- Electrochemical analysis of iron-porphyrin-catalyzed CO2 reduction under photoirradiation
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In this study, the photochemical reaction of a metal-complex-based catalyst was analyzed by electrochemical measurements. A well-known catalyst for the CO2 reduction reaction, meso-tetraphenylporphyrin iron(III) chloride (Fe(tpp)Cl), was selected as the target analyte. Although the analysis of the electrochemical response of Fe(tpp)Cl under photoirradiation with conventional cyclic voltammetry (CV) was not allowed, the adaptation of thin layer cyclic voltammetry (TLCV) enabled us to detect the photochemical reaction of Fe(tpp)Cl. The influence of photoirradiation on the electrochemical property of Fe(tpp)Cl was investigated both under Ar and CO2 atmospheres. Although the thin layer cyclic voltammograms of Fe(tpp)Cl upon photoirradiation under an Ar atmosphere were almost the same as those measured in the dark, the measurements under a CO2 atmosphere clearly indicated the change of the electrochemical response upon photoirradiation. The detailed analysis of this phenomenon revealed that the photoinduced decarbonylation reaction regenerates the original [FeII(tpp)] complex under photoirradiation.
- Fukatsu, Arisa,Kondo, Mio,Okabe, Yuki,Masaoka, Shigeyuki
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- Synthesis, electrochemical and spectroelectrochemical characterization of iron(III) tetraarylporphyrins containing four β, β ′-butano and β, β ′-benzo fused rings
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Six iron(III) tetraarylporphyrins containing four b,b?-butano or b,b?-benzo fused rings were synthesized and characterized by electrochemistry and spectroelectrochemistry in nonaqueous media. The examined compounds are represented as butano(TpYPP)FeCl and
- Xu, Weijie,Fang, Yuanyuan,Ou, Zhongping,Chen, Mingyuan,Kadish, Karl M.
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- Immobilization of Fe, Mn and Co tetraphenylporphyrin complexes in MCM-41 and their catalytic activity in cyclohexene oxidation reaction by hydrogen peroxide
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Metalloporphyrin catalysts are able to carry out selective oxidation of organic substrates with several oxidizing agents. Recently, mesoporous materials have been studied as supports because they present high specific surface area, better dispersion and regeneration properties. This work presents the results of synthesis, characterization and application of three metalloporphyrin catalysts (FeTPPCl, MnTPPCl and CoTPP, where TPP = tetraphenylporphyrin) anchored on MCM-41, in the reaction of cyclohexene oxidation with hydrogen peroxide. A modified sol-gel preparation was chosen for the synthesis of the MCM-41 mesoporous material, as well as the anchoring was followed by Soxhlet extraction to ensure strong adsorption of the complex. The supported materials were much more stable than pure metalloporphyrins. The synthesized catalysts were characterized by UV-vis, FTIR, XRD, ICP-AES, 29Si MAS-NMR and thermal analysis, before and after incorporation. Evidence of the metalloporphyrin immobilization was confirmed by elemental analysis and their activity in the oxidation reaction. FeTPPCl/MCM-41 showed higher conversion than CoTPP/MCM-41 and MnTPPCl/MCM-41. However, MnTPPCl/MCM-41 even in low concentration on the support showed a good conversion for the direct oxidation of cyclohexene with the highest turnover number (1.54 × 105). All catalysts showed similar selectivity that favors allylic oxidation products over epoxidation. No leaching of the metalloporphyrins was observed after the reaction.
- Costa, Andréia A.,Ghesti, Grace F.,de Macedo, Julio L.,Braga, Valdeilson S.,Santos, Marcello M.,Dias, José A.,Dias, Sílvia C.L.
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- The Formation of Heterobinuclear μ-Oxo Cr-O-Fe Porphyrin Complexes by the Reaction of Oxochromium(IV) and Iron(II) Porphyrins
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The reaction of α,β,γ,δ-tetraphenylporphinato-oxochromium(IV) with α,β,γ,δ-tetraphenylporphinato-iron(II)bis(piperidine) in toluene results in the formation of the mixed-metal complex (TPP)CrIII-O-FeIII(TPP) characterised
- Liston, David J.,Murray, Keith S.,West, Bruce O.
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- Hydrogen bonding in metalloporphyrin reactions. Reaction of (tetraphenylporphinato)iron(III) chloride and N-methylimidazole
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The reaction of N-methylimidazole, N-MeIm, and high-spin five-coordinate (tetraphenylporphinato)iron(III) chloride, Fe(TPP)Cl, proceeds rapidly to form low-spin Fe(TPP)(N-MeIm)2+Cl-. During the reaction an intermediate mono(imidazole) complex, Fe(TPP)(N-MeIm)Cl, can be detected as a transient at room temperature and can be trapped for longer periods at low temperatures. The optical spectrum, ESR spectrum, and formation constant of the intermediate show it to be a high-spin six-coordinate species, proving that a spin change occurs upon addition of the second N-MeIm to form Fe-(TPP)(N-MeIm)2+Cl-. Kinetic studies in several solvents show that the rate-determining step in the reaction of N-MeIm and Fe(TPP)Cl is chloride ionization from the mono(imidazole) intermediate. The chloride ionization rate constant, k1, is strongly dependent on the ability of the solvent to hydrogen bond to the departing chloride in the transition state as shown by a very good correlation of k1 with Gutmann acceptor numbers for six solvents. Correlations do not exist with other common solvent parameters such as dielectric constant. Low concentrations of potential hydrogen bonders like trifluoroethanol and phenol have a large accelerating effect on k1. The relationship between this work and possible hydrogen bonding involving distal and proximal histidines in hemoprotein-mediated reactions is discussed.
