81245-20-7Relevant academic research and scientific papers
An efficient eco-sustainable oxidative desulfurization process using μ-oxo-bridged Fe(III) complex of meso-tetrakis(pentafluorophenyl)porphyrin
Aguiar, António,Ribeiro, Susana,Silva, André M.N.,Cunha-Silva, Luís,De Castro, Baltazar,Silva, Ana M.G.,Balula, Salete S.
, p. 267 - 274 (2014)
The present work is the first report of using a FeIII dimeric porphyrin as an active and efficient catalyst for the oxidative desulfurization of a multicomponent oil formed by the most refractory sulfur compounds in fuels (dibenzothiophene, DBT, 1-benzothiophene, 1-BT, and 4,6- dimethyldibenzothiophene, 4,6-DMDBT), using the biphasic system model oil/extraction solvent. The binuclear μ-oxodiiron(III) complex of meso-tetrakis(pentafluorophenyl)porphyrin μ-O(FeTPFPP)2, was synthesized and characterized by UV/Vis spectroscopy, mass spectrometry and single-crystal X-ray diffraction. μ-O(FeTPFPP)2 was shown to achieve a complete desulfurization after 2 h when acetonitrile and methanol were used as extraction solvents, in the presence of a residual amount of H 2O2 as oxidant, at room temperature. The catalytic efficiency of the porphyrin was evaluated for each refractory sulfur compound following the order 1-BT > DBT > 4,6-DMDBT. Surprisingly, the porphyrin presents a remarkable catalytic performance for the desulfurization of 1-BT when compared with other catalysts already reported in the literature. Furthermore, the extracting phase containing the porphyrin could be reused in consecutive desulfurization cycles.
Mechanistic studies of (porphinato)iron-catalyzed isobutane oxidation. Comparative studies of three classes of electron-deficient porphyrin catalysts
Moore, Kevin T.,Horvath, Istvan T.,Therien, Michael J.
, p. 3125 - 3139 (2008/10/08)
We report herein a comprehensive study of (porphinato)iron [PFe]-catalyzed isobutane oxidation in which molecular oxygen is utilized as the sole oxidant; these catalytic reactions were carried out and monitored in both autoclave reactors and sapphire NMR tubes. In situ 19F and 13C NMR experiments, coupled with GC analyses and optical spectra obtained from the autoclave reactions have enabled the identification of the predominant porphyrinic species present during PFe-catalyzed oxidation of isobutane. Electron-deficient PFe catalysts based on 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin [(C6F5)4PH2], 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(pentafluorophenyl)porphyrin [Br8(C6F5)4PH2], and 5,10,15,20-tetrakis(heptafluoropropyl)porphyrin [(C3F7)4PH2] macrocycles were examined. The nature and distribution of hydrocarbon oxidation products show that an autoxidation reaction pathway dominates the reaction kinetics, consistent with a radical chain process. For each catalytic system examined, PFe(II) species were shown not to be stable under moderate O2 pressure at 80 °C; in every case, the PFe(II) catalyst precursor was converted quantitatively to high-spin PFe(III) complexes prior to the observation of any hydrocarbon oxidation products. Once catalytic isobutane oxidation is initiated, all reactions are marked by concomitant decomposition of the porphyrin-based catalyst. In situ 17O NMR spectroscopic studies confirm the incorporation of 17O from labeled water into the oxidation products, implicating the involvement of PFe-OH in the catalytic cycle. Importantly, Br8(C6F5)4PFe-based catalysts, which lack macrocycle C-H bonds, do not exhibit augmented stability with respect to analogous catalysts based on (C6F5)4PFe and (C3F7)4PFe species. The data presented are consistent with a hydrocarbon oxidation process in which PFe complexes play dual roles of radical chain initiator, and the species responsible for the catalytic decomposition of organic peroxides. This modified Haber-Weiss reaction scheme provides for the decomposition of tert-butyl hydroperoxide intermediates via reaction with PFe-OH complexes; the PFe(III) species responsible for hydroperoxide decomposition are regenerated by reaction of PFe(II) with dioxygen under these experimental conditions.
(19)F NMR Spectra and Structure of Halogenated Porphyrins
Birnbaum, Eva R.,Hodge, Julia A.,Grinstaff, Mark W.,Schaefer, William P.,Henling, Lawrence,et al.
