochemical studies indicate a weak interaction between the two porphyrin sub-units. However, preliminary photophysical studies support an efficient singlet-singlet energy transfer from one porphyrin unit to another in five unsymmetrical dyads reported here. In porphyrin,ferrocene conjugates, the fluorescence of porphyrin was quenched significantly due to photo-induced electron transfer from ferrocene to porphyrin. [source] Kinetics of (Porphyrin)manganese(III)-Catalyzed Olefin Epoxidation with a Soluble Iodosylbenzene DerivativeEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 12 2006James P. Collman Abstract We examined the kinetics of a well-behaved system for homogeneous porphyrin-catalyzed olefin epoxidation with a soluble iodosylbenzene derivative 1 as the terminal oxidant and Mn(TPFPP)Cl (2) as the catalyst. The epoxidation rates were measured by using the initial rate method, and the epoxidation products were determined by gas chromatography. The epoxidation rate was found to be first order with respect to the porphyrin catalyst and zero order on the terminal oxidant. In addition, we found the rate law to be sensitive to the nature and concentration of olefin substrates. Saturation kinetics were observed with all olefin substrates at high olefin concentrations, and the kinetic data are consistent with a Michaelis,Menten kinetic model. According to the observed saturation kinetic results, we propose that there is a complexation between the active oxidant and the substrate, and the rate-determining step is thought to be the breakdown of this putative substrate,oxidant complex that generates the epoxidation products and the resting state porphyrin catalyst. Competitive epoxidations further indicate a reversible complexation of the active oxidant and the olefin substrate. The activation parameters ,H, and ,S, for the oxygen-transfer process (k2) in the cis -cyclooctene epoxidation were determined to be 12.3,±,0.9 kcal,mol,1 and,15.6,±,3.2 cal,mol,1,K,1, respectively. In addition, the Hammett constant ,+ was measured for the epoxidation of para -substituted styrenes, and the value of ,0.27,±,0.04 is too low to be consistent with the involvement of a discrete carbocation in the transition state. We also prepared a (porphyrin)manganese catalyst immobilized on silica support, and found the epoxidation of cis -cyclooctene catalyzed by this heterogeneous catalyst proceeds at virtually the same turnover frequency as by the homogeneous porphyrin catalyst. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] A Graphene Hybrid Material Covalently Functionalized with Porphyrin: Synthesis and Optical Limiting PropertyADVANCED MATERIALS, Issue 12 2009Yanfei Xu An organic solution-processable functionalized graphene (SPFGraphene) hybrid material with porphyrins is reported for the first time. FTIR, UV-vis absorption, and TEM studies confirm the covalent functionalization of the graphene. A superior optical limiting effect, better than the benchmark optical limiting material C60 and the control sample, is observed. [source] Ordered Supramolecular Assembly of Porphyrin,Fullerene Composites on Nanostructured SnO2 Electrodes,ADVANCED MATERIALS, Issue 19 2006S. Kang Very high photocurrent generation is seen for an ordered supramolecular composite structure of C60 and porphyrin assembled on SnO2 electrodes. The simple substitution of methoxy groups at the meta positions of the meso -phenyl groups on the porphyrin ring leads to the ordered stacking arrangement shown in the figure, with separate electron and hole transport paths along the 1D porphyrin chains and 2D C60 sheets. [source] An Efficient Synthesis of Poly(ethylene glycol)-Supported Iron(II) Porphyrin using a Click Reaction and its Application for the Catalytic Olefination of AldehydesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Suman Abstract The first successful synthesis of poly(ethylene glycol) (PEG) immobilized iron(II) porphyrin using a copper-catalyzed azide-alkyne [3+2],cycloaddition is reported. In contrast to the existing methods for the synthesis of PEG-immobilized metalloporphyrins, the click method offers better catalyst loading under comparatively mild reaction conditions. The prepared complex 5 (PEG-C51H39FeN7O) was found to be an efficient catalyst for the selective olefination of aldehydes with ethyl diazoacetate in the presence of triphenylphosphine and afforded excellent olefin yields with high (E) selectivities. The PEG-supported catalyst 5 was readily recovered by precipitation and filtration and was recycled for up to ten runs without significant loss of activity. [source] Porphyrin-based, light-activated antimicrobial materialsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2003Jadranka Bozja Abstract New light-activated antimicrobial materials with a potentially wide range of possible uses in civilian settings were synthesized by the grafting of protoporphyrin IX and zinc protoporphyrin IX to nylon fibers. These fibers were shown to be active against Staphylococcus aureus at light exposures of 10,000 lux and greater and against Escherichia coli at 60,000 lux. They were ineffective against both strains in the absence of light. At 40,000 lux, these fibers showed increased antimicrobial activity against S. aureus with increasing exposure time. