33519-60-7Relevant academic research and scientific papers
PHOTOREDUCTION OF MANGANESE(III), IRON(III), COBALT(III), AND MOLYBDENUM(V) TETRAPHENYLPORPHYRINS IN 2-METHYLTETRAHYDROFURAN
Imamura, Taira,Jin, Takashi,Suzuki, Toru,Fujimoto, Masatoshi
, p. 847 - 850 (1985)
The central metals in the metallotetraphenylporphyrins with axial halo or pseudohalo ligands, MnIII(tpp)X (tpp = 5,10,15,20-tetraphenylporphinato; X = I, Br, Cl, OAc, NCS), FeIII(tpp)Cl, CoIII(tpp)Cl, and MoVO(t
Solid-state synthesis of molybdenum and tungsten porphyrins and aerial oxidation of coordinated benzenethiolate to benzenesulfonate
Nandi, Goutam,Sarkar, Sabyasachi
, p. 6412 - 6420 (2012)
A new route is developed for the synthesis of molybdenum and tungsten porphyrins using [M(NO)2py2Cl2] (M = Mo, W) as the metal source and TPP (dianion of 5,10,15,20-meso-tetraphenylporphyrin) in the benzoic acid melt. Complexes [MoVO(TPP)(OOCPh)] (1) and [W VO(TPP)(OOCPh)] (2) are isolated in almost quantitative yield. These are characterized by single-crystal X-ray structure analysis, electron paramagnetic resonance, electronic and IR spectroscopy, and magnetic moment measurements. Benzenethiol substitutes for PhCOO- in 1, forming an intermediate thiolato complex that responds to the intramolecular redox reaction across the MoV-SPh bond to yield [MoIVO(TPP)] (3). Under an excess of benzenethiol, PhS- is coordinated to the vacant site in 3, which under aerial oxidation is oxidized to benzenesulfonate to form [Mo VO(TPP)(O3SPh)] (4). 2 undergoes similar aerial oxidation chemistry albeit slowly.
INTERMEDIATE IN THE REACTION OF OXOMOLYBDENUM(V) TETRAPHENYLPORPHYRIN COMPLEX WITH SUPEROXIDE ION IN APROTIC SOLVENTS
Imamura, Taira,Hasegawa, Koichi,Fujimoto, Masatoshi
, p. 705 - 708 (1983)
MoVO(tpp)Br (tpp=meso-tetraphenylporphinato) is reduced by superoxide ion, O2-, to MoIVO(tpp) in 1percent (v/v) DMSO-CH2Cl2 medium at 25 deg C via an intermediate.The intermediate is suggested to be a dioxygen complex and stably exists in the solution at -72 deg C.The oxidation state of the central molybdenum in the intermediate complex reversibly changes with temperature between 4+ at -80 deg C and 5+ at 0 deg C.
Photochemically-induced ligand exchange reactions of ethoxy-oxo-molybdenum(V) tetraphenylporphyrin in chlorinated solvents
Douvas, Antonios M.,Argitis, Panagiotis,Maldotti, Andrea,Coutsolelos, Athanassios G.
, p. 3427 - 3434 (2006)
Photochemically-induced ligand exchange reactions of ethoxy-oxo-molybdenum(V) 5,10,15,20-tetraphenylporphyrin, Mo(V)O(TPP)OEt, under irradiation at the Soret band region, were investigated. The reactions were performed in chlorinated solvents and followed with ultraviolet-visible (UV-vis) spectroscopy, whereas the products were analyzed with Fourier transformed infrared (FTIR) spectroscopy, electron spin resonance (ESR) spectroscopy and gas chromatography (GC). The chloro-oxo(TPP)Mo(V) complex was obtained as the final product, where the chlorine came from the solvent. Nevertheless, these reactions were not photocatalytic, due to the photochemical inertness of the formed chloro-oxo complex, and an excess of ethanol could not initiate a new photocatalytic cycle unless water was added as well, resulting in the formation of a biphasic system. On the other hand, addition of ethanol, water and NaOH to the reaction medium led to the formation of the corresponding oxo Mo(IV) complex. The studied photoassisted reactions of oxo Mo(V) porphyrins appear attractive for possible applications in the detection of chlorinated pollutants in sensing devices, but also for the dechlorination of pollutants upon suitable optimization of processing conditions.
