High-Spin Iron(III) Tetramethylchiroporphyrins:  Structural, Magnetic, and ¹H NMR Studies

Abstract

The chloroiron(III) complex of R R -tetramethylchiroporphyrin, FeCl(TMCP), was prepared, and its structure was determined by X-ray crystallography. Black crystals of FeCl(TMCP)‚0.72CH 2 Cl 2 form in the tetragonal space group P4 3 2 1 2 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 1 H NMR spectra of the three species are consistent with their C 2 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 C 1 , R to the porphyrin meso position, appear at ca. 160-200 ppm, in keeping with the nearly perpendicular orientation of the C 1 -H bond with respect to the porphyrin mean plane. The temperature dependence of the 1 H NMR spectrum of FeCl(TMCP) suggests substantial zero-field splitting.

Density-Functional Theory Study of the Stereochemistry of Chloroiron(III) and Chloromanganese(III) Complexes of a Bridled Chiroporphyrin

“…This result is in agreement with the fact that, as effectively observed for :: 3, 16 the chloroiron(III) porphyrins are experimentally found to be HS species. 15,16 The ΔE LH values found for the RRRR-:: 3 in and RRRR-:: 3 out conformers are large (+2044 and +1408 cm -1 , respectively), and they are far greater than the value of +351 cm -1 obtained for the RβRβ-:: 3 atropisomer. This noticeable stabilization of the LS state with regard to the HS state upon the RRRR f RβRβ atropisomeriszation will be discussed below.…”

“…This result is consistent with the one obtained for 3ˆand with the fact that the chloroiron(III) porphyrins are HS species. 15,16 An inspection of Tables 4 and 7 shows that the value of ΔE LH is nearly the same in RRRR-3ˆo ut and RRRR-::…”

“…3) 16 and the chloromanganese(III) complex [MnCl(TMCP)] (4 . ), 47 which are similar to 3ˆand 4ˆbut are devoid of straps.…”

Antagonistic metal-directed inductions in catalytic asymmetric aziridination by manganese and iron tetramethylchiroporphyrins

“…11 The MnCl(TMCP) complex is structurally very similar to FeCl(TMCP). 12 Hence, intermolecular steric interactions during the approach of the olefin towards the nitrenoid species are presumably similar for the two metal catalysts, implying that electronic effects are responsible for the observed opposite enantioselectivities. We speculate that each metal center favors one of two competing mechanisms (Scheme 1).…”

Novel Copper(II) Induced Formation of a Porphyrinogen Derivative: X-ray Structural, Spectroscopic, and Electrochemical Studies of Porphyrinogen Complexes of Cu(II) and Co(III) Complex of a Trispyrazolyl Tripodal Ligand

“…The ligand (H 3 MPz 3 tren) shows different extents of deprotonation in these complexes. In the cobalt(III) compound [Co-(HMPz 3 tren)]ClO 4 (2), it loses two protons, while, in the corresponding Zn(II) complex [Zn(H 3 MPz 3 tren)](ClO 4 ) 2 (3), it remains completely neutral. The same reaction when carried out with Cu(II) ion followed an unprecedented path, leading to porphyrinogen complexes (1a, 1b) involving the (28) Barik The mean deviation of the basal plane N1A, N3, N1, and N3A is only 0.0151 Å (0.0156 Å for 1b).…”