61085-06-1Relevant academic research and scientific papers
?-BONDED METHYLIRON PORPHYRINS? THE CONVERSION OF IRON(III) TO MAGNESIUM(II) PORPHYRINS BY METHYL-GRINGNARDS
Castro, C. E.,Kishore, D.
, p. C27 - C30 (1985)
Iron(III) porphyrins react with methyl-Gringnard reagents to produce in sequence two similar but distinct S = 1 iron(II) porphyrins followed by the magnesium(II) complex.Stable porphyrin alkylirons are not produced by the methyl-Gringnards, methyllithium,
Electrochemistry and spectroelectrochemistry of iron porphyrins in the presence of nitrite
Wei, Zhongcheng,Ryan, Michael D.
, p. 49 - 57 (2008/10/08)
The reaction of nitrite with ferric and ferrous porphyrins was examined using visible, infrared and NMR spectroscopy. Solutions of either ferric or ferrous porphyrin were stable in the presence of nitrite, with only complexation reactions being observed. Under voltammetric conditions, though, a rapid reaction between nitrite and iron porphyrins was observed to form the nitrosyl complex, Fe(P)(NO), where P=porphyrin. The products of the reduction of ferric porphyrins in the presence of nitrite were confirmed by visible spectroelectrochemistry to be Fe(P)(NO) and [Fe(P)]2O. Visible, NMR and infrared spectroscopy were used to rule out the formation of Fe(P)(NO) by the iron-catalyzed disproportionation of nitrite. A reaction between iron porphyrins and nitrite only occurred by the presence of both oxidation states (ferric/ferrous). The kinetics of the reaction were monitored by visible spectroscopy, and the reaction was found to be first-order with respect to Fe(OEP)(Cl) and Fe(OEP). The products were the same as those observed in the spectroelectrochemical experiment. The rate was not strongly dependent upon the concentration of nitrite, indicating that the coordinated, not the free nitrite, was the reaction species. The kinetics observed were consistent with a mixed oxidation state nitrite-bridged intermediate, which carried out the oxygen transfer reaction from nitrite to the iron porphyrin. The effect of nitrite coordination on the reaction rate was examined.
Kinetics, mechanism and thermodynamics of iron carbon bond dissociation in organoiron porphyrin complexes
Riordan, Charles G.,Halpern, Jack
, p. 19 - 24 (2008/10/08)
Thermolysis of Fe(P)R (P = octaethylporphyrinato dianion, R = C6H5, CH3, C2H5, CH2C(CH3)3; P = tetraphenylporphyrinato dianion, R = C6H5; P = tet
Synthesis and electron delocalization of [Fe4S4]-S-Fe(III) bridged assemblies related to the exchange-coupled catalytic site of sulfite reductases
Cai, Lisheng,Holm
, p. 7177 - 7188 (2007/10/02)
Because of the pervasive occurrence of magnetically coupled siroheme and Fe4S4 units in assimilatory and dissimilatory sulfite and nitrite reductases, we have undertaken the synthesis of the sulfide-bridged assembly Fe4S4-S-heme as a possible analogue to the active sites of certain assimilatory enzymes. The approach has utilized iron subsite-differentiated clusters of the type [Fe4S4(LS3)L′]2-, which undergo regiospecific substitution at the unique subsite. Reaction of [Fe4S4(LS3)(SEt)]2- with limited H2S in acetonitrile affords the functionalized cluster [Fe4S4(LS3)(SH)]2- (4), which exists in equilibrium with the μ-S double cubane {[Fe4S4(LS3)]2S}4- (6) and H2S. Reaction of 4 and [Fe(salen)]2O gave the bridged assembly [Fe4S4(LS3)-S-FeIII(salen)] 2- (8), detectable by its characteristic isotropically shifted 1H NMR spectrum. Six routes were devised to a related heme-based assembly: directed acid-base coupling of 4 with [Fe(OEP)]2O, [Fe(OEP)(OMe)], [Fe(OEP)(OC(Me)=CH2)], and [Fe(OEP)-(OClO3)]/Et3N; Si-S