33519-60-7Relevant articles and documents
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
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.
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.
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.