- Doeff, Marca M.,Sweigart
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- Dioxygen Activation in the Photochemistry of some Oxo-metalloporphyrin Complexes
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Ultraviolet irradiation of the peroxo-complexes and (tpp = 5,10,15,20-tetraphenylporphyrinate) induces elimination of O2 and generation of the corresponding oxometalloporphyrins and .Reductive elimination o
- Bergamini, Paola,Sostero, Silvana,Traverso, Orazio,Deplano, Paola,Wilson, Lon J.
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- Construction of secondary coordination sphere boosts electrochemical CO 2 reduction of iron porphyrins
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Iron porphyrins with simple aminophenyl substitution are synthesized and their electrochemical CO2 reduction properties are studied. Fe-1, bearing an amino group in the ortho position of the phenyl ring exhibits an improved catalytic turn over frequency (
- Liu, Guiyu,Fan, Ying-Jie,Zhang, Jun-Long
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- Syntheses and CO2 reduction activities of π-expanded/extended iron porphyrin complexes
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The construction of molecular catalysts that are active toward CO2 reduction is of great significance for designing sustainable energy conversion systems. In this study, we aimed to develop catalysts for CO2 reduction by introducing
- Okabe, Yuki,Lee, Sze Koon,Kondo, Mio,Masaoka, Shigeyuki
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- Quick and Easy Method to Dramatically Improve the Electrochemical CO2 Reduction Activity of an Iron Porphyrin Complex
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The development of artificial molecular catalysts for CO2 reduction is the key to solving energy and environmental problems. Although chemical modifications can generally improve the catalytic activity of this class of compounds, they often req
- Kondo, Mio,Kosugi, Kento,Masaoka, Shigeyuki
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- Mechanism of Catalytic O2 Reduction by Iron Tetraphenylporphyrin
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The catalytic reduction of O2 to H2O is important for energy transduction in both synthetic and natural systems. Herein, we report a kinetic and thermochemical study of the oxygen reduction reaction (ORR) catalyzed by iron tetraphenylporphyrin (Fe(TPP)) in N,N′-dimethylformamide using decamethylferrocene as a soluble reductant and para-toluenesulfonic acid (pTsOH) as the proton source. This work identifies and characterizes catalytic intermediates and their thermochemistry, providing a detailed mechanistic understanding of the system. Specifically, reduction of the ferric porphyrin, [FeIII(TPP)]+ , forms the ferrous porphyrin, FeII(TPP), which binds O2 reversibly to form the ferricsuperoxide porphyrin complex, FeIII(TPP)(O2 ?-). The temperature dependence of both the electron transfer and O2 binding equilibrium constants has been determined. Kinetic studies over a range of concentrations and temperatures show that the catalyst resting state changes during the course of each catalytic run, necessitating the use of global kinetic modeling to extract rate constants and kinetic barriers. The rate-determining step in oxygen reduction is the protonation of FeIII(TPP)(O2 ?-) by pTsOH, which proceeds with a substantial kinetic barrier. Computational studies indicate that this barrier for proton transfer arises from an unfavorable preassociation of the proton donor with the superoxide adduct and a transition state that requires significant desolvation of the proton donor. Together, these results are the first example of oxygen reduction by iron tetraphenylporphyrin where the pre-equilibria among ferric, ferrous, and ferric-superoxide intermediates have been quantified under catalytic conditions. This work gives a generalizable model for the mechanism of iron porphyrin-catalyzed ORR and provides an unusually complete mechanistic study of an ORR reaction. More broadly, this study also highlights the kinetic challenges for proton transfer to catalytic intermediates in organic media.
- Pegis, Michael L.,Martin, Daniel J.,Wise, Catherine F.,Brezny, Anna C.,Johnson, Samantha I.,Johnson, Lewis E.,Kumar, Neeraj,Raugei, Simone,Mayer, James M.
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- Synthesis and Electrocatalytic CO2Reduction Activity of an Iron Porphyrin Complex Bearing a Hydroquinone Moiety
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An iron porphyrin complex bearing a hydroquinone moiety at the meso position was newly designed and synthesized. Electrochemical analysis revealed that it catalyzes CO2reduction at a lower overpotential compared with an iron complex without a hydroquinone moiety. Experimental and theoretical investigation suggested that a hydroquinone moiety at the meso position stabilizes the coordination bond between the metal center and CO2via a hydrogen bond interaction with the latter in the secondary coordination sphere.
- Imai, Maho,Kondo, Mio,Kosugi, Kento,Masaoka, Shigeyuki
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supporting information
p. 224 - 228
(2022/03/07)
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- Method for synthesizing trivalent tetraaryl ferriporphyrin from pyrrole, aromatic aldehyde and bivalent ferric salt
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The invention discloses a method for synthesizing trivalent tetraaryl ferriporphyrin from pyrrole, aromatic aldehyde and bivalent ferric salt. The method comprises the following steps: refluxing aromatic aldehyde, pyrrole and ferrous chloride in a DMF solvent under the catalysis of anhydrous aluminum trichloride to synthesize trivalent tetraaryl ferriporphyrin in one step. The reaction process comprises the following steps: sequentially adding anhydrous aluminum trichloride, aryl aldehyde, pyrrole and ferrite into DMF (Dimethyl Formamide) while stirring, introducing nitrogen, carrying out heating reflux reaction for 0.5 hour, removing the nitrogen, continuing to heat for a certain period of time, stopping the reaction, performing cooling, standing overnight near 273K, and carrying out suction filtration to obtain ferroporphyrin. According to the method, aromatic aldehyde, pyrrole and ferrous chloride are directly used as raw materials, porphin is not needed, and strongly corrosive organic acid is not used as a solvent; high-purity tetraaryl ferriporphyrin is obtained at a high yield under the condition that a complex separation means is not needed, and industrial production is easyto achieve.