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2297,2303, 2003 [source] Synthesis, Photophysical Studies and Anticancer Activity of a New Halogenated Water-Soluble PorphyrinPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2007Janusz M. D, browski ABSTRACT A water-soluble halogenated porphyrin, namely 5,10,15,20 -tetrakis(2-chloro-3-sulfophenyl)porphyrin (TCPPSO3H), was prepared and evaluated as sensitizer for photodynamic therapy (PDT). Photophysical properties of TCPPSO3H, such as high photostability, long triplet lifetime and high singlet oxygen quantum yield suggest high effectiveness of this class of halogenated porphyrins in PDT. TCPPSO3H is non-toxic in the dark and causes a significant photodynamic effect examined against MCF7 (human breast carcinoma), SKMEL 188 (human melanoma) and S91(mouse melanoma) cell lines upon red light irradiation (cutoff < 600 nm) at low light doses. Time-dependent cellular uptake of TCPPSO3H reached plateau at 120 min and was the highest for S91, 20% lower for MCF7 and 70% lower for SKMEL 188. Our results show that this halogenated water-soluble porphyrin is an efficient photosensitizer and reveal the potential of this class of compounds as PDT agents. [source] Fused Pyrene,Diporphyrins: Shifting Near-Infrared Absorption to 1.5,,m and Beyond,ANGEWANDTE CHEMIE, Issue 32 2010Vyacheslav Die direkte Anellierung von Pyrensystemen an Diporphyrine liefert Pyren-Diporphyrin-Hybridverbindungen (C(Pyren),rot, C(Porphyrin),dunkelblau, N,hellblau, Zn,grün) mit einer Nahinfrarot(NIR)-Absorption bei Wellenlängen, die für die Telekommunikation wichtig sind. Außerdem erreichen sie eine der höchsten externen Quantenausbeuten unter den organischen Farbstoffen. [source] Porphyrin "Lego Block" Strategy To Construct Directly meso,, Doubly Linked Porphyrin Rings,ANGEWANDTE CHEMIE, Issue 21 2010Jianxin Song Dr. Eingerastet: Die Suzuki-Miyaura-Kupplung von ,,,,-diborylierten mit meso,meso,-dibromierten Porphyrinblöcken wird für den Aufbau direkt doppelt meso-,-verknüpfter Porphyrinringe genutzt, darunter zweier Tetraporphyrinringe, Hexaporphyrinringe und eines verbrückten Heptaporphyrins (siehe Bild). [source] Use of Short Duplexes for the Analysis of the Sequence-Dependent Cleavage of DNA by a Chemical Nuclease, a Manganese PorphyrinCHEMBIOCHEM, Issue 12 2005Sophie Mourgues Abstract A manganese porphyrin, manganese(III)-bis(aqua)- meso -tetrakis(4- N -methylpyridiniumyl)porphyrin, in the presence of KHSO5 is able to perform deoxyribose or guanine oxidation depending on its mode of interaction with DNA. These two reactions involve an oxygen-atom transfer or an electron transfer, respectively. The oxidative reactivity of the manganese-oxo porphyrin was compared on short oligonucleotide duplexes of different sequences. The major mechanism of DNA damage is due to deoxyribose hydroxylation at a site of strong interaction, an (A,T)3 sequence. Guanine oxidation by electron transfer was found not to be competitive with this major mechanism. It was found that a single intrastrand guanine was three orders of magnitude less reactive than an (A,T)3 sequence. The reactivity of a 5,-GG sequence was found to be intermediate and was estimated to be two orders of magnitude less than that of an (A,T)3 site. Short oligonucleotide duplexes, as double-stranded-DNA models, proved to be convenient tools for the study of the comparative reactivity of this reagent toward different sequences of DNA. However, they showed a particular reactivity at their terminal base pairs (the "end effect") that biased their modeling capacity for double-helix-DNA models. [source] Synthesis and Spectroscopic Properties of a Covalently Linked Porphyrin,Fullerene C60 Dyad.CHEMINFORM, Issue 41 2006M. Elisa Milanesio Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Epoxidation of Olefins Catalyzed by Manganese(III) Porphyrin in a Room Temperature Ionic Liquid.CHEMINFORM, Issue 22 2003Zhen Li Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Probing the Donor,Acceptor Proximity on the Physicochemical Properties of Porphyrin,Fullerene Dyads: "Tail-On" and "Tail-Off" Binding Approach.CHEMINFORM, Issue 38 2001Francis D'Souza Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Efficient and Selective Epoxidation of Alkenes by