52676-83-2Relevant academic research and scientific papers
Structures and properties of octaethylporphinato(phenolate)iron(III) complexes with NH?O hydrogen bonds: Modulation of Fe-O bond character by the hydrogen bond
Kanamori, Daisuke,Yamada, Yusuke,Onoda, Akira,Okamura, Taka-Aki,Adachi, Seiji,Yamamoto, Hitoshi,Ueyama, Norikazu
, p. 331 - 338 (2008/10/09)
Iron(III) porphinate complexes of phenolate that have NH?O hydrogen bonds on the coordinating oxygen were synthesized as models of heme catalase. The NH?O hydrogen bonds in the complexes lower an electron donation from the coordinating oxygen to iron and induce a long Fe-O bond and a positive redox potential. Iron(III) porphinate complexes of phenolate that have NH?O hydrogen bonds on the coordinating oxygen, [FeIII(OEP){O-2,6-(RCONH) 2C6H3}] (R = CF3 (1), CH3 (3)) and [FeIII(OEP)(O-2-RCONHC6H4)] (R = CF3 (2), CH3 (4)) (OEP = 2,3,7,8,12,13,17,18-octaethyl- 21H, 23H-porphinato), were synthesized and characterized as models of heme catalase. The presence of NH?O hydrogen bonds was established by their crystal structures and IR shifts of the amide NH band. The crystal structure of 1 shows an extremely elongated Fe-O bond, 1.926(3) ?, compared to 1.887(2) ? in 2 or 1.848(4) ? in [FeIII(OEP)(OPh)]. The NH?O hydrogen bond decreases an electron donation from oxygen to iron, resulting in a long Fe-O bond and a positive redox potential.
Spectrophotometric and resonance Raman studies on the formation of phenolate and thiolate complexes of (octaethylporphinato)iron(III)
Uno, Tadayuki,Hatano, Keiichiro,Nishimura, Yoshifumi,Arata, Yoji
, p. 2803 - 2807 (2008/10/08)
Reactions of (octaethylporphinato)iron(III) methoxide, Fe(OEP)(OMe), with a series of phenols, carboxylic acids (ROH), and thiols (RSH) were monitored by spectrophotometric techniques. The equilibrium constants for addition of ROH to Fe(OEP)(OMe) were measured, and it was found that increased acidity of the ROH moiety caused the equilibrium constant to increase. The reaction of Fe(OEP)(OMe) with RSH proceeded significantly slowly at 20°C. The second-order rate constants were obtained and were found to increase with the increase of RSH acidity. These indicate that dissociation of a proton from an ROH or RSH moiety will promote the formation of the product species Fe(OEP)(OR) or Fe(OEP)(SR). By the use of resonance Raman spectroscopy, both product species were found to be five-coordinate ferric high-spin complexes. The Fe(OEP)(OPh) complex showed the ν(Fe-OPh) stretching Raman line at 607 cm-1. The visible absorption maxima of the porphyrin π to iron dπ transitions (CT band) of Fe(OEP)(OR) and Fe(OEP)(SR) were a linear function of the pKa of ROH and RSH, and the hypsochromic shift with the increasing pKa was explained in terms of the electron-donating ability of the OR and SR ligands. The absorption maxima of Fe(OEP)(SR) were generally shifted to longer wavelength than those of Fe(OEP)(OR).
Reactions of aryl-iron(III) porphyrins with dioxygen. Formation of aryloxy-iron(III) and aryl-iron(IV) complexes
Arasasingham, Ramesh D.,Balch, Alan L.,Hart, Rebecca L.,Latos-Grazyński, Lechos?aw
, p. 7566 - 7571 (2007/10/02)
The reaction of dioxygen with low-spin, five-coordinate complexes, PFeIIIAr (P, porphyrin dianion; Ar, aryl group) has been examined for comparison with previous work (Arasasingham, R. D. et al. J. Am. Chem. Soc. 1989, 111, 4357) on the corresponding alkyl complexes which showed that peroxo complexes PFeIIIOOR formed initially and then decomposed to form PFeOH and an aldehyde or ketone when R was a primary or secondary alkyl group. Dioxygen addition to TTPFeIII(C6H4CH3-ρ) at 25 °C in toluene yields the phenoxide complex, TTPFe(OC6H4CH3-ρ), as the principle product, while addition to TTPFeIIIC6H5 at -30 °C yields TTPFeIIIOC6H5 and small amounts of TTPFeIII(OC6H4OH-ρ) and TTPFeIIIOC6H4OFeIIITTP. These reactions have been monitored by both 1H NMR and ESR spectroscopies. No intermediates have been detected in the formation of these products. Mechanisms for the formation of these products have been formulated in terms of the initial insertion of dioxygen into the Fe-C bond followed by rapid homolysis to form PFeIV=O and .OAr, with subsequent reactions yielding the final products. Addition of dioxygen to a solution of TTPFeIII(C6H4CH3-ρ) in chloroform at -60 °C yields a mixture of [TTPFeIV(C6H4CH3-ρ)]+ and TTPFeIIICl with no evidence for the formation of the phenoxide complexes. In this case electron transfer to yield the oxidized iron porphyrin and Superoxide ion is driven by the solvent polarity and the ability of the solvent to destroy Superoxide ion as it is formed.
