Proton magnetic resonance characterization of the intermediate (<i>S</i>=1) spin state of ferrous porphyrins

Mispelter, Joël; Momenteau, M.; Lhoste, Jean‐Marc

doi:10.1063/1.439266

Cited by 80 publications

(71 citation statements)

References 23 publications

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“…Calculations on FeP by Kozlowski et al 31. using the BP and B3LYP functionals predicted the ground state to be 3 A 2g , in agreement with the experiments on FeTPP (iron tetraphenylporphine) 8-12. However, it is known that the ability of DFT to calculate the relative spin-state energies is sensitive to the type of functionals;31 the mentioned BP functional in fact fails to give the correct ground state for high-spin systems,32 although it provides a “correct” intermediate-spin ground state for FeP.…”

Section: Introductionsupporting

confidence: 65%

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Iron Porphyrins with Different Imidazole Ligands. A Theoretical Comparative Study

2010

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A theoretical comparative study of a series of five-and six-coordinate iron porphyrins, FeP(L) and FeP(L)(O 2 ), has been carried out using DFT methods, where P = porphine and L = imidazole (Im), 1-methylimidazole (1-MeIm), 2-methylimidazole (2-MeIm), 1,2-dimethylimidazole (1,2-Me 2 Im), 4-ethylimidazole (4-EtIm), or histidine (His). Two ligated "picket fence" iron porphyrins, FeTpivPP(2-MeIm) and FeTpivPP(2-MeIm)(O 2 ), were also included in the study for comparison. A number of density functionals were employed in the computations in order to obtain reliable results. The performance of functionals and basis set effects were investigated in detail on FeP, FeP(Im), and FeP(Im)(O 2 ), for which certain experimental information is available and there are some previous calculations in the literature for comparison. Many subtle distinctions in the effects of the different imidazole ligands on the structures and energetics of the deoxy-and oxy iron porphyrins are revealed. While FeP(2-MeIm) is identified to be high spin (S = 2), the ground state of FeP(1-MeIm) may be an admixture of a high-spin (S = 2) and an intermediate-spin (S = 1) state. The ground state of FeP(L)(O 2 ) may be different with different L. A weaker Fe-L bond more likely leads to an open-shell singlet ground state for the oxy complex. The 2-methyl group in 2-MeIm, which increases steric contact between the ligand and the porphyrinato skeleton, weakens the Fe-O 2 bond, and thus iron porphyrins with 2-MeIm mimic T-state (low affinity) hemoglobin. The calculated FeP(2-MeIm)-O 2 bonding energy is comparable to the FeTpivPP(2-MeIm)-O 2 one, in agreement with the fact that the "picket-fence" iron porphyrin binds O 2 with affinity similar to that of myoglobin, but different from the result obtained by the CPMD scheme. Im and 4-EtIm closely resemble His, the biologically axial base, and so future computations on hemoprotein models can be simplified safely by using Im.

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Section: Introductionsupporting

confidence: 65%

“…ferrous) porphyrins without axial ligands. It is now generally accepted that the ground state is intermediate spin (S = 1): only the 3 A 2g state arising from the (d z 2) 2 (d xy ) 2 (d π ) 2 configuration is compatible with Mössbauer,8,9 magnetic moment,10 and proton NMR11,12 data.…”

Section: Introductionmentioning

confidence: 99%

Iron Porphyrins with Different Imidazole Ligands. A Theoretical Comparative Study

2010

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“…Thus FeT(o/p-R)PP with M= 1, 3, 5 and FeT(o/p-R)PPCl with M=2, 4, 6 were examined and the spin state with the lowest energy was obtained. The spin state with the lowest energy is the triplet for FeT(o/p-R)PP, whereas the sextet for FeT(o/p-R) PPCl theoretical studies [19,[31][32][33][34][35][36][37][38][39]. For FeT(o/p-R)PPCl, Scheidt and Reed [40] have pointed out that the coordination of strong or moderate field ligands usually results in low-spin state, while the coordination of weak field ligands is inclined to cause high-spin state.…”

