Electrochemical and electron paramagnetic resonance studies of metalloporphyrins and their electrochemical oxidation products

Wolberg, Alexander; Manassen, J.

doi:10.1021/ja00713a010

Cited by 397 publications

(174 citation statements)

References 3 publications

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“…However, the cyclic voltammogram reported for Ni(I1)TPP in benzonitrile/TBAP and that reported here using methylene dichloridel TBAP exhibit features which are atypical of most metalloporphyrins (22)(23)(24)(25). In the former case the cyclic voltammogram showed two overlapping suc-1 cessive one-electron oxidations which were separated I by not more than 100 mV.…”

Section: Discussionmentioning

confidence: 42%

Electron transport via metalloporphyrins

Johnson¹,

Niem²,

Doolphin³

1978

Can. J. Chem.

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The controlled potential electrolysis of Ni(II) meso-tetraphenylporphyrin (Ni(II)TPP) gives at room temperature the corresponding metalloporphyrin π-cation radical [Ni(II)TPP]+ •. Upon freezing a solution of the π-cation radical to 77 K an internal electron transfer occurs to give [Ni(III)TPP]+. A discussion of the routes of electron transport in heme proteins is given, and the roles of metalloporphyrin π-cation radicals in electron transport is evaluated.

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Section: Discussionmentioning

confidence: 42%

Electron transport via metalloporphyrins

Johnson¹,

Niem²,

Doolphin³

1978

Can. J. Chem.

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“…For the respective cases, one reversible wave and two or three successive waves (not shown) were obtained for the following electrode reactions: 35,42 […”

Section: Resultsmentioning

confidence: 99%

A True Electron-Transfer Reaction between 5,10,15,20-Tetraphenylporphyrinato Cadmium(II) and the Hexacyanoferrate Couple at the Nitrobenzene/Water Interface

et al. 2004

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A variety of electrochemical techniques including cyclic voltammetry, 5,6 current scan polarography, 7 the a.c. impedance method, 8 scanning electrochemical microscopy (SECM), [9][10][11][12][13][14] in situ total internal reflection, 15 and laser trapping of a single oil droplet 16 have been introduced in this field. These studies have shown that reaction mechanisms of ET at the O/W interface can be classified into two major categories: i.e., the ion-transfer (IT) mechanism and the ET mechanism. The former involves an IT process of the ionic product of a homogeneous ET in one phase (usually, the W phase). The well-known ferrocene (O)-hexacyanoferrate (W) system 5 has recently been found to come into the IT mechanism, where the ET occurs "homogeneously" in the W phase and the IT of ferricenium cation as the reaction product is responsible for the current flowing through the interface.17 A biomimetic ET system between ascorbate (W) and chloranil (O), first reported by Suzuki et al., 18 has also been shown to belong to the category of the IT mechanism. [19][20][21][22][23] In these ET systems that belong to the IT mechanism, redox species in the O phase do not seem to be very hydrophobic (usually, they have their partition coefficients into the O phase KD < 10 4 ), so that they may give rise to a homogeneous ET in the W phase, rather than a heterogeneous ET due to molecular collision at the O/W interface.On the other hand, a highly hydrophobic redox species can show a heterogeneous ET at an O/W interface. Such a "true" ET was first reported by Geblewicz and Schiffrin, 6 who used an extremely hydrophobic, lutetium diphthalocyanine complex as a redox species in 1,2-dichloroethane. They observed a welldefined voltammetric wave for a plausible, heterogeneous ET at the O/W interface. In subsequent studies, other hydrophobic organometallic compounds including tin diphthalocyanine 24 and iron and ruthenium tetraphenylporphyrins 25 were also claimed to show true ET's in the absence of possible IT. These experimental studies then stimulated theoretical studies on the kinetics of ET at O/W interfaces. [26][27][28][29][30][31][32] Then, the applicability of the theory by Marcus [26][27][28][29][30] has been tested by means of the a.c. impedance method 8 and SECM. 9-14 Although these kinetic studies generally supported the Marcus theory, it seems premature to accept the validity of the theory, because there is not very much data, and because heterogeneous ET's at O/W interfaces are often complicated by unwanted reactions, such as the above-mentioned homogeneous ET's, decomposition reactions with supporting electrolytes, interfacial adsorption of redox species, etc. 33 In this study, we focused on metal complexes of 5,10,15,20-tetraphenylporphyrin (TPP) for redox species in the O phase. Since the TPP complexes are sufficiently hydrophobic, they were expected to give rise to a true ET at an O/W interface. Also, their redox potentials, in contrast to those of phthalocyanine metal complexes, 34 are very much dependent on the ce...

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“…Representative data presented in Table 1 emphasize iron and manganese because of their intrinsic interest and because they have been comparatively neglected in previous studies (10,11). Also included, for comparative purposes, are data for some analogous porphyrin complexes.…”

Section: Resultsmentioning

confidence: 99%

Redox potentials of metal phthalocyanines in non-aqueous media

Lever¹,

Wilshire²

1976

Can. J. Chem.

100

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A study of the redox potentials of a range of metal phthalocyanines in non-aqueous media compared with analogous data for some porphyrin complexes provides evidence for extensive back donation in metallophthalocyanines. The potentials for some couples are exceedingly sensitive to axial ligation. It is suggested that this sensitivity may be used to 'tune' a redox couple for a specific purpose such as designing a reversible oxygen breathing system.

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Electrochemical and electron paramagnetic resonance studies of metalloporphyrins and their electrochemical oxidation products

Cited by 397 publications

References 3 publications

Electron transport via metalloporphyrins

Electron transport via metalloporphyrins

A True Electron-Transfer Reaction between 5,10,15,20-Tetraphenylporphyrinato Cadmium(II) and the Hexacyanoferrate Couple at the Nitrobenzene/Water Interface

Redox potentials of metal phthalocyanines in non-aqueous media

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