81278-77-5Relevant academic research and scientific papers
Photoactivation of molecular oxygen by an iron(III) porphyrin with a magnesium aluminum layered double hydroxide for the aerobic epoxidation of cyclohexene
Teramura, Kentaro,Tsuneoka, Hideo,Ogura, Kentaro,Sugimoto, Takashi,Shishido, Tetsuya,Tanaka, Tsunehiro
, p. 2276 - 2281 (2014/08/18)
The photocatalytic aerobic epoxidation of cyclohexene proceeded under visible-light irradiation only if 5,10,15,20tetrakis(pentafluorophenyl)porphyrin iron(III) chloride ([FeIII(TPFPP)Cl]) was combined with Mg-Al layered double hydroxide (Mg-Al LDH) as a solid base in chloroform. The OH groups in the Mg-Al LDH exchanged with the axial Cl ligands in [Fe III(TPFPP)Cl] to afford [FeIII(TPFPP)OH], which functioned photocatalytically in the presence of Mg-Al LDH but was inactive in its absence. The band in the action spectrum agreed well with the Soret band in the UV/Vis absorption spectrum of [FeIII(TPFPP)OH]. The spectral changes indicated the reduction of [FeIII(TPFPP)OH] to [Fe II(TPFPP)] under visible-light irradiation, which in turn activates O2 that could be used for the epoxidation of cyclohexene.
Hydrogen atom abstraction and hydride transfer reactions by iron(IV)-oxo porphyrins
Jeong, Yu Jin,Kang, Yaeun,Han, Ah-Rim,Lee, Yong-Min,Kotani, Hiroaki,Fukuzumi, Shunichi,Nam, Wonwoo
, p. 7321 - 7324 (2009/04/13)
(Chemical Equation Presented) True identity revealed: The C-H bond activation of alkyl aromatics by synthetic iron(IV)-oxo porphyrin species and the hydride transfer of NADH analogues to them occur through H-atom abstraction and proton-coupled electron-transfer mechanisms, respectively. Mechanistic studies revealed that iron(IV)-oxo porphyrin π, not iron(IV)-oxo porphyrin pradical cations, are the true oxidant.
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.
Models of nitric oxide synthase: Iron(III) porphyrin-catalyzed oxidation of fluorenone oxime to nitric oxide and fluorenone
Wang, Charles C.-Y.,Ho, Douglas M.,Groves, John T.
, p. 12094 - 12103 (2008/10/08)
Nitric oxide synthase (NOS) is a heme-containing monoxygenase that catalyzes the oxidation of L-arginine to L-citrulline and NO in two steps. In the second step of the NOS reaction, citrulline and NO are generated from the heme-catalyzed 3-electron oxidation of L-N-hydroxyarginine. To model this unusual reaction, iron porphyrin-catalyzed oxygenations of oximes with O2 were investigated. The oxidation of fluorenone oxime and a stoichiometric amount of hydroxoiron(III) porphyrin (Fe(OH)P, P = TMP and TPFPP) with O2 in benzene generated Fe(NO)P, fluorenone, and O-(9-nitro-9-fluorenyl)fluorenone oxime. The X-ray crystal structure of the oxime ether product suggests that it originated from the dimerization of the fluorenyl iminoxy radicals. Detailed analysis of this reaction showed that the oxime reacted first with Fe(OH)P to generate a 5-coordinate, high-spin oximatoiron(III) porphyrin species [Fe(oximate)P]. The X-ray crystal structure of oximatoiron(III) tetrakis(2,6-dichlorophenyl)porphyrin [Fe(oximate)TDCPP] showed that the oximate ligand was monodentate, O-bound to Fe(III)P. The aerobic oxidation of Fe(oximate)P followed the characteristic kinetics of a metalloporphyrin- catalyzed radical-type autoxidation. O2 surrogates, the π-acids NO and CO, induced the homolysis of Fe(oximate)P to generate Fe(NO)P or Fe(CO)P and the iminoxy radical, implicating a similar reaction mode for O2 with Fe(oximate)P. Fe(oximate)TMP reacted with 18O2 to generate predominantly 18O-labeled fluorenone (75% yield), while the reaction conducted under 16O2 and H218O generated only 16O-labeled fluorenone. This reaction is proposed to proceed via an Fe-O bond homolysis of Fe(oximate)TMP followed by O2 insertion to generate 9-nitroso-9-fluorenylperoxyFe(III)TMP, which decomposes via an O-O bond homolysis to generate NO, fluorenone, and oxoFe(IV)P. The implications of this system for the NOS reaction mechanism are discussed.
(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.
Reduction of III(tfpp)Cl> by Azaferrocene. The Crystal Structure of II(tfpp)2>
Zakrzewski, Janusz,Cesario, Michele,Guilhem, Jean,Giannotti, Charles
, p. 3059 - 3060 (2007/10/02)
Azaferrocene reacts with chloroiron(III) to give a low-spin iron(II) porphyrin, II(tfpp)2>, the crystal and molecular structure of which has been determined; while air-stable in the solid state, in solution it loses co-ordinated azaferrocene and (under aerobic conditions) undergoes oxidation to FeIII.
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.