Supported Manganese Porphyrin under Ultrasonic Irradiation.CHEMINFORM, Issue 15 2001Valiollah Mirkhani Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Regioselective Oxidations of Equilenin Derivatives Catalyzed by a Rhodium(III) Porphyrin Complex , Contrast with the Manganese(III) Porphyrin.CHEMINFORM, Issue 3 2001Jerry Yang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: A New General Method for Selective ,-Polynitration of Porphyrins; Preparation and Redox Properties of Zn-Porphyrins Bearing One Through to Eight ,-Nitro Substituents and X-Ray Structure of the First Zn ,-Pernitro Porphyrin.CHEMINFORM, Issue 2 2001Magali Palacio Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Photooxidation of N-Confused Porphyrin: A Route to N-Confused Biliverdin AnaloguesCHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2010Jacek Wojaczy, ski Dr. Clarity through confusion: The photooxidation of an N-confused porphyrin dianion provides a unique N-confused biliverdin analogue with two types of coordination surroundings: (NNNO) and (CNOO), as demonstrated by a palladium(II) complex (see figure). [source] DABCO-Mediated Self-Assembly of Zinc Porphyrin,Perylene Bisimide Monodisperse Multichromophoric Nanoparticles,CHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2010Peter Osswald Dr. Line up! Fourfold zinc porphyrin functionalized perylene bisimide has afforded well-defined supramolecular particles by intramolecular cofacial bridging of zinc porphyrin units through the ditopic ligand DABCO as revealed by UV/Vis and NMR spectroscopy and AFM studies (see figure). [source] Dendritic Porphyrin,Fullerene Conjugates: Efficient Light-Harvesting and Charge-Transfer EventsCHEMISTRY - A EUROPEAN JOURNAL, Issue 45 2009Sebastian Schlundt Abstract A novel dendritic C60 -H2P-(ZnP)3 (P=porphyrin) conjugate gives rise to the successful mimicry of the primary events in photosynthesis, that is, light harvesting, unidirectional energy transfer, charge transfer, and charge-shift reactions. Owing, however, to the flexibility of the linkers that connect the C60, H2P, and ZnP units, the outcome depends strongly on the rigidity/viscosity of the environment. In an agar matrix or Triton X-100, time-resolved transient absorption spectroscopic analysis and fluorescence-lifetime measurements confirm the following sequence. Initially, light harvesting is seen by the peripheral C60 -H2P- *(ZnP)3 conjugate. Once photoexcited, a unidirectional energy transfer funnels the singlet excited-state energy to H2P to form C60 -*(H2P)-(ZnP)3, which powers an intramolecular charge transfer that oxidizes the photoexcited H2P and reduces the adjacent C60 species. In the correspondingly formed (C60)., -(H2P).+ -(ZnP)3 conjugate, an intramolecular charge-shift reaction generates (C60)., -H2P-(ZnP)3.+, in which the radical cation resides on one of the three ZnP moieties, and for which lifetimes of up to 460,ns are found. On the other hand, investigations in organic media (i.e., toluene, THF, and benzonitrile) reveal a short cut, that is, the peripheral ZnP unit reacts directly with C60 to form (C60)., -H2P-(ZnP)3.+. Substantial configurational rearrangements, placing ZnP and C60 in proximity to each other,are, however, necessary to ensure the required through space interactions (i.e., close approach). Consequently, the lifetime of (C60)., -H2P-(ZnP)3.+ is as short as 100,ps in benzonitrile. [source] Role of Environmental Factors on the Structure and Spectroscopic Response of 5,-DNA,Porphyrin Conjugates Caused by Changes in the Porphyrin,Porphyrin InteractionsCHEMISTRY - A EUROPEAN JOURNAL, Issue 44 2009Angela Mammana Dr. Abstract We have explored the utility, strength, and limitation of through-space exciton-coupled circular dichroism in determination of the secondary structure of optically active chromophoric nanoarrays using the example of end-capped porphyrin, and metalloporphyrin,oligodeoxynucleotide conjugates. We put special emphasis on the explanation of the origin and significance of the distinctive multiple bands in the CD spectra (trisignate and tetrasignate CD bands). Such CD profiles are often observed in chiral aggregates or multichromophoric arrays but have never before been studied in detail. We found that variation of temperature and ionic strength has a profound effect on the geometry of the porphyrin,DNA conjugates and thus the nature of electronic interactions. At lower temperatures and in the absence of NaCl all three 5,-DNA,porphyrin conjugates display negative bisignate CD exciton couplets of variable intensity in the Soret region resulting from through-space interaction between the electric transition dipole moments of the two end-capped porphyrins. As the temperature is raised these exciton couplets are transformed into single positive