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Paragraph 0028-0029
(2020/08/17)
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- Synthetic Iron Porphyrins for Probing the Differences in the Electronic Structures of Heme a3, Heme d, and Heme d1
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A variety of heme derivatives are pervasive in nature, having different architectures that are complementary to their function. Herein, we report the synthesis of a series of iron porphyrinoids, which bear electron-withdrawing groups and/or are saturated at the β-pyrrolic position, mimicking the structural variation of naturally occurring hemes. The effects of the aforementioned factors were systematically studied using a combination of electrochemistry, spectroscopy, and theoretical calculations with the carbon monoxide (CO) and nitric oxide (NO) adducts of these iron porphyinoids. The reduction potentials of iron porphyrinoids vary over several hundreds of millivolts, and the X-O (X = C, N) vibrations of the adducts vary over 10-15 cm-1. Density functional theory calculations indicate that the presence of electron-withdrawing groups and saturation of the pyrrole ring lowers the π?-acceptor orbital energies of the macrocycle, which, in turn, attenuates the bonding of iron to CO and NO. A hypothesis has been presented as to why cytochrome c containing nitrite reductases and cytochrome cd1 containing nitrite reductases follow different mechanistic pathways of nitrite reduction. This study also helps to rationalize the choice of heme a3 and not the most abundant heme b cofactor in cytochrome c oxidase.
- Amanullah, Sk,Saha, Paramita,Saha, Rajat,Dey, Abhishek
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p. 152 - 164
(2019/01/08)
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- Remote ion-pair interactions in Fe-porphyrin-based molecular catalysts for the hydrogen evolution reaction
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The environmentally benign production of clean energy is extremely important for the sustainable progress of our society. In this respect, dihydrogen (H2) has been considered in the last decades as an efficient energy carrier and much effort has been directed to the hydrogen evolution reaction (HER). Herein, we report on the efficiency of iron-based 5,10,15,20-tetraphenylporphyrins containing carboxylate groups in different positions (ortho, meta and para of the meso-substituted aryl groups of the porphyrin backbone) as molecular catalysts for the HER. The iron-based porphyrin containing the carboxylic acids in the ortho position was found completely inactive in the HER. Furthermore, besides stereoelectronic control, the subtle differences observed in the cyclic voltammograms (CV) as well as those associated with the electrocatalytic activity might involve a previously neglected ion-pair interaction between the carboxylate groups of the porphyrin scaffold and the chloride anions belonging to the proton source, which highlights the relevance of ion-pair contacts remote from the active center for this type of catalytic system.
- Kasemthaveechok, Sitthichok,Fabre, Bruno,Loget, Gabriel,Gramage-Doria, Rafael
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p. 1301 - 1308
(2019/03/12)
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- Cobalt(II)-based Metalloradical Activation of 2-(Diazomethyl)pyridines for Radical Transannulation and Cyclopropanation
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A new catalytic method for the denitrogenative transannulation/cyclopropanation of in-situ-generated 2-(diazomethyl)pyridines is described using a cobalt-catalyzed radical-activation mechanism. The method takes advantage of the inherent properties of a CoIII-carbene radical intermediate and is the first report of denitrogenative transannulation/cyclopropanation by a radical-activation mechanism, which is supported by various control experiments. The synthetic benefits of the metalloradical approach are showcased with a short total synthesis of (±)-monomorine.
- Roy, Satyajit,Das, Sandip Kumar,Chattopadhyay, Buddhadeb
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supporting information
p. 2238 - 2243
(2018/02/19)
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- Iron-based metalloporphyrins as efficient catalysts for aerobic oxidation of biomass derived furfural into maleic acid
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A series of porphyrin type catalysts with the metal active sites of Fe were prepared and investigated in aerobic oxidation of biomass-based furfural to maleic acid (MAD) in aqueous phase. The catalytic performance of meso-tetrakis(4-bromophenyl)porphyrin iron (III) chloride (FeT(p-Br)PPCl) immobilized on different supports was evaluated. It was interesting to find that the catalytic activity varied with the supports and followed the trend: FeT(p-Br)PPCl/SBA–15 > FeT(p-Br)PPCl/meso-ZSM–5 > FeT(p-Br)PPCl/MCM-41. The effect of reaction conditions were discussed in detail over FeT(p-Br)PPCl/SBA-15 catalyst, and 56.1% yield and 73.8% selectivity of MAD were obtained from renewable furfural under the optimal conditions. Moreover, the FeT(p-Br)PPCl/SBA-15 catalyst could be reused five times without a significant decrease of activity in recycling examinations.