Reversibility in the formation of oxo(peroxo)porphyrinatomolybdenums
Fujihara, Tetsuaki,Hoshiba, Koji,Sasaki, Yoichi,Imamura, Taira
, p. 383 - 389 (2007/10/03)
Reversibility in the formation reaction of a series of the oxo(peroxo)porphyrinatomolybdenums, [Mo(VI)O(tmp)(O2)] 1, [Mo(VI)O(tdcpp)(O2)] 2, [Mo(VI)O(ttp)(O2)] 3, [Mo(VI)O(tdmpp)(O2)] 4, and [Mo(VI)O(tpp)(O2)] 5, was studied. In these dioxygen complexes with various porphyrin rings, two complexes, 2 and 4, were newly prepared by the solid- state reactions of corresponding Mo(IV) complexes with O2. All the complexes were characterized by IR, 1H NMR, and UV- vis spectroscopic measurements. In the reaction of O2 with [Mo(IV)O(tdcpp)] 2r, which has bulky substituents with an electron-withdrawal character, the association rate constant was determined to be 1.2 x 10-2 dm3 mol-1 s-1 in toluene at 20 °C. The value of the rate constant is about one thirtieth of that for [Mo(IV)O(tmp)] 1r, which also has bulky substituents. The result indicates that the electronic effects of the porphyrin rings, which reflect on the redox potentials of the central molybdenum ion, are important in determining kinetic and thermodynamic stability of the dioxygen complexes. All the dioxygen complexes undergo deoxygenation upon photoirradiation to give corresponding [Mo(IV)O(por)]. The redioxy-genation profiles of [Mo(IV)O(por)] in the dark were also significantly affected by the steric bulkiness of the porphyrin ligands. While the bulky porphyrin complexes of 1 and 2 gave full recovery of the dioxygen complexes in the dark, less bulky porphyrin complexes of 3, 4, and 5 undergo some side reactions to Mo(V) species. The rate and extent of the Mo(V) complex formations increase with decreasing steric bulkiness.
Photochemistry of Molybdenum(V) Tetraphenylporphyrin Studied by Laser Flash Photolysis. Light-Induced Homolysis of the Mo-O Bond of Oxoalkoxo- and Oxo(nitrito)molybdenum(V) Tetraphenylporphyrin
Hoshino, Mikio,Iimura, Yasuhiro,Konishi, Shiro
, p. 179 - 185 (2007/10/02)
Photolysis of oxoethoxomolybdenum(V) tetraphenylporphyrin (O=MoV(TPP=OC2H5) in a degassed mixture of 9:1 toluene-ethanol gives rise to the homolysis of the Mo-OC2H5 bond with the yield of 0.03 to produce oxomolybdenum(IV) tetraphenylporphyrin (O=MoIVTPP as a stable product.Oxo(nitrito)molybdenum(V) tetraphenylporphyrin (O=MoV(TPP)ONO) in toluene also undergoes photochemical cleavage of the Mo-ONO bond with the yield 0.28 to give O=MoIVTPP and NO2, which recombine to regenerate O=MoV(TPP)ONO.The quantum yield measurements in the temperature range 300-77 K have shown that the activation energies for the photocleavage of the Mo-OC2H5 and Mo-ONO bonds were 5.4 and 8.0 kcal mol-1, respectively.The lowest excited state of O=MoV(TPP)OC2H5, presumably ascribable to the tripquartet state, is detected by the laser photolysis at 77 K.Because of the fact that the quantum yield for the photocleavage of the Mo-OC2H5 bond upon Q-band irradiation is very low in comparison with those obtained upon irradiation of the Soret and CT bands, it is concluded that the lowest excited state is not responsible for the photocleavage.The photoproduct O=MoIVTPP is found to react with oxygen, resulting in formation of the dioxygen adduct.The adduct gradually changes to the μ-oxo dimer VTPP2O.The structure of the dioxygen adduct is discussed on the basis of optical and ESR measurements.
One-electron-transfer reactions of molybdenum(V) and manganese(III) porphyrins with solvated electrons and solvent radicals in 2-methyltetrahydrofuran
Suzuki,Imamura,Sumiyoshi,Katayama,Fujimoto
, p. 1123 - 1129 (2008/10/08)
The reactions of the six-coordinate molybdenum(V) tetraphenylporphyrins MoVO(TPP)X (X = Br, Cl, F, NCS, N3, OCH3, OC(CH3)3) with solvated electrons and solvent radicals were studied pulse-radiolytically, focusing on effects of the axial ligand X on the rates. Electron-pulse irradiation of the 2-methyltetrahydrofuran (MeTHF) solution dissolving MoVO(TPP)X, which possess neutral charge and are almost all the same size, causes the reduction of the central molybdenum atom, yielding MoIVO(TPP) at room temperature. The constrained complexes [MoIVO(TPP)X]-, formed at 77 K by γ-irradiation, are not stable intermediates in the reactions at room temperature. The reduction proceeds by an outer-sphere mechanism competitively between the reactions with the solvated electron and with the MeTHF neutral radical (MeTHF?). The second-order rate constants of the reactions with the solvated electron and with MeTHF? are in the range of 1010 and 109-108 M-1 s-1, respectively, and depend on the axial ligand X. The orders of the constants are NCS > Br > Cl for the reductions by the solvated electron and NCS > Br > Cl ≈ N3 > F > OCH3 > OC(CH3)3 for the reductions by MeTHF?. The effects of the axial ligand on the redox potentials of MoVO(TPP)X were also studied electrochemically. The redox half-wave potentials of the central molybdenum atom, Mo(V)/Mo(IV), depend on the axial ligand and are in the order Br > Cl > NCS > N3 > F > OCH3 > OC(CH3)3. The orders of magnitude of the radiolytic reaction rate constants almost parallel the order of the anodic shift in the redox potentials of Mo(V)/Mo(IV), as suggested by the Marcus-Hush theory; i.e., the displacement of the axial ligand X mainly reflects on the redox potentials of the central molybdenum that causes the variation in the rates for these outer-sphere redox reactions. Manganese(III) porphyrin systems were also reported in comparison with the MoVO(TPP)X systems.
