Polarographic Reduction of Porphyrins and Electron Spin Resonance of Porphyrin Anions<sup>1</sup>

Felton, R. H.; Linschitz, Henry

doi:10.1021/ja00958a004

Cited by 218 publications

(85 citation statements)

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“…The current rose to levels that are not consistent with the amount of porphyrin present in solution. With addition of 10 III of 3% acid, the peak current for the reduction of CuTPP had risen 22 fold. Further additions continued to increase the peak current until it was off-scale.…”

Section: Methodsmentioning

confidence: 99%

“…The measurements were usually In non-aqueous media, free base tetraphenylporphyrins, octaethylporphyrins, etioporphyrins, and protoporphyrin dimethyl esters are all reduced in 2 one-electron steps to the IT-radical anion and then to the dianion. [21][22][23][24] Similarly, oxidation of free-base porphyrins yields first a IT-radical cation and then the dication. 25 -28 The site of oxidation or reduction and the identity of the final products were established through the use of electron spin resonance spectroscopy (ESR) 22,25 and absorption spectroscopy, 24,28 as well as by noting certain regularities in electrochemical behavior.…”

Section: Electrochemical Reactivity Of Porphyrinsmentioning

confidence: 99%

“…[21][22][23][24] Similarly, oxidation of free-base porphyrins yields first a IT-radical cation and then the dication. 25 -28 The site of oxidation or reduction and the identity of the final products were established through the use of electron spin resonance spectroscopy (ESR) 22,25 and absorption spectroscopy, 24,28 as well as by noting certain regularities in electrochemical behavior. 21 ,23 Further reductions are possible but are irreversible and involve disproportionation and simultaneous uptake of protons from solution.…”

Section: Electrochemical Reactivity Of Porphyrinsmentioning

confidence: 99%

“…E = EOTAPp(unprotonated) -EOTAPp(protonated) [21] = (EO TPP + 4.cr x ·p) -(EO TPP + 4 e cr y .p) [22] = 4 e p.(cr x -cry) [23] Calculating~E for the amino vs. ammonium substituents, one finds that Hammett substituent constants lead one to expect a shift in reduction potential of 228 mV from TAPP to TAPP+ 4 .…”

Section: Ionization Effects On Electrochemistrymentioning

confidence: 99%

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Solvent and Substituent Effects on the Redox Potentials of Several Substituted Tetraphenylporphyrins

Ransdell

2000

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Some specific conclusions are summarized. 1.The usefulness of linear free energy relationships in correlating variations in redox potentials with changes in substituent was confirmed with two exceptions. Two of the porphyrins were shown to undergo a different electrochemical oxidation mechanism than the remaining porphyrins, and another porphyrin was shown to be more difficult to reduce than predicted on the basis of its substituent constant. 2.Solvent effects, here investigated as the effect of added water on the reduction potential of tetraaminophenylporphyrin in DMSO, were demonstrated to correlate with the Dimroth-Reichardt solvent parameter, E T , determined experimentally for each water-DMSO mix. 2. LIST OF TABLES 3.4. 5.6. 7.8. 9.10. 11.12. can be used to drive the photochemical splitting of water into hydrogen gas and oxygen gas. This is illustrated in Figure 1, where S is an absorbing chromophore, A is an electron acceptor, and 0 is an electron donor. Figure 3), the resultant straight line can be written as: LIST OF FIGURESwhere p is the slope of the plot and A is the Y-intercept, which is equal to log k h '. As before, k h ' is the value of k h for the unsubstituted ethyl benzoate. This notation is used instead of that of Hammett, who used Ki 0 and k h 0 in their place, in order to avoid confusion when correlating EO values.Hammett then proposed choosing one system as the reference K or k, and recommended using Ki for substituted benzoic acids since at the time those constants were readily available and easily measured with good precision. A general relationship between a given rate or equilibrium constant k and the reference system Ki can be described using the equation below: [ 2] Hammett then went on to define C1 (x), the substituent constant for substituent X, as below:log KjK' Ionization Figure 3. Comparison of hydrolysis rates of esters with ionization constant~of acids for m-and pbenzoic acid derivatives.[ 3 ]Substituting equation [3] into equation [2] relating the generic k to Ki for benzoic acids yields the following equation:or,[5 ] Given the existence of a quantitative correlation, the fact that it is linear in the logarithms can be no mere accident; for the linear relationship between the logarithms of the constants is equivalent to a relationship between the quantities -RT In k, which are the free energies of reaction or of activation. From the definition of an equilibrium constant, we know that~Go = -RTeln K =.-nFEo. From this it follows that:In K = (nF/RT)eEO or converting to base 10, log K = (nF/2.303RT)eEO [7] [ 8 ] 8Expressing equation [8] in the form of equation [4] yields the following equation: [9 ] where EO' is EO for unsubstituted tetraphenylporphyrin. Model Porphryins For Thin-Film MembranesThe assembly of molecular components into photochemical molecular devices is the goal of a new field of research. 11Many useful applications are possible, such as photochemical synthesis, photochromism, and photodecomposition. Applications such as these may not require an organiz...