- Xie, Yongdi,Huang, Yi,Wu, Chunyan,Yuan, Wenwen,Xia, Yongmei,Liu, Xiang,Wang, Haijun
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- Biomimetic Cleavage of Aryl–Nitrogen Bonds in N-Arylazoles Catalyzed by Metalloporphyrins
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The cleavage of C–N single bonds of N-containing compounds provides either an excellent nitrogen source or an excellent carbon source. In this study, an efficient metalloporphyrins/H2O2 cleavage of C–N bonds of arylpyrazoles was investigated. The effects of different factors, including different catalysts, catalyst dosages, H2O2 dosages, reaction temperature and reaction time were studied. The experimental results showed that the optimal catalyst was FeTPPCl, and the yield of pyrazole derivatives could reach up to 12.3%, which was fourfold higher than hemin catalyzed reaction and closed to ceric ammonium nitrate catalyzed reaction, respectively. Compared with transition-metal-catalyzed and strong-oxidization cleavage of C–N bonds, this protocol is characterized by environmentally-friendly, stable, mild reaction conditions and simplified operation procedures. Graphical Abstract: [Figure not available: see fulltext.].
- Yu, Zongjiang,Zhai, Guoqing,Xian, Mo,Lu, Ming,Wang, Pengcheng,Jiang, Tao,Xu, Chao,Sun, Weizhi
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p. 2636 - 2642
(2018/06/20)
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- Cis -Decalin oxidation as a stereochemical probe of in-MOF versus on-MOF catalysis
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Development of catalyst-controlled C-H hydroxylation could provide direct access to valuable synthetic targets, such as primary metabolites. Here, we report a new family of porous materials, comprised of 2-dimensional metalloporphyrin layers and flexible aliphatic linkers, and demonstrate C-H hydroxylation activity. We demonstrate that the stereochemistry of cis-decalin oxidation provides a useful tool for differentiating catalysis in from catalysis on porous materials, which is critical to leveraging the potential of porous materials for catalyst-controlled oxidation chemistry.
- Cardenal, Ashley D.,Jeong Park, Hye,Chalker, Cody J.,Ortiz, Kacey G.,Powers, David C.
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supporting information
p. 7377 - 7380
(2017/07/11)
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- Catalytic Aerobic Oxidation of Biomass-based Furfural into Maleic Acid in Aqueous Phase with Metalloporphyrin Catalysts
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Catalytic oxidation of renewable furfural into valuable maleic acid in aqueous solutions using metalloporphyrin catalysts was investigated for the first time. The synthesized catalysts were characterized by FT-IR, UV–vis, 1H NMR, elemental analysis, and TGA. The catalysts varied in metal active sites and functional groups, which had different effects on their catalytic activity. Furthermore, the effects of temperatures, reaction time, catalyst loading, and oxygen pressure were studied in detail. Maleic acid could be achieved in 44% yield by using FeT(p-Cl)PPCl as catalyst under optimal conditions. Finally, FeT(p-Cl)PPCl could be reused in five consecutive runs without a significant loss of activity.
- Huang, Yi,Wu, Chunyan,Yuan, Wenwen,Xia, Yongmei,Liu, Xiang,Yang, Huamei,Wang, Haijun
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p. 786 - 794
(2017/07/24)
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- Metalloporphyrin-Based Hypercrosslinked Polymers Catalyze Hetero-Diels–Alder Reactions of Unactivated Aldehydes with Simple Dienes: A Fascinating Strategy for the Construction of Heterogeneous Catalysts
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We describe a novel and intriguing strategy for the construction of efficient heterogeneous catalysts by hypercrosslinking catalyst molecules in a one-pot Friedel–Crafts alkylation reaction. The new hypercrosslinked polymers (HCPs) as porous solid catalysts exhibit the combined advantages of homogeneous and heterogeneous catalysis, owing to their high surface area, good stability, and tailoring of catalytic centers on the frameworks. Indeed, a new class of metalloporphyrin-based HCPs were successfully synthesized using modified iron(III) porphyrin complexes as building blocks, and the resulting networks were found to be excellent recyclable heterogeneous catalysts for the hetero-Diels–Alder reaction of unactivated aldehydes with 1,3-dienes. Moreover, this new strategy showed wide adaptability, and many kinds of homogeneous-like solid-based catalysts with high catalytic performance and excellent recyclability were also constructed.
- Dou, Zhiyu,Xu, Li,Zhi, Yongfeng,Zhang, Yuwei,Xia, Hong,Mu, Ying,Liu, Xiaoming
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supporting information
p. 9919 - 9922
(2016/07/19)
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- Influence of substituents in meso-aryl groups of iron μ-oxo porphyrins on their catalytic activity in the oxidation of cycloalkanes
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The aim of this work was to study the effect of substituents on the catalytic activity of iron μ-oxo porphyrins in oxidation of cycloalkanes. Electron-donating or electron-withdrawing substituents were introduced in meso-aryl groups of iron μ-oxo porphyrins. An important part of the work was the characterization of the catalysts, in particular their redox properties. Catalytic performance and selectivity were evaluated using cyclopentane, cyclohexane, and cyclooctane as model compounds. It was shown that not only electron-withdrawing but also electron-donating substituents improved the catalytic performance of iron μ-oxo complexes. Moreover, catalytic activity of iron μ-oxo porphyrins with electron-withdrawing substituents correlated with the half-wave potential E1/2while the catalytic activity of iron μ-oxo porphyrins with electron-donating substituents increased with the decrease of reduction potential ERED.