Facile Preparation of Manganese(II) Tetraphenylporphyrin by the Pyrolysis of Dimethoxomanganese(IV) Tetraphenylporphyrin
Suzuki, Toru,Imamura, Taira,Fujimoto, Masatoshi
, p. 257 - 260 (2007/10/02)
Manganese(II) tetraphenylporphyrin, MnII(tpp) (tpp=meso-tetraphenylporphinato), was afforded by the pyrolysis of MnIV(tpp)(OCH3)2 at ca 180 deg C under 10-4-10-5 Torr (1 Torr ca 133.3 Pa).The pyrolysis of Mosup
Electrochemistry and spectroelectrochemistry of oxo- and peroxomolybdenum porphyrin complexes
Malinski,Hanley,Kadish
, p. 3229 - 3235 (2008/10/08)
The electrochemistry of various oxomolybdenum(IV), -(V), and -(VI) porphyrins is reported in nonaqueous media. The investigated complexes include OMo(TPP), OMo(TPP)(X), O2Mo(TPP), and (O2)2Mo(TmTP), where X = ClO4-, OCH3-, or OH- and where TPP and TmTP are the dianions of tetraphenylporphyrin and tetra-m-tolylporphyrin, respectively. An exact sequence of the individual electron-transfer steps composing the overall redox process of each complex is described, and a comparison between the electrochemistry of the different types of complexes is discussed. Each electrode reaction was monitored by spectroelectrochemistry and by ESR spectroscopy, and on the basis of the electrochemical and spectroscopic data, a self-consistent oxidation-reduction mechanism is presented. The potential for the Mo(V)/Mo(IV) reaction of OMo(TPP)(X) is strongly influenced by the axial ligand X and varies from 0.02 V for X = ClO4- to -0.87 V for X = OCH3-. OMo(TPP)(X) is produced by the one-electron oxidation and coupled oxygen atom transfer of O2Mo(TPP) while OMo(TPP) is generated as the final product in the electroreduction of O2Mo(TPP). This latter reaction involves the addition of two electrons and an ECE mechanism. (O2)2Mo(TmTP) does not lose the bound peroxo groups upon oxidation or reduction. The single one-electron oxidation of (O2)2Mo(TmTP) corresponds to formation of a cation radical. In contrast, the first reduction of (O2)2Mo(TmTP) produces a novel Mo(V) diperoxo complex, which can be further reduced by an additional one-electron-transfer step without loss of the axial peroxo ligand.
Reactions of molybdenum (V) tetraphenylporphyrins with superoxide. Mechanism of the reactions and the characterization of an isolated dioxygen complex
Hasegawa, Koichi,Imamura, Taira,Fujimoto, Masatoshi
, p. 2154 - 2160 (2008/10/08)
The mechanism of the reactions of MoVO(TPP)X (TPP = 5,10,15,20-tetraphenylporphyrin; X = Br, Cl, NCS) with superoxide ion O2- in aprotic solvents under anaerobic conditions has been stoichiometrically elucidated. The complex MoVO(TPP)X is reduced by O2- to MoIVO(TPP) in dichloromethane containing 1% (v/v) dimethyl sulfoxide at 25°C via an intermediate, complex 1. Complex 1 is stable in solution at -80°C but is converted into MoIVO(TPP) at room temperature. Complex 1, a new dioxygen complex of molybdenum tetraphenylporphyrin, was isolated. The chemical formula of complex 1 is ascertained to be [18-crown-6-K][MoVO(TPP)(O22-)] where the dioxygen binds side-on with the electronic configuration of peroxide. The structure and oxidation state of the molybdenum-dioxygen unit in the dioxygen complex are maintained in aprotic media over the temperature range between -80 and -20°C.
