Proton nuclear magnetic resonance study of equilibriums and paramagnetisms of ferriprotoporphyrin IX-ligand complexations

Wang, Jin-Tsai; Yeh, Herman J. C.; Johnson, David

doi:10.1021/ja00476a023

Cited by 18 publications

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“…Spectrophotometric titrations of the reaction of [Mn(TPP)] with [K(222)(CN)] were performed in benzene at room temperature, and the spectroscopic results are shown in Figure . On the basis of the change values of absorbance, the K a of [K(222)][Mn II (TPP)(CN)] was estimated to be 3.72(±0.2) × 10 4 M –1 , which is comparable to 1.9(±0.3) × 10 4 M –1 of the cyano ferriprotoporphyrin IX …”

Section: Resultsmentioning

confidence: 99%

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Axial Mn–C_CN Bonds of Cyano Manganese(II) Porphyrin Complexes: Flexible and Weak?

Liu

2016

Inorg. Chem.

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Three five-coordinate high-spin (cyano)manganese(II) complexes, utilized tetraphenylporphyrin (TPP), tetratolylporphyrin (TTP), and tetramesitylporphyrin (TMP) as ligands, are prepared and studied by single-crystal X-ray, FT-IR, UV-vis, and EPR spectroscopies. The crystal structure studies revealed noteworthy structural features including unexpectedly wide tilting angles of the axial Mn-CCN bonds, which is contrasted to the isoelectronic Fe(III)-CCN bonds. Solid-state EPR measurements (90 K) and simulations are applied to obtain the ZFS parameters (D, E, and E/D (λ)), which are compared to Mn(II) porphyrin analogues of hemes to understand the ligand field of the cyanide. The solution EPR studies gave new insights into the chemical equilibrium of four- and five-coordinate species, which has been monitored by UV-vis spectroscopy.

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Section: Resultsmentioning

confidence: 99%

“…On the basis of the change values of absorbance, the K a of [K(222)][Mn II (TPP)(CN)] was estimated to be 3.72(±0.2) × 10 4 M −1 , which is comparable to 1.9(±0.3) × 10 4 M −1 of the cyano ferriprotoporphyrin IX. 25 The molecular structures of…”

Section: ■ Resultsmentioning

confidence: 99%

Axial Mn–C_CN Bonds of Cyano Manganese(II) Porphyrin Complexes: Flexible and Weak?

Liu

2016

Inorg. Chem.

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“…We have chosen the bis(cyanide) complexes by the following reasons. (1) Cyanide is a typical ligand to form a low spin ferric complex. , (2) Coordinated cyanide is considered to be a good proton acceptor in hydroxylic solvent such as methanol . Thus, it might be possible to obtain two sets of spectroscopic data by using two solvent systems, CD 2 Cl 2 and CD 2 Cl 2 −CD 3 OD, in which cyanide behaves as an axial ligand with different coordination strength.…”

Section: Introductionmentioning

confidence: 99%

Change in Electron Configuration of Ferric Ion in Bis(cyanide)(meso-tetraalkylporphyrinatoiron(III)), [Fe(TRP)(CN)₂]^-, Caused by the Nonplanarity of the Porphyrin Ring

et al. 1997

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The synthesis and characterization of a series of bis(cyanide)(meso-tetraalkylporphyrinatoiron(III)), [Fe(TRP)(CN) 2 ] -where R is H, Me, Et, and i Pr, are reported. The 1 H NMR spectrum of the unsubstituted [Fe(THP)(CN) 2 ] -shows a pyrrole signal at δ ) -23.19 ppm (-25 °C) in CD 2 Cl 2 , which is quite typical as a low spin ferric complex. As the bulkiness of the meso substituent increases, the pyrrole signal moves to lower magnetic field; 0.34, -2.26, and 11.94 ppm for [Fe(TMeP)(CN) 2 ] -, [Fe(TEtP)(CN) 2 ] -, and [Fe(T i PrP)(CN) 2 ] -, respectively. Corresponding to the pyrrole proton signal, the cyanide carbon signal also exhibits a large downfield shift. The difference in chemical shifts between [Fe(THP)(CN) 2 ] -and [Fe(T i PrP)(CN) 2 ] -reaches as much as 1443 ppm at -25 °C. The substituent dependent phenomena are also observed in EPR spectra taken in frozen CH 2 Cl 2 solution at 4.2 K. While the unsubstituted complex gives a so called large g max type signal at 3.65, the alkyl substituted complexes exhibit axial type spectra; the EPR parameters for [Fe(T i PrP)(CN) 2 ] -are g ⊥ ) 2.43 and g | ) 1.73. These results clearly indicate that the electronic ground state changes from the usual (d xy ) 2 (d xz , d yz ) 3 to the unusual (d xz , d yz ) 4 (d xy ) 1 as the substituent becomes bulkier. Analysis of the EPR g values reveals that the orbital of the unpaired electron has more than 90% d xy character in the alkyl substituted complexes. The unusual electron configuration is ascribed to the destabilization of d xy orbital and/or stabilization of d xz and d yz orbitals caused by the S 4 ruffled structure of the alkyl substituted porphyrin ring. Thus, in a strongly ruffled low spin complex such as [Fe(T i PrP)(L) 2 ] ( , electron configuration of iron is presented by (d xz , d yz ) 4 (d xy ) 1 regardless of the kind and basicity of the axial ligand (L). In fact, low spin bis(pyridine) complex [Fe(T i PrP)(Py) 2 ] + gives a pyrrole signal at quite a low field, δ ) +16.4 ppm at -87 °C, which is actually the lowest pyrrole signal ever reported for the low spin ferric porphyrin complexes. Correspondingly, the EPR spectrum taken at 77 K showed a clear axial type spectrum, g ⊥ ) 2.46 and g | ) 1.59. In every case examined, (d xz ,d yz ) 4 (d xy ) 1 ground state is more or less stabilized by the addition of methanol as exemplified by the further downfield shift of the pyrrole proton and cyanide carbon signals together with the smaller EPR g ⊥ values. The methanol effect is explained in terms of the stabilization of d xz and d yz relative to d xy due to the hydrogen bond formation between coordinated cyanide and methanol.