- Tabor, Edyta,Po?towicz, Jan,Pamin, Katarzyna,Bas?g, Sylwia,Kubiak, W?adys?aw
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p. 342 - 349
(2016/10/09)
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- Synthesis of pure iron(II) mesotetraphenylchlorin complexes via a versatile general method of iron insertion into chlorins
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An original synthesis of pure (tetraphenylchlorinato)iron(III) chloride (1) is reported. Insertion of iron is achieved using 1.2 equivalents of cadmium acetate in DMF at 110 °C, followed by a transmetallation reaction (in situ) using 8 equivalents of iron(II) chloride tetrahydrate in acetone at 60 °C. The 1H NMR shifts at 25 °C of the pyrrole protons varied from 60 to 100 ppm. The absence of the signal at 80 ppm related to undesired (tetraphenylporphirinato)iron(III) chloride is a purity criterion and shows the importance of the method used. Reaction of (tetraphenylchlorinato)iron(III) chloride (1) with four equivalents of tert-butyl isocyanide, 2,6-xylyl isocyanide and dimethylphenylphosphine in the presence of zinc amalgam in dichloromethane (DCM) afforded pure FeII(TPC)(t-BuNC)2 (2), FeII(TPC)(2,6-xylylNC)2 (3) and Fe II(TPC)[P(Me)2Ph]2 (4) respectively.
- Kobeissi, Marwan,Cherry, Khalil,Faraj, Mahmoud K.,Simonneaux, Gérard
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- Stereoelectronic effects of the meso-substituents on the catalytic performance of iron(III) meso-tetraarylporphyrins: Pyridyl and N-methylated pyridyl groups compared to phenyl, 4-methoxyphenyl and 4-sulfonatophenyl ones
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The activity of a series of iron(III) meso-tetraarylporphyrins (aryl = phenyl, 4-methoxyphenyl, 4-sulfonatophenyl, 2-pyridyl, 3-pyridyl, 4-pyridyl and N-methyl-pyridyl counterparts) in the catalysis of oxidation reactions of olefins with tetra-n-butylammonium periodate (TBAP) or NaIO4 in the presence of imidazole (ImH) has been studied. While the presence of ImH has no effect on the catalytic activity of the Fe-porphyrins containing pyridyl or N-methylated pyridyl substituents at the meso-positions, the catalytic performance of the other Fe-porphyrins significantly increased by the use of ImH in 5:1 molar ratio with respect to the catalyst. As was observed in the comparison of the Mn-porphyrins with pyridyl substituents, the oxidative stability of FeT(4-py)P(OAc) is remarkably higher than that of FeT(2-py)P(OAc) and FeT(3-py)P(OAc). Also, the same order of relative stability was found in the case of the N-methylated analogues. It is noteworthy that N-methylation of FeT(py)P(OAc) complexes led to the substantial decrease in their oxidative stability. Competitive oxidation of cis- and trans-stilbene, provides indirect evidence for the involvement of high valent Fe-oxo porphyrins as well as periodato iron porphyrins as the active oxidant in reactions catalyzed by the used iron porphyrins. However, the involvement of a high valent iron-oxo porphyrin species is more pronounced in the case of FeTPPS4(OAc), FeT(2-py)P(OAc), FeT(3-py)P(OAc), FeT(4-py)P(OAc) and the N-methylated analogues. Also, an unusual preference of trans-stilbene over cis-stilbene was observed in the competitive epoxidation reaction catalyzed by FeT(3-MePy)P(OAc) and FeT(4-MePy)P(OAc) which cannot be described by the cis/trans isomerization. Furthermore, significant cis/trans isomerization observed upon oxidation of cis-stilbene in the reaction catalyzed by FeT(2-MePy)P(OAc) indicates that steric effects due to the presence of methyl groups at the ortho positions of this complex are of minor importance. On the other hand, large differences were observed in the product distribution for oxidation reactions with TBAO performed in dichloromethane and aqueous solvent. In spite of the lack of close correlation between the catalytic activity of the Fe-porphyrins and the electronic properties of the meso-substituents, in comparison with the corresponding Mn-porphyrins, there is a better correlation between the catalytic activity of the Fe-porphyrins and the electronic effects of the meso-groups.
- Zakavi, Saeed,Mokary Yazdeli, Tahereh
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p. 108 - 115
(2013/02/23)
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- Synthesis, characterization and spectral properties of substituted tetraphenylporphyrin iron chloride complexes
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A series of substituted tetraphenylporphyrin iron chloride complexes [RTPPFe(III)Cl, R=o/p-NO2, o/p-Cl, H, o/p-CH3, o/p-OCH3] were synthesized by a novel universal mixed-solvent method and the spectral properties of free b
- Sun, Zhi-Cheng,She, Yuan-Bin,Zhou, Yang,Song, Xu-Feng,Li, Kai
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experimental part
p. 2960 - 2970
(2011/06/21)
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- Replacement of imidazoles by azide at an iron(III) porphyrin center: Part 1 replacement of N-methylimidazole in bis-(N-methylimidazole) tetraphenylporphyrinato iron(III)
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Addition of tetra-n-butylammonium azide to acetone solutions of the tetraphenylporphyrinato iron(III) complex [Fe(TPP)(MeIm)2] +N-3 formed in situ from the reaction of N-methylimidazole and [Fe(TPP)N3] afforded equilibrium amounts of [Fe(TPP)(MeIm)2]+ and [Fe(TPP)(MeIm)N3]. Equilibrium experiments made using a range of known concentrations of added tetra-n-butylammonium azide and N-methylimidazole using stopped-flow apparatus gave an estimate of about 50 for the equilibrium constant for the formation of [Fe(TPP)(MeIm)N3] from the addition of azide to [Fe(TPP)(MeIm) 2]+. Kinetic studies indicated that the substitution of azide ion by N-methylimidazole is a dissociative process, and the results were interpreted using a stationary state approach in which [Fe(TPP)(MeIm)] + was the transient intermediate that discriminated in favor of the reaction with azide as opposed to the reaction with N-methylimidazole by about a factor of two. Loss of N-methylimidazole from [Fe(TPP)(MeIm)2] + is at least 50 times faster than that from the product [Fe(TPP)(MeIm)N3]. Using calculated values of free azide concentrations from experimentally determined ion-pair formation constants led to success in rationalizing results obtained under different conditions.
