High-valent iron porphyrins: synthesis, x-ray structures, .pi.-cation radical formulation, and notable magnetic properties of chloro(meso-tetraphenylporphinato)iron(III) hexachloroantimonate and bis(perchlorato)(meso-tetraphenylporphinato)iron(III)

Gans, Pierre; Buisson, G.; Duee, E.; Marchon, Jean‐Claude; Erler, Brian S.; Scholz, William F.; Reed, Christopher A.

doi:10.1021/ja00266a017

Cited by 139 publications

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“…The data presented above clearly supports previous workers' conclusions that infrared spectroscopy is a valuable tool for ascertaining the site of oxidation in TPP complexes (1,2), and further demonstrate that such useful diagnostic evidence can be obtained in situ without isolation of the oxidized complexes. In addition to the obvious factor of convenience, in-situ characterization affords a difference spectrum in which small vibrational perturbations due to oxidation of the complexes are more likely to be observed than in single spectra of isolated species.…”

Section: Discussionsupporting

confidence: 88%

“…These all displayed strong absorbance in the vicinity of 1280 cm-'. Since that time this band has been suggested (2) as the simplest of definitive criteria available for distinguishing between metal and porphyrin ring centered oxidation of tetraphenylporphyrin complexes. Other workers (3) have criticized the dse of this band as a diagnostic criterion, and produced evidence suggesting that it could arise from occluded chlorocarbon solvent molecules in the crystalline cation radicals.…”

Section: Introductionmentioning

confidence: 99%

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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: Discussionsupporting

confidence: 88%

Section: Introductionmentioning

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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“…These radicals are key intermediates in reactions involving porphyrins and metalloporphyrins, both in nature [6][7][8] and in the laboratory [9][10][11]. Therefore, a full knowledge of those redox processes is of great importance in the understanding of the role of the porphyrin macrocycle in the natural or artificial processes of photosynthesis, membrane electron transport or oxygenation catalysis.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical and spectroelectrochemical characterization of meso-tetra-alkyl porphyrins

Paliteiro

Sobral

2005

Electrochimica Acta

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A series of three meso-tetra-alkyl porphyrins (H 2 TAPs) were synthesised and their electrochemical properties were studied in dichloromethane containing either tetra-butyl ammonium perclorate (TBAP) or tetra-butyl ammonium hexafluorophosphate TBA(PF 6 ) as supporting electrolyte (SE) by cyclic voltammetry and in situ UV/vis spectroelectrochemistry. Values of E 1/2 for the recorded four redox processes of these porphyrins and of the meso-tetra-phenyl porphyrin (H 2 TPP) on glassy carbon and platinum were measured and compared. The redox data collected on the first oxidation and the first reduction processes predict that the value of (LUMO − HOMO) for the H 2 TAPs is lower than for meso-tetra-phenyl porphyrin and, therefore, that the first Q band of the electronic spectra of the H 2 TAPs is red shifted relatively to the same band in the spectrum of H 2 TPP; this shift was indeed found. The second oxidation process of the H 2 TAPs is influenced by the supporting electrolyte used and the dication then formed is consumed by an irreversible chemical reaction. The species produced in this reaction is irreversibly reduced at a considerably lower potential. The electrochemical and spectroelectrochemical data collected are consistent with the occurrence of structural distortion in the macrocycle rings of the H 2 TAPs.

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“…For a reversible system without complications, this ratio is given by In CH,Cl, containing 0.1 M TBAP, TPPFeCl undergoes a reversible one-electron oxidation with a half-wave potential of 1.13 V vs. SCE. The oxidation product has been formulated as an iron(II1) porphyrin T-cation radical (16). Figure 3 illustrates the absorbance-time transient observed for TPPFeCl during a 1 s potential pulse to 1.3 V vs. SCE, followed by a return of the potential to its initial value of 0.9 V. The data were recorded at 4 10 nm, close to the 415 nm absorbance maximum of TPPFeCl.…”

Section: Resultsmentioning

confidence: 99%

Determination of the visible spectra of electrode reaction products in strongly absorbing media by diffusion-controlled chronoabsorptometry

Jones¹,

Hinman²

1996

Can. J. Chem.

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Chronoabsorptometry under diffusion-controlled conditions has been applied to determination of the difference in molar absorptivity between electrode reaction products and reactants. The technique allows complete determination of the ultraviolet-visible spectra of reaction products that are stable on the time scale of a few hundred milliseconds. The technique was implemented with a reflectance cell that employs quartz light pipes to minimize optical absorbance of the bulk solution without obstructing the current path between counter and working electrodes. The spectrum of one-electron oxidized chloro-(5, LO, 15,20-tetraphenylporphinato)Fe(III) is determined with the new technique and compared with that obtained by conventional thin-layer spectroelectrochemistry.Key rvords: spectroelectrochemistry, chronoabsorptometry, thin-layer spectroelectrochemistry.RCsum6 : On a applique la chronoabsorptomCtrie sous des contrales par diffusion h la determination de la difference dlabsorptivitC molaire entre les rCactifs et les produits de la reaction h I'tlectrode. La technique permet de faire une determination complttte des spectres UV-visibles des produits rCactionnels qui sont stables h I'Cchelle de temps de quelques centikmes de millisecondes. La technique a CtC appliquee h l'aide d'une cellule de reflectance qui fait appel h des conduits de lumittre en quartz pour minimiser I'absorption optique de I'ensemble de la solution sans interferer avec le champ du courant entre les electrodes de rCfCrence et de travail. Faisant appel h cette technique, on a determine le spectre du chloro-(5,10,15,20-tCtraphCnylporphinate)Fe(III) oxydt par un electron et on I'a compare h celui obtenu par la technique conventionnelle de spectroClectrochimie en couche mince.Mots elks : spectro~lectrochirnie, chronoabsorptomCtrie, spectroClectrochimie en couche mince.[Traduit par la rCdaction] Determination of the uv-visible spectra of electrochemical reduction or oxidation products of highly coloured species is most frequently accomplished using thin-layer spectroelectrochemical techniques. The short optical pathlength in thin-layer cells facilitates high optical throughput, which is important in maintaining good signal-to-noise ratios. There is, however, a finite time required to achieve complete electrolysis of the thin-layer cavity due to mass transport limitations (1). In practice, even this theoretical minimum time requirement is rarely achieved because of the high solution resistance associated with the thin-layer cavity (2). This delays the onset of electrolysis at points in the thin-layer cavity positioned furthest from the counter electrode with respect to those positioned closer to the counter electrode. The effect is particularly severe in highly resistive nonaqueous media, and increases as the working electrode dimensions increase. Thin-layer techniques are thus not well suited to determining the spectra of electrochemically generated products of limited stability. Chronoabsorptometry under conditions of semi-infinite linear d...

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High-valent iron porphyrins: synthesis, x-ray structures, .pi.-cation radical formulation, and notable magnetic properties of chloro(meso-tetraphenylporphinato)iron(III) hexachloroantimonate and bis(perchlorato)(meso-tetraphenylporphinato)iron(III)

Abstract: To a solution of (Ia) in CH2Cl2 was added phenoxathiinium hexachloroantimonate, the resulting oxidation product, the complex (IIa), was shown to be an iron(III) porphyrin π‐cation radical rather than an iron(IV) compound.

Cited by 139 publications

References 0 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

Electrochemical and spectroelectrochemical characterization of meso-tetra-alkyl porphyrins

Determination of the visible spectra of electrode reaction products in strongly absorbing media by diffusion-controlled chronoabsorptometry

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