Synthesis and characterization of a manganese(III) porphyrin cation radical and its conversion to manganese(IV) by ligand metathesis

Spreer, Larry O.; Maliyackel, A. C.; Holbrook, Stephen R.; Otvos, John W.; Calvin, Melvin

doi:10.1021/ja00268a037

Cited by 29 publications

(15 citation statements)

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“…Our results for TPPMnCl appear to contradict those of Spreer et al (3). These workers reported that a band at 1280cm-' observed for the crystalline cation radical TPPMnC1SbCl6.4C2H2Cl4 was lost on prolonged exposure to vacuum, and suggested that the 1280cm-' band was due to the tetrachloroethane solvate molecules, rather than the cation radical.…”

Section: Resultscontrasting

confidence: 99%

In-situ Fourier transform infrared spectroelectrochemical studies of the oxidation of some tetraphenylporphyrin complexes

Hinman¹,

Pavelich²,

McGarty³

1988

Can. J. Chem.

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In-situ FTIR spectroelectrochemistry has been applied to determine difference spectra in the region 1800 to 1000 cm−1 associated with the oxidation of TPPH2, TPPMg, TPPCu, TPPZn, TPPCo, TPPMnCl, and TPPFeCl. In all cases, formation of the π-cation radical results in two characteristic absorbance decreases near 1600 and 1485 cm−1, and five characteristic absorbance increases near 1415, 1350, 1285, 1225, and 1005 cm−1. Formation of the π-dication was observed for TPPZn, TPPMg, and TPPCo, and gave rise to a new absorbance increase near 1600 cm−1, and a shift to higher frequency of bands in the 1200 to 1400 cm−1 region. Perchlorate coordination to oxidized TPPZn, TPPMg, and TPPCo gives rise to bands near 1140 and 1030 cm−1.

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Section: Resultscontrasting

confidence: 99%

In-situ Fourier transform infrared spectroelectrochemical studies of the oxidation of some tetraphenylporphyrin complexes

Hinman¹,

Pavelich²,

McGarty³

1988

Can. J. Chem.

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“…Coordination of acetylene to Co, however, would not change the Co II porphyrin π-cation radical structure, probably because the energy level of the singly occupied d z 2 orbital is not raised, owing to the π-acceptor character of acetylene. Magnetic properties of various metalloporphyrin π-cation radicals have been interpreted in terms of the occupancy and symmetry of the orbitals on the metal and on the ligand that contain an unpaired electron …”

Section: Resultsmentioning

confidence: 99%

Reversible Complexation of Acetylene with (Perchlorato)cobalt(III) Porphyrins To Form a Novel Dicobalt(II) Bis(porphyrin) with a Vinylene-N,N‘ Linkage

et al. 1997

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Perchlorato)cobalt(III) porphyrins bind acetylene reversibly in anhydrous CH 2 Cl 2 . The 1 H NMR and UV-vis spectra of the acetylene adduct at room temperature are characteristic of a Co II N-substituted porphyrin. The ESR spectra of the acetylene adduct in CH 2 Cl 2 at 4.2 and 77 K showed signals due to a π-cation radical and low-spin Co II . These spectroscopic data show that one acetylene combines with two cobalt porphyrins to generate a vinylene-N,N′-linked bis(porphyrin) dicobalt(II) structure reversibly via an acetylene π-complex of Co II porphyrin π-cation radical. When coordinating anionic axial ligands (Cl -, SCN -) were attached, the vinylene-N,N′ bis(tetraarylporphyrin) dicobalt(II) complexes were stabilized enough to be isolated and fully characterized.

