155145-20-3Relevant academic research and scientific papers
Studies of iron(III) porphyrinates containing silanethiolate ligands
Meininger, Daniel J.,Caranto, Jonathan D.,Arman, Hadi D.,Tonzetich, Zachary J.
, p. 12468 - 12476 (2013)
The chemistry of several iron(III) porphyrinates containing silanethiolate ligands is described. The complexes are prepared by protonolysis reactions of silanethiols with the iron(III) precursors, [Fe(OMe)(TPP)] and [Fe(OH)(H 2O)(TMP)] (TPP = dianion of meso-tetraphenylporphine; TMP = dianion of meso-tetramesitylporphine). Each of the compounds has been fully characterized in solution and the solid state. The stability of the silanethiolate complexes versus other iron(III) porphyrinate complexes containing sulfur-based ligands allows for an examination of their reactivity with several biologically relevant small molecules including H2S, NO, and 1-methylimidazole. Electrochemically, the silanethiolate complexes display a quasi-reversible one-electron oxidation event at potentials higher than that observed for an analogous arenethiolate complex. The behavior of these complexes versus other sulfur-ligated iron(III) porphyrinates is discussed.
Effect of the axial ligand on the reactivity of the oxoiron(IV) porphyrin π-cation radical complex: Higher stabilization of the product state relative to the reactant state
Takahashi, Akihiro,Yamaki, Daisuke,Ikemura, Kenichiro,Kurahashi, Takuya,Ogura, Takashi,Hada, Masahiko,Fujii, Hiroshi
, p. 7296 - 7305 (2012/07/28)
The proximal heme axial ligand plays an important role in tuning the reactivity of oxoiron(IV) porphyrin π-cation radical species (compound I) in enzymatic and catalytic oxygenation reactions. To reveal the essence of the axial ligand effect on the reactivity, we investigated it from a thermodynamic viewpoint. Compound I model complexes, (TMP+a?€￠) FeIVO(L) (where TMP is 5,10,15,20-tetramesitylporphyrin and TMP +? is its π-cation radical), can be provided with altered reactivity by changing the identity of the axial ligand, but the reactivity is not correlated with spectroscopic data (ν(Fe=O), redox potential, and so on) of (TMP+?)FeIVO(L). Surprisingly, a clear correlation was found between the reactivity of (TMP+?)FeIVO(L) and the FeII/FeIII redox potential of (TMP)Fe IIIL, the final reaction product. This suggests that the thermodynamic stability of (TMP)FeIIIL is involved in the mechanism of the axial ligand effect. Axial ligand-exchange experiments and theoretical calculations demonstrate a linear free-energy relationship, in which the axial ligand modulates the reaction free energy by changing the thermodynamic stability of (TMP)FeIII(L) to a greater extent than (TMP +?)FeIVO(L). The linear free energy relationship could be found for a wide range of anionic axial ligands and for various types of reactions, such as epoxidation, demethylation, and hydrogen abstraction reactions. The essence of the axial ligand effect is neither the electron donor ability of the axial ligand nor the electron affinity of compound I, but the binding ability of the axial ligand (the stabilization by the axial ligand). An axial ligand that binds more strongly makes (TMP)FeIII(L) more stable and (TMP+?)FeIVO(L) more reactive. All results indicate that the axial ligand controls the reactivity of compound I (the stability of the transition state) by the stability of the ground state of the final reaction product and not by compound I itself.
One-electron oxidized product of difluoroiron(iii) porphyrin: Is it iron(iv) porphyrin or iron(iii) porphyrin π-cation radical?
Ikezaki, Akira,Takahashi, Masashi,Nakamura, Mikio
body text, p. 9163 - 9168 (2011/10/17)
The electronic structure of [Fe(TMP)F2], which is formally a one-electron oxidation equivalent above [FeIII(TMP)F 2]-, has been examined in solution by 1H NMR, UV-Vis, and Moessbauer spectroscopy. In CD2Cl2-CD 3OD solution at 193 K, the pyrrole-H and m-H signals appeared at 128.2 and 116.7 ppm, respectively. The UV-Vis spectrum showed broad absorption bands at 560-680 nm. The Moessbauer spectrum taken in frozen toluene-methanol solution exhibited a very broad single line from which the IS and QS values were determined by computer simulation to be 0.50 and 0.14 mm s-1, respectively. On the basis of these results, it was concluded that the one-electron oxidized product of [Fe(TMP)F2]- should be formulated as the iron(iii) radical cation [FeIII(TMP) F2], not as iron(iv) porphyrin [FeIV(TMP)F2] as previously suggested.
Identification of High-Valent Fluoroiron Porphyrin Intermediates Associated with the Electrocatalytic Functionalization of Hydrocarbons
Hickman, David L.,Nanthakumar, Alaganandan,Goff, Harold M.
, p. 6384 - 6390 (2007/10/02)
The difluoroiron(III) tetraphenylporphyrin complex undergoes a one-electron oxidation at 0.68 V (SCE) in contrast with values of 1.1 V measured for the monofluoroiron(III) porphyrin and the other five-coordinate iron(III) porphyrin complexes.Cyclic voltammetric oxidation of the difluoroiron(III) species in dichloromethane solution is quasi-reversible as a consequence of an EC mechanism.Reversible waves are favored at high scan rates and lower temperatures.Increased water content serves to make the oxidative cyclic voltammetric process irreversible presumably due to a disproportionation process.In the presence of added olefin substrates, this EC process permits efficient electrocatalytic oxidation to the epoxide, allylic alcohol, and enone.Tertiary carbon units are converted to the corresponding alcohol.Utilization of fluoride ion permits generation and low-temperature spectroscopic identification of a highly oxidized iron porphyrin species.The high-valent complex is produced at -78 deg C through addition of m-chloroperbenzoic acid to monofluoroiron(III) tetraarylporphyrins or by fluoride ion promoted disproportionation of the dication radical μ-oxo dimeric iron(III) porphyrin derivative.The oxidized iron porphyrin species is competent to effect olefin epoxidation at -78 deg C.Low-temperature 1H and 2H NMR spectroscopies demonstrate the porphyrin ?-cation radical nature of the high-valent species, in that porphyrin phenyl resonances are drastically shifted in alternating upfield and downfield directions.The electron spin resonance spectrum is consistent with an S = 3/2 ground state, and the high-valent intermediate is assigned a tentative fluorooxoiron(IV) porphyrin ?-cation radical formulation.
