52629-13-7Relevant academic research and scientific papers
Sharing the π-bonding. An iron porphyrin derivative with trans, π- accepting axial ligands. Synthesis, EPR and Mossbauer spectra, and molecular structure of two forms of the complex nitronitrosyl(α,α,α,α-tetrakis(o- pivalamidophenyl)porphinato)ferrate(II)
Nasri, Habib,Ellison, Mary K.,Chen, Shuxian,Huynh, Boi Hanh,Scheldt, W. Robert
, p. 6274 - 6283 (2007/10/03)
The reaction of the iron(II) picket fence porphyrin derivative [Fe(TpivPP)(NO2)]- (Nasri et al. J. Am. Chem. Soc. 1991, 113, 717) with NO has been examined. The result is a new hexacoordinated iron(II) porphyrin complex, [Fe(TpivPP)(NO2)(NO)]-. This compound has been characterized by UV-vis, IR, EPR, and Mossbauer spectroscopies. All data show that the species is low spin (S = 1/4 ). The EPR spectrum of [Fe(TpivPP)(NO2)(NO)]-(frozen chlorobenzene solution) is similar to that of five-coordinate nitrosyl derivatives of iron(II) porphyrinates with g(x) = 2.085, g(y) = 2.032, g(z) = 2.01, a(x) (14N) = 24 G, a(y) = 16.5 G, and a(z) = 16 G. Two crystalline forms of [Fe(TpivPP)(NO2)(NO)]- were obtained and their molecular structures determined. In both crystalline forms, the axial nitro ligand is inside the 'pocket' of the picket fence porphyrin derivative. In the first crystalline form isolated, there are two independent molecules, one of which has disorder in the nitro and nitrosyl groups while the other molecule has completely ordered axial ligands. In this first form, the plane of the nitro group is nearly perpendicular to the plane containing the nitrosyl group and the iron. In the second crystalline form, however, the two axial ligand planes are nearly parallel. Mossbauer investigations (solid state) show that the iron centers in the two different crystalline forms have different electronic properties. The Mossbauer parameters for the perpendicular form are δ = 0.22 mm/s and ΔE(q) = 1.78 mm/s (200 K) and for the parallel form δ = 0.35 mm/s and ΔE(q) = 1.2 mm/s (4.2 K). Mossbauer data are also presented for a related complex: five-coordinate [Fe(TPP)(NO)] (TPP = mesotetraphenylporphinato). IR spectra for the two forms also reveal distinctly different interactions of the trans (nitro) ligand.
Oxygenation Patterns for Substituted meso-Tetraphenylporphyrin Complexes of Iron(II). Spectroscopic Detection of Dioxygen Complexes in the Absence of Amines
Latos-Grazynski, Lechoslaw,Cheng, Ru-Jen,Mar, Gerd N. La,Balch, Alan L.
, p. 5992 - 6000 (2007/10/02)
The reaction of dioxygen with iron(II) porphyrins in inert solvents has been studied by 1H NMR spectroscopy in order to detect the presence of reactive intermediates.Sterically hindered porphyrins have been examined in which the formation of peroxo- and oxo-bridged dimeric structure is limited.The iron(II) porphyrins studied have 1H NMR spectra characteristic of intermediate-spin (S = 1), four-coordinate species.Reduction of iron(III) chloride (FeIIICl) or iron(III) chloride (FeIIICl) with either aqueous sodium dithionite or zinc amalgam in dichloromethane solution produces FeII or FeII.The previously reported reduction of these two porphyrins with piperidine has been reexamined and shown to form the bis(pipridine) adducts of the iron(II) porphyrins.Addition of dioxygen to paramagnetic iron(II) (FeII) in toluene solution below -70 deg C produces a new diamagnetic complex that is formulated as FeO2. 1H NMR spectroscopic observations indicated that, on warming, this species is successively converted to FeIIIO2FeIII and to FeIIIOFeIII.The latter has been previously isolated.Reaction of FeO2 with N-methylimidazole (N-MeIm) at -70 deg C results in the formation of (N-MeIm)FeO2.Addition of oxygen to FeII at -70 deg C in toluene solution results in the formation of diamagnetic FeO2.This, on warming, is converted to FeO2Fe and then to FeOH and FeOFe as the final stable products.Addition of dioxygen to FeII and FeII in dichloromethane solution at -70 deg C produces diamagnetic dioxygen adducts.On warming, these undergo dissociation to form the parent iron(II) complex and irreversible oxidation to form iron(III) porphyrin hydroxide and chloride.