Section: Methodsmentioning

confidence: 96%

Substituent effects on geometric and electronic properties of iron tetraphenylporphyrin: a DFT investigation

She

et al. 2011

J Mol Model

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To investigate the effects of the substituents, substituent positions and axial chloride ligand on the geometric and electronic properties of the iron tetraphenylporphyrin (FeTPP), a series of the substituented iron tetraphenylporphyrins and their chlorides, FeT(o/p-R)PP and FeT(o/p-R)PPCl (R = -H, -Cl, -NO(2), -OH, -OCH(3)), were systematically calculated without any symmetry constraint by using DFT method. For geometric structure, the substituent position and axial Cl ligand change the configuration of the iron porphyrin obviously. The ortho-substituents prefer making the phenyls perpendicular to the porphyrin ring; the axial chloride draws the central Fe ion ~0.500 Å out of the porphyrin plane toward the ligand. With regard to electronic properties, it is found that E(LUMO) could be related to the catalytic activity. The electron-withdrawing group always lowers the energies of both frontier orbitals, while the electron-donating one heightens them simultaneously, but they affect the E(HOMO) and E(LUMO) in the same sequence, -NO(2) < -Cl < -H < -OH < -OCH(3). The substituent effects on the central Fe ion were explored by calculating NBO charge distribution, spin density and natural electron configuration.

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“…Reduction with Na,S,O, in toluene/H,O afforded quantitatively the doubly-bridged Fe(I1)-porphyrin 18 displaying typical absorption maxima at 541, 445, and 418 nm. In the 'H-NMR spectrum of 18, the protons of the bridging CH, groups appear within an extremely wide range from 24 to -57 ppm, due to the paramagnetism of the complex and accounting for a four-coordinate Fe(I1) with intermediate spin state (S = 1) [29]. The same product was obtained by the so called 'direct-insertion' (FeBrJutidine, THF/benzene) according to Collman and Groh [21], omitting the formation of 17.…”

Section: Scliemcmentioning

confidence: 99%

Synthetic Models of the Active Site of Cytochrome P‐450. 1st Communication. The Synthesis of a Doubly‐Bridged Iron(II)‐Porphyrin Carrying a Tightly Bound Thiolate Ligand

Stäubli

Fretz

Piantini

et al. 1987

Helvetica Chimica Acta

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The doubly-bridged iron(I1)-tetraphenylporphyrin derivative 6, carrying a sterically fixed S-ligand in the 'proximal'position and the substrate at the 'distal' site, was synthesised as an enzyme model for cytochrome P-450. Compound 36, the CO complex of 6, displays a split Sorer band (403 and 457 nm) similar to the native cytochrome P-450.Introduction. -The significance of cytochrome-P-450-catalysed oxygenations in the metabolism of endogenous compounds and xenobiotics [ 11 [2] has stimulated intensive research focussing on 1 ) the investigation of the reaction mechanisms of P-450 monooxygenases from bacterial [3], plant [4], and mammalian [5] [6] sources, and 2) the synthesis and application of iron-tetraphenylporphyrin derivatives, structurally related to the active site of these enzymes [7-91. The results of these investigations led to the formulation

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Proton magnetic resonance characterization of the intermediate (S=1) spin state of ferrous porphyrins

Cited by 80 publications

References 23 publications

Iron Porphyrins with Different Imidazole Ligands. A Theoretical Comparative Study

Iron Porphyrins with Different Imidazole Ligands. A Theoretical Comparative Study

Substituent effects on geometric and electronic properties of iron tetraphenylporphyrin: a DFT investigation

Synthetic Models of the Active Site of Cytochrome P‐450. 1st Communication. The Synthesis of a Doubly‐Bridged Iron(II)‐Porphyrin Carrying a Tightly Bound Thiolate Ligand

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