Control of spin state in (porphinato)iron(III) complexes. An axial ligand orientation effect leading to an intermediate-spin complex. Molecular structure and physical characterization of the monoclinic form of bis(3-chloropyridine)(octaethylporphinato)iron(III) perchlorate

Scheidt, W. Robert; Geiger, David K.; Hayes, Robert G.; Lang, Georgina

doi:10.1021/ja00347a018

Cited by 67 publications

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“…4 In the second polymorph, the projection of the two planar axial ligands nearly eclipses an Fe-N p bond direction and an intermediate-spin state was found. 5 The differences in physical properties were clearly related to absolute orientation of the axial ligands and these results led to further study of the effects of axial ligand orientation on the electronic structure of iron porphyrinates.…”

Section: Introductionmentioning

confidence: 98%

“…Systems for which this is shown include cytochromes b 5 Although some effort was required to obtain iron(III) species with perpendicular ligand orientations, we had assumed that for the closed subshell configuration of low-spin d 6 Fe(II) porphyrinates two planar axial ligands would prefer to align themselves in mutually perpendicular planes in order to maximize the π-bonding interactions between the filled dπ orbitals of Fe(II) and the π* orbitals of the ligands. However, subsequent studies 26 showed that obtaining iron(II) derivatives with mutually perpendicular orientations was not as readily achieved as in the iron(III) species.…”

Section: Introductionmentioning

confidence: 99%

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Relative Axial Ligand Orientation in Bis(imidazole)iron(II) Porphyrinates: Are “Picket Fence” Derivatives Different?

Nair

Noll

et al. 2008

Inorg. Chem.

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The synthesis of three new bis(imidazole)-ligated iron(II) picket fence porphyrin derivatives, [Fe (TpivPP)(1-RIm) 2 ] 1-RIm = 1-methyl-, 1-ethyl-, or 1-vinylimidazole) are reported. X-ray structure determinations reveal that the steric requirements of the four α,α,α,α-o-pivalamidophenyl groups lead to very restricted rotation of the imidazole ligand on the picket side of the porphyrin plane; the crowding leads to an imidazole plane orientation eclipsing an iron-porphyrin nitrogen bond. An unusual feature for these diamagnetic iron(II) species is that all three derivatives have the two axial ligands with a relative perpendicular orientation; the dihedral angles between the two imidazole planes are 77.2°, 62.4°, and 78.5°. All three derivatives have nearly planar porphyrin cores. Mössbauer spectroscopic characterization shows that all three derivatives have quadrupole splitting constants around 1.00 mm/s at 100K.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Relative Axial Ligand Orientation in Bis(imidazole)iron(II) Porphyrinates: Are “Picket Fence” Derivatives Different?

Nair

Noll

et al. 2008

Inorg. Chem.

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“…Both crystalline forms had identical composition but, as we discovered, substantially different solid-state temperature-dependent magnetic susceptibilities. The second phase is not a spin-crossover system, but instead represents the third possible spin state for iron(III), namely a quantum-admixed intermediate spin state [49]. We have found many more examples of Nligated intermediate-spin systems subsequently [50][51][52].…”

Section: Discussionmentioning

confidence: 97%

Explorations in metalloporphyrin stereochemistry, physical properties and beyond

Scheidt

2008

J. Porphyrins Phthalocyanines

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A review of selected portions of our work in the area of porphyrin structure and physical characterization is presented. Topics covered include early work on periodic trends in first row transtion metalloporphyrins, a survey of electronic structure of iron derivatives including spin-state trends, ligand orientation effects and the elucidtion of unusual low-spin states for iron(II). A discussion of the different tlypes of high-spin iron(II) complexes and the effects of hydrogen bonding is given. A survey of nitric oxide (NO) derivatives is presented as well as a brief introduction into the use of nuclear resonance vibrational spectroscopy for the study of iron porphyrins and heme proteins.

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“…Changes in the absolute orientation of the two ligands can lead to the differing spin states of the iron with high-spin, intermediate-spin and low-spin species resulting that are clearly related to the absolute ligand orientations [2, 3]. In addition for low-spin species, the relative orientation of the two axial ligands has substantial effects on the energies of the three lowest energy d orbitals [4, 5, 6, 7, 8, 9, 10, 11].…”

Section: Introductionmentioning

confidence: 99%

Characterization of the mixed axial ligand complex (4-cyanopyridine)(imidazole)(tetramesitylporphinato)iron(iii) perchlorate. Stabilization by synergic bonding

Serth-Guzzo

Turowska‐Tyrk

Walker

et al. 2016

J. Porphyrins Phthalocyanines

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The reaction of [Fe(TMP)(OClO3)], where TMP is the dianion of tetramesitylporphyrin, with a combination of a strong π-acceptor ligand and a π-donating imidazole can lead to the preparation of mixed-ligand complexes [Fe(Porph)(4-CNPy)(L)]+ where L is imidazole itself or 1-acetylimidazole and 4-cyanopyridine is the strong π acceptor ligand. The stability of the new mixed-ligand pair is the presumed result of synergic bonding between the two axial ligands. The molecular structure and other characterization of the new mixed axial ligand complex, [Fe(TMP)(4-CNPy)(HIm)]ClO4 is described. The axial ligands have a relative perpendicular arrangement with Fe–N(imidazole) = 1.945 Å and Fe–N(pyridine) = 2.021 Å The average equatorial Fe–Np distance is 1.963 Å, which is consistent with the S4-ruffled TMP core. Despite the relative perpendicular arrangement of axial ligands, the EPR spectrum of the complex is a rhombic signal and not a large gmax signal. The EPR g-values are g1 = 3.05, g2 = 2.07, and g3 = 1.22. A quadrupole doublet was seen in the Mössbauer spectrum with an isomer shift of 0.197 mm/s and quadrupole splitting of 1.935 mm/s. Two crystalline forms of [Fe(TMP)(4-CNPy)(HIm)]ClO4 have been characterized; the two forms differ only in the solvent content of the lattice. Crystal data for form A: a = 15.432 (12) Å, b = 20.696 (2) Å, c = 19.970 (5) Å, and β = 99.256 (14)°, monoclinic, space group P21/n, V = 6295 (2) Å3, Z = 4, formula FeCl3O4N8C69H69, 8397 observed data, R1 = 0.086, wR2 = 0.210, refinement on F 2. Crystal data for form B: a = 15.267 (3) Å, b = 20.377 (6) Å, c = 19.670 (4) Å, and β = 98.14 (1)°, monoclinic, space group P21/n, V = 6058 (4) Å3, Z = 4, formula C65.25H60.5Cl1.5FeN8O4, 5464 observed data, R1 = 0.096, wR2 = 0.112, refinement on F.

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Control of spin state in (porphinato)iron(III) complexes. An axial ligand orientation effect leading to an intermediate-spin complex. Molecular structure and physical characterization of the monoclinic form of bis(3-chloropyridine)(octaethylporphinato)iron(III) perchlorate

Cited by 67 publications

References 0 publications

Relative Axial Ligand Orientation in Bis(imidazole)iron(II) Porphyrinates: Are “Picket Fence” Derivatives Different?

Relative Axial Ligand Orientation in Bis(imidazole)iron(II) Porphyrinates: Are “Picket Fence” Derivatives Different?

Explorations in metalloporphyrin stereochemistry, physical properties and beyond

Characterization of the mixed axial ligand complex (4-cyanopyridine)(imidazole)(tetramesitylporphinato)iron(iii) perchlorate. Stabilization by synergic bonding

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