- Jones, John G.,McKnight, John,Twigg, Martyn V.
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experimental part
p. 2766 - 2778
(2010/12/25)
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- Synthesis and characterization of monomer and dimer complexes of porphyrin iron(III) with bridging phenylcyanamide ligands
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Several new mono and dinuclear complexes of [(P)FeIII(L)], in which P is the dianion of tetraphenylporphyrin(TPP) and tetramesitylporphyrin(TMP) and L is the monoanion of 4-azo(phenylcyanamido)benzene (apc) (1) and (2) or dianion 1,4-di cyanami
- MohammadNezhad, Jafar,Safari, Nasser
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p. 2782 - 2787
(2009/09/24)
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- Extreme rate acceleration by axial thiolate coordination on the isomerization of endoperoxide catalyzed by iron porphyrin
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(Chemical Equation Presented) A coordinated effort: The isomerization mechanism of prostaglandin H2 (PGH2), which is catalytically isomerized to prostacyclin or thromboxane A2 by cytochrome P450s, was investigated using a hemethiolate complex and an endoperoxide. Isomerization of endoperoxides proceeded very rapidly with this complex, whereas imidazole- or chloride-ligated heme had slight or no catalytic activity (see scheme).
- Yamane, Takehiro,Makino, Kohei,Umezawa, Naoki,Kato, Nobuki,Higuchi, Tsunehiko
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supporting information; experimental part
p. 6438 - 6440
(2009/03/11)
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- Approaches to the synthesis of heterogenised metalloporphyrins: Application of new materials as electrocatalysts for oxygen reduction
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Porphyrins and different metalloporphyrins have been synthesised and heterogenised on robust inorganic solids such as silica gel, purely siliceous MCM-41, and delaminated zeolites ITQ-2 and ITQ-6. Two different strategies for preparation of these catalysts have been explored, mainly based on immobilisation of a functionalisated porphyrin (route A) or heterogenisation of an aromatic aldehyde and consecutive porphyrin formation (route B). Route A yields stable materials and allows introduction of a larger quantity of metalloporphyrin onto the support (contents ranged from 0.3 to 0.4 mmol g -1) whereas route B was unsuccessful and no evidence was found to support the porphyrin formation. A multitechnique approach is employed for characterisation of samples and their catalytic behaviour has been tested in the electroreduction of oxygen. A cyclic voltammetry investigation, at varying scan rate, was carried out in an attempt to elucidate the net reaction for the oxygen reduction. The synthesised metalloporphyrins are active for electrocatalytic reduction of oxygen by a two-electron mechanism, producing hydrogen peroxide. The comparison between homogeneous and heterogenised catalysts confirms that heterogenisation avoids the catalyst desorption (lost of activity) from the electrode. Catalytic activity is directly related with the content of metalloporphyrin in heterogenised materials that are addressable electronically.
- Fuerte,Corma,Iglesias,Morales,Sánchez
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p. 109 - 117
(2008/10/09)
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- A green process for oxidation of p-nitrotoluene catalyzed by metalloporphyrins under mild conditions
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A novel synthetic technology of p-nitrobenzoic acid has been investigated with dioxygen by using metalloporphyrins RTPP-MIIICl (M = Fe, Co, Mn) as biomimetic catalysts. Oxidation of p-nitrotoluene to p-nitrobenzoic acid under 2.0 MPa of O2 in the presence of a microamount of metalloporphyrins (RTPP-MIIICl) at 55 °C was achieved with the highest (up to 90.4%) yield. Further research results show that the catalytic activities were relative to the nature of the substituted groups and the central metal ions of metalloporphyrins. For the metalloporphyrins with the same center metal ions, the greater the electron-withdrawing degree of groups in the porphyrin ring, the higher the catalytic activities of the metalloporphyrins. The catalytic activities for metalloporphyrins with different center metal ions followed the order RTPPMn IIICl > RTPP Fe IIICl > RTPP Co IIICl.
- Wang, Lanzhi,She, Yuanbin,Zhong, Rugang,Ji, Hongbing,Zhang, Yanhui,Song, Xufeng
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p. 757 - 761
(2012/12/22)
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- Olefin oxidation with dioxygen catalyzed by porphyrins and phthalocyanines intercalated in α-zirconium phosphate
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Oxidation of cyclohexene and cis-stilbene with dioxygen in presence of metal phthalocyanines or metal tetraphenylporphyrins complexes intercalated in α-zirconium phosphate and isobutyraldehyde were studied. The degradation of free metal complexes in solution in the reaction media was verified. It was observed that the matrix protects the metal complexes from degradation and the activity of the catalytic system is preserved. Oxidation of cyclohexene with intercalated complexes gave epoxide as the predominant product, while allylic oxidation products were obtained in smaller proportion and the product distributions depended on the identity of the individual metal complexes. Since the addition of a free radical inhibitor stops the reaction, a free radical mechanism should be present. Oxidation of cis-stilbene with intercalated metal complexes gives different ratios of cis- to trans-stilbene oxide and of benzaldehyde which depend on the intercalated metal complex, suggesting that in addition to the free radicals there is another active oxidizing agent.
