25482-26-2Relevant academic research and scientific papers
Highly selective catalytic preparation of bis(4-oxo-benzo-2-cyclohexen-1-yl) amine from 1-naphthylamine oxidation over metalloporphyrin catalysts by molecular oxygen under air pressure and by hydrogen peroxide
Chen, Tie,Kang, Enhua,Tan, Guiping,Liu, Sijie,Zheng, Shaodan,Yang, Keer,Tong, Shanling,Fang, Chiguang,Xiao, Fengshou,Yan, Yan
, p. 56 - 62 (2006)
In the presence of molecular oxygen or hydrogen peroxide, 1-naphthylamine (1-NA) was catalytically converted into bis(4-oxo-benzo-2-cyclohexen-1-yl) amine (BOBCHA) over metalloporphyrin catalysts through an oxidative-coupling way. UV-vis, IR, NMR, MS, mp determinations and elemental analysis were employed for product characterization. A possible catalytic mechanism based on in situ UV-vis and EPR determinations was proposed. A spectrophotometric method was established for quantitative analysis of the product according to its characteristic absorption at λmax = 465 nm. The influences of reaction conditions, such as solvents, temperature, reaction time, medium alkalinity, as well as species and amount of the catalysts were discussed in detail.
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
Oyaizu, Kenichi,Haryono, Agus,Natori, Junichiro,Shinoda, Hiroshi,Tsuchida, Eishun
, p. 1153 - 1163 (2007/10/03)
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.
Reactivity of the peroxo ligand in metalloporphyrin complexes. Reaction of sulfur dioxide with iron and titanium porphyrin peroxo complexes to give sulfato complexes or sulfate
Miksztal, Andrew R.,Valentine, Joan Selverstone
, p. 3548 - 3552 (2008/10/08)
The reaction of sulfur dioxide with metal-coordinated peroxide to give metal-sulfato complexes has been found in the past to be characteristic of a wide variety of group 8 metal complexes. Similar reactions with metalloporphyrin peroxo complexes have not been reported however. The present paper describes an investigation of such reactions for three different types of metalloporphyrin peroxo complexes: (TPP)Fe-O2-Fe(TPP) (TPP = tetraphenylporphinato) (1), a μ-peroxo ferric porphyrin complex formed by reaction of FeTPP with dioxygen at low temperature; TiP(O2) (P = TPP or OEP; OEP = octa-ethylporphinato) (2a,b), mononuclear Ti(IV) porphyrin peroxo complexes formed by reaction of TiP(O) with hydrogen peroxide; and FeP(O2)- (3a,b), mononuclear ferric porphyrin peroxo complexes formed by reaction of FeP with superoxide, O2-. In all three cases, sulfate was obtained as a product, in the form of sulfato complexes for 1 and 2 and in the form of free ionic sulfate for 3.
New Five- and Six-Coordinate Imidazole and Imidazolate Complexes of Ferric Tetraphenylporphyrine
Quinn, Robert,Nappa, Mario,Valentine, Joan S.
, p. 2588 - 2595 (2007/10/02)
The synthesis of several new imidazole and imidazolate complexes of ferric tetraphenylporphyrine (TPP) are reported.The following coplexes have been made with L = imidazole (ImH) or 4-methylimidazole (4MeImH) and L- = imidazolate (Im-) or 4-methylimidazolate (4MeIm-): FeTPP(L)(L-), -2>-, and (SbF6).Addition of Im- to FeTPPCl resulted in the formation first of the imidazolate-bridged complex + and then of -.Similar addition of 4MeIm- to FeTPPCl resulted in the formation first of the high-spin mononuclear complex FeTPP(4MeIm) and then of -.The affinity of (SbF6) for a second 4MeImH was found to be very high, with K >/= 107 M-1 in toluene, 25 deg C.By contrast, 4MeImH was found preferentially to hydrogen bond to Fe(TPP)(4MeIm), with K ca. 5 * 104 M-1 in THF, 25 deg C.Coordination of 4MeImH was only observed at high concentration of ligand (K ca. 50 +/- 10 M-1).The monoimidazole complex (SbF6) was concluded to be high spin after a comparison of the visible spectral properties of a large number of ferric TPP complexes.