bands originating from the porphyrin,single-strand DNA interactions. At higher ionic strengths and low temperatures, multisignate CD bands are observed in the porphyrin Soret region. These CD signature bands originate from a combination of intermolecular, end-to-end porphyrin,porphyrin stacking between duplexes and porphyrin,DNA interactions. The intermolecular aggregation was confirmed by fluorescence and absorption spectroscopy and resonance light scattering. DeVoe theoretical CD calculations, in conjunction with molecular dynamics simulations and Monte Carlo conformational searches, were used to mimic the observed bisignate exciton-coupled CD spectra as well as multiple CD bands. Calculations correctly predicted the sign and shape of the experimentally observed CD spectra. These studies reveal that the exciton-coupled circular dichroism is a very useful technique for the determination of the structure of optically active arrays. [source] Single-Step Electron Transfer on the Nanometer Scale: Ultra-Fast Charge Shift in Strongly Coupled Zinc Porphyrin,Gold Porphyrin DyadsCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2008Jérôme Fortage Dr. Abstract The synthesis, electrochemical properties, and photoinduced electron transfer processes of a series of three novel zinc(II),gold(III) bisporphyrin dyads (ZnPSAuP+) 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,Å. 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 .+ZnPSAuP., 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 (,=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 ZnPAuP+ dyads linked via meso -phenyl groups to oligo-phenyleneethynylene spacers. This study demonstrates the critical impact of the attachment position of the spacer on the porphyrin on the electron transfer rate, and this strategy can represent a useful approach to develop molecular photonic devices for long-range charge separations. [source] Diboryl and Diboranyl Porphyrin Complexes: Synthesis, Structural Motifs, and Redox Chemistry: Diborenyl Porphyrin or Diboranyl Isophlorin?CHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2007Andre Weiss Dr. Abstract The syntheses of diboryl porphyrin complexes [(BX2)2(ttp)] (ttp: dianion of tetra- p -tolylporphyrin) and the BB single-bond diboranyl complexes [(BX)2(ttp)] (X=F, Cl, Br, I) are given. The former are prepared from the reactions of BX3 (X=F, Cl) with [Li2(ttp)] and the latter from B2Cl4 (X=Cl), the reaction of SbF3 with [(BCl)2(ttp)] (for X=F), and, in the cases of X=Br or I, in a remarkable reductive coupling reaction resulting directly from the reaction of BBr3 or BI3 with [Li2(ttp)]. Density functional theory (DFT) calculations on the thermochemical parameters for the reductive coupling reactions (and those calculated for related dipyrromethene complexes) indicate that a combination of the reducing ability of bromide and iodide ions combined with the constrained environment of the porphyrin ligand contribute to the driving force. The reductive coupling is also observed in the reaction of [(BCl2)2(ttp)] with nBuLi to give [(BnBu)2(ttp)], which was characterised crystallographically. The reaction of [(BCl)2(ttp)] with catechol gives a boron catecholato porphyrin complex, [B2(O2C6H4)(ttp)]. Chloride abstraction from [(BCl)2(ttp)] gives the planar dication [B2(ttp)]2+, whereas chemical reduction of [(BCl)2(ttp)] by using magnesium anthracenide gives a neutral complex, [B2(ttp)], in which the TTP ligand has been reduced by two electrons to give an unusual example of an isophlorin complex. The cationic and neutral complexes [B2(ttp)]2+ and [B2(ttp)] were characterised through a combination of spectroscopic data that is supported by DFT calculations on the porphine analogues. [source] Precursors of Biological Cofactors from Ultraviolet Irradiation of Circumstellar/Interstellar Ice AnaloguesCHEMISTRY - A EUROPEAN JOURNAL, Issue 17 2005Uwe J. Meierhenrich Priv.-Doz. Abstract Biological cofactors include functionalized derivatives of cyclic tetrapyrrole structures that incorporate different metal ions. They build up structural partnerships with proteins, which play a crucial role in biochemical reactions. Porphyrin, chlorin, bacteriochlorin, and corrin are the basic structures of cofactors (heme, chlorophyll, bacteriochlorophyll, siroheme, F 430, and vitamin B12). Laboratory and theoretical work suggest that the molecular building blocks of proteins (,-amino acids) and nucleic acids (carbohydrates, purines, and pyrimidines) were generated under prebiotic conditions. On the other hand, experimental data on the prebiotic chemistry of cofactors are rare. We propose to search directly for the pathways of the formation of cofactors in the laboratory. Herein we report on the detection of N-heterocycles and amines in the