, p. 3625 - 3632 (2008/10/08)
Fluorine-19 NMR spectra of a series of halogenated porphyrins have beenused to create a spectral library of different types of fluorine splitting patterns for tetrakis(pentafluorophenyl) porphyrins (TFPP) complexed with diamagnetic and paramagnetic metal ions. The paramagnetic shift, line broadening, and fine structure of the resonances from the peripheral pentafluorophenyl rings are dependent on the symmetry and core environment of the porphyrin macrocycles. In combination with crystal structuredata, (19)F NMR helps define the behavior of halogenated porphyrins in solution. Six new crystal structures for TFPP and octahalo-TFPP derivatives are reported: H2TFPP in rhombohedral space group R3-, a = 20.327(4) ?, c = 24.368(5) ?, V = 8720(3) ?**3, Z = 9; ZnTFPP in monoclinic space group P21/C, a = 12.653(4) ?, b = 11.883(5) ?, c = 15.261(2) ?, β = 103.87(2)°, V = 2227.6(13) ?**3, Z =2; CuTFPP in rhombohedral space group R3-, a = 20.358(5), c = 24.347(6)?, V = 8739(4) ?**3, Z = 9; H2TFPPCl8 in triclinic space group P1-, a = 11.066(1) ?, b = 14.641(3) ?, c = 14.678(2) ?, α = 88.97(1)°, β = 76.05(1)°, γ = 71.29(1)°, V = 2181.4(6) ?**3, Z = 2; ZnTFPPCl8 in tetragonal space groupP4-21C, a = 19.502(20), c = 10.916(8) ?, V = 4152(6) ?**3, Z = 2; H2TFPPBr8 in monoclinic space group C2, a = 27.634(6) ?, b = 6.926(2) ?, c = 14.844(3) ?, β = 109.64(2)°, V = 2675.8(11) ?**3, Z = 2.
Effect of meso substituents on exchange-coupling interactions in μ-oxo iron(III) porphyrin dimers
Helms, Jeffrey H.,Ter Haar, Leonard W.,Hatfield, William E.,Harris, David L.,Jayaraj,Toney, Glen E.,Gold, Avram,Mewborn, Tabitha D.,Pemberton, Jeanne R.
, p. 2334 - 2337 (2008/10/08)
The μ-oxo iron(III) porphyrin dimers [(TPP)Fe]2O, [(TPP(4-OCH3))Fe]2O, [(TPP(4-CF3))Fe]2O, and [(TPP(F5))Fe]2O (where TPP is meso-tetraphenylporphyrin, TPP(4-OCH3) is meso-tetrakis(4-methoxyphenyl)porphyrin, TPP(4-CF3) is meso-tetrakis(4-(trifluoromethyl)phenyl)porphyrin, and TPP(F5) is meso-tetrakis(pentafluorophenyl)porphyrin) have been studied to determine the effect of peripheral substituents on the porphyrin rings on properties of the molecules. Variable-temperature magnetic susceptibility studies on solid samples yielded the following exchange-coupling constants for the antiferromagnetically coupled iron(III) ions: -146.8 cm-1, [(TPP(4-OCH3))Fe]2O; -135.7 cm-1, [(TPP)Fe]2O; -136.4 cm-1, [(TPP(4-CF3))Fe]2O; -146.9 cm-1, [(TPP(F5))Fe]2O. Variable-temperature 13C NMR studies of dichloromethane solutions yield exchange-coupling constants of -150 cm-1 for [(TPP(4-OCH3))Fe]2O, -145 cm-1 for [(TPP)Fe]2O, and -129 cm-1 for [(TPP(F5))Fe]2O. Raman spectra were collected in the region of the energy of the outer-ring stretching modes found at approximately 1560 cm-1. The position of this band is empirically related to the porphyrin core size, and the data indicate that the porphyrin center-pyrrole nitrogen (Ct-N) distances increase in the order [(TPP(F5))Fe]2O 3))Fe]2O 2O 3))Fe]2O. The data support the hypothesis that the porphyrin ring core size increases as the electron-releasing capability of the peripheral substituent increases. For the para-substituted complexes, increasing core size correlates with stronger axial binding, reflected in stronger antiferromagnetic coupling. The anomalous behavior of [(TPP(F5))Fe]2O may result from distortions caused by steic interactions of the o-fluorines.