- Ni?o, Martha E,Giraldo, Sonia A,Páez-Mozo, Edgar A
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p. 139 - 151
(2008/10/08)
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- Photoluminescent properties of cadmium selenide in contact with solutions and films of metalloporphyrins: Nitric oxide sensing and evidence for the aversion of an analyte to a buried semiconductor-film interface
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The band-edge photoluminescence (PL) intensity of etched n-CdSe single crystals is quenched reversibly by adsorption of the trivalent metalloporphyrins, MTPPCl (TPP = tetraphenylporphyrin; M = Mn, Fe, Co) in nitrogen-saturated methylene chloride solution. The PL responses are concentration dependent and can be fit to the Langmuir adsorption isotherm model to yield binding constants of ~103-104 M-1. The MTPPCl compounds react irreversibly with NO in solution to form nitrosyl adducts, and these compounds reversibly enhance the CdSe PL intensity when adsorbed onto the semiconductor surface, also with binding constants of ~103-104 M-1. Films of MTPPCl were prepared on CdSe substrates by solvent evaporation. These coatings serve as transducers for NO detection: while the bare CdSe surface shows no response to NO gas relative to N2, the coated surfaces reversibly enhance the PL intensity (CoTPPCl) or quench it (MnTPPCl and FeTPPCl), with binding constants on the order of ~1 atm-1. In contrast to the PL results, which are particularly sensitive to the semiconductor-film interface, electronic and IR spectral changes of the bulk film induced by NO binding were irreversible. The UV-vis and IR spectra could be spectroscopically mimicked by preformed nitrosyl adduct films that were prepared by solvent evaporation of MTPPCl (M = Co, Fe) and MTPP (M = Co) solutions that had been exposed to NO. These films, however, lack transduction capability, as the PL intensity is the same in NO and N2 ambients. For the films prepared from FeTPPCl and CoTPPCl, the saturation of IR and UV-vis spectral changes occurs at NO pressures at least 10-fold lower than observed for PL changes. These results indicate that NO has a strong aversion to binding at the semiconductor-film interface as opposed to the bulk film environment. Steric and electronic contributions to these observed effects are discussed.
- Ivanisevic, Albena,Reynolds, Mark F.,Burstyn, Judith N.,Ellis, Arthur B.
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p. 3731 - 3738
(2007/10/03)
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- Electroreduction of μ-oxo iron(III) porphyrins adsorbed on an electrode leading to a cofacial geometry for the iron(II) complex: Unexpected active site for the catalytic reduction of O2 to H2O
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Acidification of a solution of (μ-oxo)bis[(5,10,15,20- tetraphenylporphyrinato)iron(III)] ([{Fe(tpp)}2O], II) in CH2Cl2 produced equimolar amounts of a hydroxoiron(III) complex [(tpp)Fe(III)(OH)] (III) and an iron(III) complex [(tpp)Fe(III)(ClO4)] (IV). The complex IV was isolated as a perchlorate salt, which crystallized in the triclinic space group P1 (2); a = 11.909(3), b = 19.603(4), c = 10.494(3) A, α = 95.74(2)°, β = 107.91(2)°, γ = 89.14(2)°, V = 2319.1(9) A3, Z = 2, D(calc)= 1.328 g cm-3, μ(Mo Kα) = 4.35 cm-1, final R = 0.055 and R(w) = 0.050. The crystal structure of IV revealed that ClO4- is coordinated to the iron atom, which may be driven by the preference of iron(III) to be five coordinate rather than four coordinate. Reduction of the complex II in the presence of acid by electrolysis and/or by a reducing agent, such as sodium dithionite, under argon produced [Fe(II)(tpp)]. The addition of O2 to a solution of [Fe(tpp)] in acidic CH2Cl2 in the presence of an equimolar amount of the reducing agent produced the complex III. When the complex II was adsorbed on an electrode surface and placed in aqueous acidic electrolyte solutions, electroreduction of the adsorbate proceeded according to the half- reaction: [{Fe(tpp)}2O] +2H++2e-→2[Fe(tpp)]+H2O, at 0.031-0.059 pH V (vs. SCE, pH > 1.0). Based on these results, oxo-bridged iron(III) porphyrin dimers were used as electrocatalysts for the reduction of O2. The catalytic reduction of O2 proceeded at potentials in the vicinity of those for II. As a whole, the proportion of H2O as the product increased from 50% for adsorbed [(tpp)Fe(III)Cl] to > 90% for the adsorbed dimer. Thus, electroreduction of the dimer adsorbed on a carbon electrode immersed in aqueous acid produced two solid state, cofacially fixed iron(II) porphyrin molecules: [PFe(III)OFe(III)P](ad)+2H++2e-→[PFe(II) Fe(II)P](ad)+H2O (P = porphyrin dianion). Coordination of molecular oxygen to the adjacent two iron(II) centers under acidic conditions allowed formation of O2-bridged iron(III) porphyrin [PFe(III)(O2) Fe(III)P](ad) at the electrode surface. Electroreduction of the adsorbate under acidic conditions produced H2O and allowed the reformation of [PFe(II) Fe(II)P](ad). The implication is that the electroreduction of the adsorbed oxo-bridged dimer gives a cofacial geometry for PFe(II) on the electrode, facilitating the coordination and subsequent splitting of O2.