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Section: Methodsmentioning

confidence: 99%

Section: Electrochemical Reactivity Of Porphyrinsmentioning

confidence: 99%

Section: Electrochemical Reactivity Of Porphyrinsmentioning

confidence: 99%

Section: Ionization Effects On Electrochemistrymentioning

confidence: 99%

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Solvent and Substituent Effects on the Redox Potentials of Several Substituted Tetraphenylporphyrins

Ransdell

2000

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“…The reaction of metalloporphyrins with aromatic radical anions was first investigated by Closs and Closs. 26 Two subsequent 50,51 one-electron reductions yielding the dianion can be followed by uv-vis and esr spectroscopy. 26,47 Addition of 1 mole of methanol to the dianion yields the anion of type 3, which can be considered as the conjugated base of either a phlorin or a porphodimethene.…”

Section: Chemical Reduction To Interrupted Systemsmentioning

confidence: 99%

Synthesis and Stereochemistry of Hydroporphyrins

Scheer¹

1978

The Porphyrins

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Electrochemically driven introduction of copper ions into the ring of 5,10,15,20-tetraphenyl-21H, 23H-porphyrin mechanically attached as solid microparticles to a graphite electrode

Zhuang

Scholz

2000

J. Porphyrins Phthalocyanines

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Upon cyclic electrochemical polarization, traces of 5,10,15,20-tetraphenyl-21H,23H-porphyrin (H2TPP), which have been mechanically transferred to the surface of a paraffin-impregnated graphite electrode, incorporate copper ions from aqueous solution into the porphyrin ring to form CuTPP . The mechanism of formation of copper porphyrin and the catalytic action of the latter on the electroreduction of oxygen were studied by cyclic voltammetry and square-wave voltammetry. In solid CuTPP the Cu II/ Cu I system is electrochemically active according to the following insertion electrochemical reaction: [Formula: see text]. When the CuTPP is dissolved in organic solvents, the central copper ion does not show any electrochemical activity in the accessible potential range.

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Polarographic Reduction of Porphyrins and Electron Spin Resonance of Porphyrin Anions¹

Cited by 218 publications

References 3 publications

Solvent and Substituent Effects on the Redox Potentials of Several Substituted Tetraphenylporphyrins

Solvent and Substituent Effects on the Redox Potentials of Several Substituted Tetraphenylporphyrins

Synthesis and Stereochemistry of Hydroporphyrins

Electrochemically driven introduction of copper ions into the ring of 5,10,15,20-tetraphenyl-21H, 23H-porphyrin mechanically attached as solid microparticles to a graphite electrode

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Polarographic Reduction of Porphyrins and Electron Spin Resonance of Porphyrin Anions1

Cited by 218 publications

References 3 publications

Solvent and Substituent Effects on the Redox Potentials of Several Substituted Tetraphenylporphyrins

Solvent and Substituent Effects on the Redox Potentials of Several Substituted Tetraphenylporphyrins

Synthesis and Stereochemistry of Hydroporphyrins

Electrochemically driven introduction of copper ions into the ring of 5,10,15,20-tetraphenyl-21H, 23H-porphyrin mechanically attached as solid microparticles to a graphite electrode

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Polarographic Reduction of Porphyrins and Electron Spin Resonance of Porphyrin Anions¹