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“…It is well established that two CN – anions coordinate to porphinatoiron(III) in organic solvents. − Quite recently, a spectroscopic and kinetic study of the cyanide binding to a water-soluble ferric porphyrin (5,10,15,20-tetrakis(2,4,6-trimethyl-3-sulfonatophenyl)porphinatoiron(III)) revealed the formation of mono- and dicyano-adducts with K ass values of 5.5 × 10 5 and 3.8 × 10 5 M –1 , respectively, at pH 8.0 and 20 °C . Fe (III) TPPS (7 μM) also formed (CN – ) 2 Fe (III) TPPS in aqueous solution, with the K ass values for the 1:1 and 2:1 complex formation being 832 ± 97 and 2593 ± 474 M –1 , respectively, at pH 7.0 (0.1 M phosphate buffer) and 37 °C (Supporting Information, Figure S1).…”

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Supramolecular Ferric Porphyrins as Cyanide Receptors in Aqueous Solution

Watanabe

Kitagishi

Kawasaki

2011

ACS Med. Chem. Lett.

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All fundamental data about binding of the cyanide to a supramolecular complex composed of a per-O-methylated β-cyclodextrin dimer having an imidazole linker (Im3CD) and an anionic ferric porphyrin (Fe((III))TPPS) indicate that the Fe((III))TPPS/Im3CD complex is much better as an cyanide receptor in vivo than hydroxocobalamin, whose cyanide binding ability is lowered by its strong binding to serum proteins in the blood.

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Proton nuclear magnetic resonance study of equilibriums and paramagnetisms of ferriprotoporphyrin IX-ligand complexations

Cited by 18 publications

References 3 publications

Axial Mn–C_CN Bonds of Cyano Manganese(II) Porphyrin Complexes: Flexible and Weak?

Axial Mn–C_CN Bonds of Cyano Manganese(II) Porphyrin Complexes: Flexible and Weak?

Change in Electron Configuration of Ferric Ion in Bis(cyanide)(meso-tetraalkylporphyrinatoiron(III)), [Fe(TRP)(CN)₂]^-, Caused by the Nonplanarity of the Porphyrin Ring

Supramolecular Ferric Porphyrins as Cyanide Receptors in Aqueous Solution

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Proton nuclear magnetic resonance study of equilibriums and paramagnetisms of ferriprotoporphyrin IX-ligand complexations

Cited by 18 publications

References 3 publications

Axial Mn–CCN Bonds of Cyano Manganese(II) Porphyrin Complexes: Flexible and Weak?

Axial Mn–CCN Bonds of Cyano Manganese(II) Porphyrin Complexes: Flexible and Weak?

Change in Electron Configuration of Ferric Ion in Bis(cyanide)(meso-tetraalkylporphyrinatoiron(III)), [Fe(TRP)(CN)2]-, Caused by the Nonplanarity of the Porphyrin Ring

Supramolecular Ferric Porphyrins as Cyanide Receptors in Aqueous Solution

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Axial Mn–C_CN Bonds of Cyano Manganese(II) Porphyrin Complexes: Flexible and Weak?

Axial Mn–C_CN Bonds of Cyano Manganese(II) Porphyrin Complexes: Flexible and Weak?

Change in Electron Configuration of Ferric Ion in Bis(cyanide)(meso-tetraalkylporphyrinatoiron(III)), [Fe(TRP)(CN)₂]^-, Caused by the Nonplanarity of the Porphyrin Ring