- Oyaizu, Kenichi,Haryono, Agus,Natori, Junichiro,Shinoda, Hiroshi,Tsuchida, Eishun
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p. 1153 - 1163
(2007/10/03)
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- Resonance Raman spectroscopic detection of steric-induced distortions of axial ligand binding for dioxygen adducts of superstructured cobalt-porphyrin complexes
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Resonance Raman studies are carried out for the O2 adducts of superstructured "jellyfish" cobalt-porphyrin complexes with several trans-axial ligands, namely, pyridine, 3,5-lutidine, and imidazole as well as several of their deuteriated analogues. Two superstructured, bis-strapped porphyrins, having either short (9 carbon atoms) or long (12 carbon atoms) strap lengths, are employed along with sterically relaxed (non-strapped) porphyrins. It is found that the short-strap derivative induces distortion of the bound ligands while the long-strap analogue permits normal, unencumbered binding. While the distortion of the trans-axial ligand does not significantly affect the Co-O2 linkage, as judged by the constancy of the inherent frequency of ν(O-O), significant shifts of the ligand internal modes give rise to substantially altered spectra as a result of variations in the strength of vibrational coupling of the ν(O-O) with internal modes of the trans-axial ligand.
- Proniewicz, Leonard M.,Bruha, Alan,Nakamoto, Kazuo,Uemori, Yoshio,Kyuno, Eishin,Kincaid, James R.
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p. 9100 - 9104
(2007/10/02)
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- Identification of High-Valent Fluoroiron Porphyrin Intermediates Associated with the Electrocatalytic Functionalization of Hydrocarbons
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The difluoroiron(III) tetraphenylporphyrin complex undergoes a one-electron oxidation at 0.68 V (SCE) in contrast with values of 1.1 V measured for the monofluoroiron(III) porphyrin and the other five-coordinate iron(III) porphyrin complexes.Cyclic voltammetric oxidation of the difluoroiron(III) species in dichloromethane solution is quasi-reversible as a consequence of an EC mechanism.Reversible waves are favored at high scan rates and lower temperatures.Increased water content serves to make the oxidative cyclic voltammetric process irreversible presumably due to a disproportionation process.In the presence of added olefin substrates, this EC process permits efficient electrocatalytic oxidation to the epoxide, allylic alcohol, and enone.Tertiary carbon units are converted to the corresponding alcohol.Utilization of fluoride ion permits generation and low-temperature spectroscopic identification of a highly oxidized iron porphyrin species.The high-valent complex is produced at -78 deg C through addition of m-chloroperbenzoic acid to monofluoroiron(III) tetraarylporphyrins or by fluoride ion promoted disproportionation of the dication radical μ-oxo dimeric iron(III) porphyrin derivative.The oxidized iron porphyrin species is competent to effect olefin epoxidation at -78 deg C.Low-temperature 1H and 2H NMR spectroscopies demonstrate the porphyrin ?-cation radical nature of the high-valent species, in that porphyrin phenyl resonances are drastically shifted in alternating upfield and downfield directions.The electron spin resonance spectrum is consistent with an S = 3/2 ground state, and the high-valent intermediate is assigned a tentative fluorooxoiron(IV) porphyrin ?-cation radical formulation.
- Hickman, David L.,Nanthakumar, Alaganandan,Goff, Harold M.
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p. 6384 - 6390
(2007/10/02)
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- Oxochromium compounds. 1. Synthesis and properties of μ-oxo chromium-iron porphyrin and phthalocyanine compounds
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The reaction between CrIVO(P) and FeII(P′) leads to the formation of μ-oxo heterobinuclear complexes (P)CrOFe(P′) where P and P′ represent dianions of porphyrins that may be the same or different. [Abbreviations for the dianions of 5,10,15,20-tetraarylporphyrins: TPP, tetraphenylporphyrin; TTP, tetra-p-tolylporphyrin; TMP, tetrakis(p-methoxyphenyl)porphyrin; TFP, tetrakis(p-fluorophenyl)porphyrin; TCP, tetrakis(p-chlorophenyl)porphyrin; TXP, tetra-3,5-xylylporphyrin; OEP, the dianion of 2,3,7,8,12,13,17,18-octaethylporphyrin; Pc, the dianion of the phthalocyanine molecule.] The complexes react with heterocyclic Lewis bases, and these coordinate to Cr only. The visible, infrared, 1H NMR, and Mo?ssbauer spectra are reported for the compounds. The variation of magnetic susceptibility with temperature down to 4.2 K is interpreted in terms of strong antiferromagnetic coupling between Cr(III) (S = 3/2) and Fe(III) (S = 5/2) centers with J values in the range -130 to -150 cm-1. Zero field splitting effects are important at low temperatures. The reaction of CrO(TPP) with FeII(Pc) forms an analogous μ-oxo complex having porphyrin and phthalocyanine groups attached to Cr(III) and Fe(III), respectively.
- Liston, David J.,Kennedy, Brendan J.,Murray, Keith S.,West, Bruce O.
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p. 1561 - 1567
(2008/10/08)
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- COMPLEXES DE LA FERROTETRAPHENYLPORPHYRINE AVEC DES HALOGENOALKYLCARBENES: Fe
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Stable carbeneiron(II) complexes with halocarbenes having an alkyl group (CH3 or C(OH)R'R'') have been isolated and their structures established by 1H and 13C NMR, IR and mass spectroscopy.Their ability to coordinate ligands such as alcohols or pyridine i
- Guerin, Philippe,Battioni, Jean-Paul,Chottard, Jean-Claude,Mansuy, Daniel
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p. 201 - 209
(2007/10/02)
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