The influence of substitution on the reduction mechanism and stability of reduction intermediates in 1,1′-phenylene-, 1,1′-diphenylene- and 1,1′-polymethylene-bispyridinium dications

Volke, J.; Urban, Jiřı́; Volkeová, V.

doi:10.1016/0013-4686(92)87088-h

Cited by 21 publications

(31 citation statements)

References 17 publications

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“…As this study was dedicated, in particular, to the reduction process of the pyridinium cation, the stationary voltammetry on a solid platinum working electrode was an appropriate technique in the range of potentials from 0 to À2 V. The systems studied were MTPP-b-Py + (M = H 2 , Zn II , Ni II , Cu II or Pd II ). Their first reduction potentials match the range of values expected for the pyridinium reduction [2,6,7] (Table 2).…”

Section: Stationary Voltammetrysupporting

confidence: 64%

“…The additional wave at À0.82 V is then attributed to the electron transfer to the pyridinium cation in H 2 TPP-b-Py + . This value is in the range of those generally measured for the reduction of the pyridinium cations ðÀ1:20 V 6 E red 1=2 6 À0:70 VÞ [2,6,7]. When the pyridinium reduces first, the radical generated behaves as a neutral substituent for the porphyrin ring.…”

Section: Polarographymentioning

confidence: 89%

“…The electrochemical reduction of pyridinium cations has been extensively investigated [1][2][3][4][5][6][7][8][9][10][11], in particular as a model for the reduction of NAD + , a natural coenzyme [11,12] and of MTPP + , a biological metabolite of MPTP, a neurotoxin involved in ParkinsonÕs disease [5,[13][14][15]. Numerous results indicate that their reduction generally occurs via two distinct one-electron steps.…”

Section: Introductionmentioning

confidence: 99%

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Electrochemical reduction of l-(meso-tetraphenylporphyrin)-pyridinium cations

Brisach-Wittmeyer

Lobstein

Gross

et al. 2005

Journal of Electroanalytical Chemistry

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Section: Stationary Voltammetrysupporting

confidence: 64%

Section: Polarographymentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Electrochemical reduction of l-(meso-tetraphenylporphyrin)-pyridinium cations

Brisach-Wittmeyer

Lobstein

Gross

et al. 2005

Journal of Electroanalytical Chemistry

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“…This has been observed for a,v-dihaloalkanes (84), polymethylene-bis-sydnones (VI) (85), and some polymethylene-bis-pyridinium ions (VII) (86): H, alkyl, halogen, alkoxy, amino groups, etc., the simple ArCOR compound is reduced to an alcohol in an overall two-electron reduction process. In the medium pH range this occurs in a single two-electron wave.…”

Section: {M{rmentioning

confidence: 86%

Half a Century of Research Using Polarography

Zuman

1997

Microchemical Journal

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“…Although there are numerous examples of "extended viologens" in the literature (19)(20)(21)(22)(23)(24)(25) where their electrochemical behavior and/or propensity for electron transfer has been investigated as a result of chemical or structural modifications, there are no examples to our knowledge where IET has been investigated in the context of mechanically interlocked molecules (MIMs). The design of the bistable [2]rotaxane R 6þ ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Mechanically induced intramolecular electron transfer in a mixed-valence molecular shuttle

Barnes

Fahrenbach

Dyar

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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The kinetics and thermodynamics of intramolecular electron transfer (IET) can be subjected to redox control in a bistable [2]rotaxane comprised of a dumbbell component containing an electron-rich 1,5-dioxynaphthalene (DNP) unit and an electron-poor phenylenebridged bipyridinium (P-BIPY 2þ ) unit and a cyclobis (paraquatp-phenylene) (CBPQT 4þ ) ring component. The [2]rotaxane exists in the ground-state co-conformation (GSCC) wherein the CBPQT 4þ ring encircles the DNP unit. Reduction of the CBPQT 4þ leads to the CBPQT 2ð•þÞ diradical dication while the P-BIPY 2þ unit is reduced to its P-BIPY •þ radical cation. A radical-state co-conformation (RSCC) results from movement of the CBPQT 2ð•þÞ ring along the dumbbell to surround the P-BIPY •þ unit. This shuttling event induces IET to occur between the pyridinium redox centers of the P-BIPY •þ unit, a property which is absent between these redox centers in the free dumbbell and in the 1∶1 complex formed between the CBPQT 2ð•þÞ ring and the radical cation of methyl-phenylene-viologen (MPV •þ ). Using electron paramagnetic resonance (EPR) spectroscopy, the process of IET was investigated by monitoring the line broadening at varying temperatures and determining the rate constant (k ET ¼ 1.33 × 10 7 s −1 ) and activation energy (ΔG ‡ ¼ 1.01 kcal mol −1 ) for electron transfer. These values were compared to the corresponding values predicted, using the optical absorption spectra and Marcus-Hush theory.T he simplest organic intervalence compounds consist (1) of two redox centers (X) which are connected by a covalent bridge (b) wherein the two centers possess oxidation states that range from being equal ( nþ0.5 X − b − X nþ0.5 ) to differing by as much as one unit ( n X − b − X nþ1 ). According to the Robin-Day classification (2), there are three main types of organic compounds, which can be defined by the degree of the electronic coupling element, H, that exists between the two interacting redox centers. Compounds that exhibit low electronic coupling between each X redox center have localized charges and exhibit no intramolecular electron transfer (IET) are classified as Class I systems ( n X − b − X nþ1 , H ¼ 0), whereas those that possess a strong electronic coupling between X redox centers and undergo complete delocalization of charge and fast IET are considered Class III systems ( nþ0.5 X − b − X nþ0.5 , H ≫ 0). In between these two classifications lie Class II systems, where the electronic coupling between X redox centers is moderate, leading to a mixture of charge between each unit as well as a measurable IET event.In the 1960s, Marcus (3-6) developed a theory for electron transfer in bridged transition metal-coordinated complexes by identifying the reorganizational energy, λ, required for solvent polarization and subsequent electron transfer between two metal centers. Shortly thereafter, Hush (7-9) proposed a theoretical method that could be applied to Class II intervalence compounds by focusing on the low-energy intervalence charge transfer (IT) bands in optical abso...

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The influence of substitution on the reduction mechanism and stability of reduction intermediates in 1,1′-phenylene-, 1,1′-diphenylene- and 1,1′-polymethylene-bispyridinium dications

Cited by 21 publications

References 17 publications

Electrochemical reduction of l-(meso-tetraphenylporphyrin)-pyridinium cations

Electrochemical reduction of l-(meso-tetraphenylporphyrin)-pyridinium cations

Half a Century of Research Using Polarography

Mechanically induced intramolecular electron transfer in a mixed-valence molecular shuttle

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