room-temperature residue obtained after photo- and thermal processing of an interstellar ice analogue under high vacuum at 12 K. Among them, hexahydro-1,3,5-triazine and its derivatives, together with monopyrrolic molecules, are precursors of porphinoid cofactors. Hexahydropyrimidine was also detected. This is the first detection of these compounds in experiments simulating circumstellar/interstellar conditions. Except for 2-aminopyrrole and 2,4-diaminofuran, which were only found in 13C-labeled experiments, all the reported species were detected in both 12C- and 13C-labeled experiments, excluding contamination. The molecules reported here might be present in circumstellar/interstellar grains and cometary dust and could be detected by the Stardust and Rosetta missions. [source] Two-Dimensional Self-Assembly of a Porphyrin,Polypyridyl Ruthenium(II) Hybrid on HOPG Surface through Metal,Ligand InteractionsCHEMPHYSCHEM, Issue 9 2010Aimei Gao Dr. Abstract The synthesis and self-assembly behavior of porphyrin,polypyridyl ruthenium(II) hybrid, which consists of a flexible alkyl chain attached with two conjugated moieties is described. The electronic absorption spectrum and emission spectra show that the [C8 -TPP-(ip)Ru(phen)2](ClO4)2, abbreviated as (C8ip)TPPC has optical properties. Scanning tunneling microscopy (STM) studies found that the ,,, interaction and metal,ligand interaction allow (C8ip)TPPC to form self-assembled structure and have an edge-on orientation on the highly oriented pyrolytic graphite (HOPG) surface. The multidentate structure in (C8ip)TPPC molecules act as linkers between the molecules and form metal,ligand coordination, which forces the assembly process in the direction of stable columnar arrays. In addition, although the sample was stored for two months in ambient conditions, STM experiments showed that the order of (C8ip)TPPC self-assembly only slightly decreased which indicates that the self-assembled monolayer is stable. This work demonstrates that introducing a metal-ligand in the porphyrin-polypyridyl compound is a useful strategy to obtain novel surface assemblies. [source] Tunable Soret-Band Splitting of an Amphiphilic Porphyrin by Surface PressureCHEMPHYSCHEM, Issue 11 2008Gustavo de Miguel Dr. Tuning with pressure: Splitting of the Soret band in the novel amphiphilic porphyrin (OD)3TPPS3 is reversibly tuned by applying surface pressure (see figure). The degenerated transition of the Soret band is broken as a result of the formation of an ordered monolayer, which causes individual coupling of the components Bx and By of the Soret band. [source] Nonlinear Optical Properties of Ferrocene- and Porphyrin,[60]Fullerene DyadsCHEMPHYSCHEM, Issue 7 2007Evangelia Xenogiannopoulou Dr. Abstract A series of novel [60]fullerene,ferrocene and [60]fullerene,porphyrin dyads, in which a fullerene and an electron donating moiety are attached through a flexible triethylene glycol linker are synthesized and their nonlinear optical (NLO) response studied. Specifically, the third-order susceptibility ,(3) of all fullerene derivatives are measured in toluene solutions by the optical Kerr effect (OKE) technique using 532 nm, 35 ps laser pulses and their second hyperpolarizability , are determined. All fullerene dyads studied exhibit enhancement of their NLO response compared to pristine fullerenes which has been attributed to the formation of a charge separated state. All experimentally measured hyperpolarizability , values are also calculated by the semiempirical methods AM1 and PM3. A good correlation is found between the theoretical and experimental values, suggesting that simple semiempirical methods can be employed for the designing and optimization of the fullerene-containing dyads displaying improved nonlinear responses. [source] Electrochemical Reduction of S(IV) Compounds in Water-Ethanol Solutions at Nafion/Tetraruthenated Porphyrins Glassy Carbon Modified ElectrodesELECTROANALYSIS, Issue 3 2010Karla Calfumán Abstract This work describes electrocatalytic detection of S(IV) compounds in water-ethanol solutions under acidic conditions, on a glassy carbon electrode modified with Co(II) tetraruthenated porphyrin electrostatically assembled onto a Nafion film. The Ipc current shows a linear relationship with the concentration of S(IV) oxo-anions. Controlled potential electrolysis shows that thiosulfate was detected as reaction product. Rotating disk electrode and UV-visible spectroelectrochemistry experiments showed a kinetic limitation to the electron transfer controlled by charge propagation in the film and the formation of an intermediary between Co center and S(IV) species. The reproducibility of the modification methodology presents a RSD of 4.1%. [source] | |||||||||||||||||||||||||||||||||||||||||||