Wydział Chemii

M. Mazzanti

J. C. Marchon

Jacek Wojaczyński

Stanisław Wołowiec

Lechosław Latos-Grażyński

M. Shang

W. R. Scheidt

1998

Inorganic Chemistry

37

2476-2481

10.1021/ic9711933

Naukowa

Angielski

Artykuł

The chloroiron(III) complex of αβαβ-tetramethylchiroporphyrin, FeCl(TMCP), was prepared, and its structure was determined by X-ray crystallography. Black crystals of FeCl(TMCP)·0.72CH₂Cl₂ form in the tetragonal space group P4₃2₁2 with a = b = 13.245(1) Å and c = 26.355(5) Å at 130 K with Z = 4. The structure shows an unusual five-coordinate high-spin iron(III) center in a strongly ruffled and domed porphyrin, with short equatorial bond distances (Fe−N(av) = 2.034(9) Å), and the iron 0.64 Å out of the porphyrin mean plane toward the chlorine atom. The solid-state magnetic moment is 5.92 μ_B at 20 K, slightly decreasing to 5.68 μ_B at 300 K. In solution FeCl(TMCP) can be easily transformed to FeBr(TMCP) or FeOH(TMCP). The ¹H NMR spectra of the three species are consistent with their C₂ symmetry and S = ⁵/₂ spin state. The pyrrole proton resonances are shifted downfield to 80−100 ppm at 293 K, more than in the corresponding tetraaryl derivatives. The cyclopropyl protons on C₁, α to the porphyrin meso position, appear at ca. 160−200 ppm, in keeping with the nearly perpendicular orientation of the C₁−H bond with respect to the porphyrin mean plane. The temperature dependence of the ¹H NMR spectrum of FeCl(TMCP) suggests substantial zero-field splitting.

https://doi.org/10.1021/ic9711933

https://www.acs.org/content/acs/en.html