bond cleavage in the reaction of [Fe4S4(LS3)(SSiEt3)]2- with [Fe(OEP)F]; oxidative addition of [FeII(OEP)] to the disulfide bond of the μ-S2 double cubane {[Fe4S4(LS3)]2S2} 4- (7). In each case, the product was [Fe4S4(LS3)-S-FeIII(OEP)] 2- (9), recognizable by UV-visible absorption and 1H NMR spectra. Both 8 and 9 contain [Fe4S4]2+ and high-spin Fe(III) fragments. Isotropic shifts mainly contact in origin that are enhanced by factors of 7-12 compared to those of precursor cluster 4, and the Curie-type temperature dependence of the shifts of 9, originate from extensive spin localization from the Fe(III) fragment to the cluster. This effect requires the existence of a covalent bridge between the fragments and, together with the methods of synthesis and other spectroscopic observations, provides structure proof of the bridged assemblies. These species sustain two one-electron reduction reactions; other reactions of 9, which alter or cleave the bridge, are summarized. The electronic features of bridged assemblies such as 8 and 9 approach the intrinsic magnetic and spectroscopic properties of a structurally similar unit in the oxidized enzymes and potentially provide a means of identification of such units. (LS3 = 1,3,5-tris[(4,6-dimethyl-3-mercaptophenyl)-thio]-2,4,6-tris(p-tolylthio) benzene(3-); OEP = octaethylporphyrinate(2-); salen = 1,2-bis(salicylideneamino)ethane-(2-).).
(1)H NMR spectra and electronic structure of reduced iron porphyrins: Fe(II), Fe(I) and Fe(0) porphyrins
Sinyakov, G.N.,Shulga, A.M.
, p. 1 - 14 (2007/10/02)
Fe(II), Fe(I) and Fe(0) porphyrins have been generated by stepwise reduction with a sodium mirror in vacuum and their (1)H NMR spectra have been recorded and analyzed.Fe(II) porphyrins (Fe(II)P) have been examined in three spin states, an S = 0 state in pyridine-d8, an S = 1 state in benzene-d6 and an S = 2 state in tetrahydrofuran-d8 (THF-d8).The analysis of isotropic shifts for low-spin Fe(II)P (S = 0) has indicated that no charge transfer has been observed.The ground state configuration is (dxy)2(dxz,dyx)4.The contact shifts for intermediate-spin Fe(II)P (S = 1) reflect P -> Fe ? charge transfer.The proposed electron configuration is (dxy)2 (dz2)2 (dxz,dyz)2, which agrees with Moessbauer data.The pattern of contact shifts for high-spin Fe(II)P (S = 2) is consistent with ? spin transfer, which suggests that the d(x2-y2) orbital possesses an unpaired spin.The electron configuration is (dxy)2 (dxz,dyz)2 (dz2)1 (d(x2-y2))1.Our results for Fe(II)P (S = 1,2) agree with the literature (1)H NMR data.In the case of Fe(I)P in THF, the separation of isotropic shifts into the dipolar and contact contributions has shown the dominance of the latter.The observed shifts indicate negative ? spin density on pyrrole and meso carbon atoms of the ligand, which seems to be due to a strong ?-? spin polarization effect.When this fact is taken into account the pattern of contact shifts is consistent with ? spin transmission involving both P -> Fe ? charge transfer out of the ligand-filled molecular (3e(?)) orbital and Fe -> P ?* charge transfer into the ligand highest unoccupied (4e(?*)) molecular orbital.The occurrence of the unpaired spin in this molecular orbital is consistent with ?-radical anion formulation which was found by X-ray crystallography.An S = 1/2 spin state determined by magnetic moment measurements agrees with the most probable electron configuration (dxy)2 (dxz,dyz)3 (dz2)2.In the case of Fe(0)P, the isotropic shifts were found to be small, providing evidence of some spin transfer.The ground state configuration is (dxy)2 (dxz,dyz)4 (dz2)2.
