Electronic structure of metalloporphyrins. 2. Experimental electron density distribution of (meso-tetraphenylporphinato)iron(III) methoxide

Abstract

The iron is displaced 0.48 A from the plane of the four nitrogens and 0.56 A from the mean porphyrin plane. The O-C bond of the methoxide is eclipsed with respect to one of the Fe-N bonds. The experimental electron distribution was determined by least-squares refinement including multipole deformation functions (R = 2.3%, Rw = 2.8%). Populations of the deformation functions in the carbon atoms of the porphyrin ligand agree well with those found previously in (mero-tetraphenylporphyrinato)cobalt(II), which suggests transferability of ligand density between complexes. An approximately spherical electron distribution is found at the iron site, and experimental d-orbital occupancies calculated for the iron atom from the deformation populations are consistent with a high-spin Fe(III) state. However, small but significant deviations from spherical symmetry are observed which, together with observed net atomic charges, have been used to calculate a Móssbauer quadrupole splitting constant of +0.6 (3) mm/s.

The crystal structure of halofantrine–ferriprotoporphyrin IX and the mechanism of action of arylmethanol antimalarials

“…Hf forms a 5-coordinate complex with Fe(III)PPIX via its hydroxyl group. The Fe-O bond length (1.840(4) Å) is consistent with an Fe(III)-alkoxide bond (1.816-1.851 Å) [31][32][33][34] rather than an Fe(III)-alcohol (2.113-2.160 Å) [38,39]. In addition, p-stacking of the phenanthrene ring over the porphyrin and intermolecular hydrogen bonding between the protonated N atom of Hf and the propionate of Fe(III)PPIX also occurs.…”

“…The Cambridge Structural Database (CSD) was surveyed for five-coordinate Fe(III) alkoxide complexes. Five molecules that are structurally similar to the Hf-Fe(III)PPIX structure were selected [31][32][33][34][35], as was the Hf-Fe(III)PPIX complex itself from the current work. For this type of study the force field is considered correct if the absolute difference between the crystal structure averages and the values returned by the force field agree within 0.01 Å for bond lengths, 2°for bond angles and 4°for torsion angles [29,30].…”

Structure of bis(pyridine)(5,10,15,20-tetraphenylporphyrinato)iron(II)–pyridine solvate, [Fe(C44H28N4)(C5H5N)2].2C5H5N

“…The relevance of porphyrin stereochemistry in biology is well documented (see, for example, Lever & Gray, 1983). The study of the title compound was undertaken as part of a program to map the electron density in iron porphyrins as a function of oxidation state, coordination number and spin state (Lecomte, Chadwick, Coppens & Stevens, 1983;Coppens & Li, 1984).…”

Molecular Stereochemistry of [FeIII(TPP)(OCOCF3)]

“…The structures of five mononuclear high-spin pentacoordinate oxygen-ligated iron complexes of the type [FelII(Por)(X)] (where Por = tetraphenylporphinato, TPP, or tetrakis(p-methoxyphenyl)porphinato, tp-MePP, and X = OCH3, OCOCH3, OSOC6H5, OSO3H or OSO2CH3) have been determined previously (Lecomte, Chadwick, Coppens & Stevens, 1983;Oumous, Lecomte, Protas, Cocolios & Guilard, 1984;Cocolios, Lagrange, Guilard, Oumous & Lecomte, 1984;Scheidt, Lee & Finnegan, 1988;Li et al, 1987). We report here the molecular stereochemistry of [FeIII(TpP)(OCOCF3)], (I), along with a structural comparison with related complexes.…”