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“…Axial ligand-dependent valence tautomerism has also been observed in Mn porphyrins, where the addition of strong axial donors such as CH 3 O − to Mn III (TPP •+ )(Cl) induces the formation of Mn IV (TPP)(OCH 3 ) 2 . 19 …”

Section: Introductionmentioning

confidence: 99%

Strong Inhibition of O-Atom Transfer Reactivity for Mn^IV(O)(π-Radical-Cation)(Lewis Acid) versus Mn^V(O) Porphyrinoid Complexes

et al. 2015

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The oxygen atom transfer (OAT) reactivity of two valence tautomers of a MnV(O) porphyrinoid complex was compared. The OAT kinetics of MnV(O)(TBP8Cz) (TBP8Cz = octakis(p-tert-butylphenyl)corrolazinato3−) reacting with a series of triarylphosphine (PAr3) substrates were monitored by stopped-flow UV-vis spectroscopy, and revealed second-order rate constants ranging from 16(1) to 1.43(6) × 104 M−1 s−1. Characterization of the OAT transition state analogs MnIII(OPPh3)(TBP8Cz) and MnIII(OP(o-tolyl)3)(TBP8Cz) was carried out by single-crystal X-ray diffraction (XRD). A valence tautomer of the closed-shell MnV(O)(TBP8Cz) can be stabilized by the addition of Lewis and Brønsted acids, resulting in the open-shell MnIV(O)(TBP8Cz•+):LA (LA = ZnII, B(C6F5)3, H+) complexes. These MnIV(O)(π-radical-cation) derivatives exhibit dramatically inhibited rates of OAT with the PAr3 substrates (k = 8.5(2) × 10−3 − 8.7 M−1 s−1), contrasting the previously observed rate increase of H-atom transfer (HAT) for MnIV(O)(TBP8Cz•+):LA with phenols. A Hammett analysis showed that the OAT reactivity for MnIV(O)(TBP8Cz•+):LA is influenced by the Lewis acid strength. Spectral redox titration of MnIV(O)(TBP8Cz•+):ZnII gives Ered = 0.69 V vs SCE, which is nearly +700 mV above its valence tautomer MnV(O)(TBP8Cz) (Ered = −0.05 V). These data suggest that the two-electron electrophilicity of the Mn(O) valence tautomers dominate OAT reactivity and do not follow the trend in one-electron redox potentials, which appear to dominate HAT reactivity. This study provides new fundamental insights regarding the relative OAT and HAT reactivity of valence tautomers such as MV(O)(porph) versus MIV(O)(porph•+) (M = Mn or Fe) found in heme enzymes.

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Synthesis and characterization of a manganese(III) porphyrin cation radical and its conversion to manganese(IV) by ligand metathesis

Abstract: bond angles, bond distances, torsional angles, positional parameters of H-atoms, general temperature factors, and structure factor amplitudes for 1 and 6(110 pages). Ordering information is given on any current masthead page.

Cited by 29 publications

References 2 publications

In-situ Fourier transform infrared spectroelectrochemical studies of the oxidation of some tetraphenylporphyrin complexes

In-situ Fourier transform infrared spectroelectrochemical studies of the oxidation of some tetraphenylporphyrin complexes

Reversible Complexation of Acetylene with (Perchlorato)cobalt(III) Porphyrins To Form a Novel Dicobalt(II) Bis(porphyrin) with a Vinylene-N,N‘ Linkage

Strong Inhibition of O-Atom Transfer Reactivity for Mn^IV(O)(π-Radical-Cation)(Lewis Acid) versus Mn^V(O) Porphyrinoid Complexes

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Synthesis and characterization of a manganese(III) porphyrin cation radical and its conversion to manganese(IV) by ligand metathesis

Abstract: bond angles, bond distances, torsional angles, positional parameters of H-atoms, general temperature factors, and structure factor amplitudes for 1 and 6(110 pages). Ordering information is given on any current masthead page.

Cited by 29 publications

References 2 publications

In-situ Fourier transform infrared spectroelectrochemical studies of the oxidation of some tetraphenylporphyrin complexes

In-situ Fourier transform infrared spectroelectrochemical studies of the oxidation of some tetraphenylporphyrin complexes

Reversible Complexation of Acetylene with (Perchlorato)cobalt(III) Porphyrins To Form a Novel Dicobalt(II) Bis(porphyrin) with a Vinylene-N,N‘ Linkage

Strong Inhibition of O-Atom Transfer Reactivity for MnIV(O)(π-Radical-Cation)(Lewis Acid) versus MnV(O) Porphyrinoid Complexes

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Strong Inhibition of O-Atom Transfer Reactivity for Mn^IV(O)(π-Radical-Cation)(Lewis Acid) versus Mn^V(O) Porphyrinoid Complexes