Comproportionation in the reduction of pyridinium derivatives—a combined ESR and electrochemical study

Volke, J.; Dunsch, Lothar; Volkeová, V.; Petr, Andreas; Urban, Jiřı́

doi:10.1016/s0013-4686(96)00407-0

Cited by 22 publications

(41 citation statements)

References 18 publications

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“…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: Polarographysupporting

confidence: 54%

“…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%

“…Dihydropyridines are obtained after the second electron transfer. When the 4-position of the pyridinium cation is substituted by a phenyl group, the first reduction step becomes reversible and the neutral radical generated is stable [7].…”

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: Polarographysupporting

confidence: 54%

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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“…Scheme 1 shows a possible mechanism for the reduction of the Quat monomer. Previous workers (15,20) have suggested a similar mechanism for the reduction of NADH (3)(4)(5)18), which has a very similar structure to that of the Quats studied here. Others (3-5) have proposed a series of possible reaction routes for the reduction of nicotinamide under varying pH conditions.…”

supporting

confidence: 75%

“…Others (3-5) have proposed a series of possible reaction routes for the reduction of nicotinamide under varying pH conditions. Also, a similar reduction mechanism to that in Scheme 1 for analogous substituted pyridinium compounds, but in aprotic solvents, has been suggested (18,21). In addition, it has been reported that dialkylcarbamoylpyridinium could be reduced to form 1,4-dihydropyridine in an aqueous solution (22).…”

mentioning

confidence: 57%

The reductive deposition of quaternary pyridinium corrosion inhibitor multilayers on glassy carbon electrodes

Wong¹,

Birss²

2004

Can. J. Chem.

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Abstract:The redox behaviour of several quaternary pyridinium corrosion inhibitors ("Quats") at glassy carbon (GC) electrodes has been investigated in neutral aqueous solutions. The primary emphasis is on n-butyl-3-(N-octylcarbamyl)pyridinium bromide, one of the Quats determined to have very good corrosion inhibition properties based on parallel weight loss experiments. It is demonstrated that the reduction of the Quats, which occurs in a two-electron reaction at potentials negative of -1.0 V vs. SSCE, results in the formation of a neutral product. This forms a porous film on the electrode surface, with clusters that expand and thicken as more Quat deposits, as confirmed by atomic force microscopy. The film charge density reaches a maximum of~4 mC/cm 2 , equivalent to more than 100 monolayers of Quat, after which no further Quat can be deposited, suggesting full surface coverage by a nonconducting product. The Quat multilayer can then be redissolved at potentials positive of~-0.2 V, during its oxidation back to its original solution-soluble form.Key words: quaternarized pyridinium compounds, reductive film deposition, glassy carbon, multilayer, corrosion inhibitors, cyclic voltammetry, AFM.Résumé : Opérant dans des solutions aqueuses neutres, on a étudié le comportement redox, au niveau d'électrodes de carbone vitreux (CV), de plusieurs sels de pyridinium quaternaires, des inhibiteurs de la corrosion (« Quats »). L'accent a principalement été mis sur le bromure de n-butyl-3-(N-octylcarbamyl)pyridinium, un des quatre Quats qui, sur la base d'expériences parallèles de pertes de poids, devrait présenter de très bonnes propriétés d'inhibition de la corrosion. Il a été démontré que la réduction du Quats, une réaction à deux électrons à des potentiels négatifs de -1,0 V vs. SSCE, conduit à la formation d'un produit neutre. Tel que confirmé par une microscopie de forces atomiques, celui-ci forme un film poreux sur la surface de l'électrode, avec des agrégats qui conduisent à une expansion et un épaississement avec les dépôts additionnels de Quats. La densité de charge du film atteint un maximum dẽ 4 mC/cm 2 , équivalent à plus de 100 monocouches de Quat, après quoi il ne peut plus se déposer de Quat, ce qui suggère que la surface totale est couverte par un produit qui ne conduit pas l'électricité. La multicouche de Quat peut alors être redissoute à des potentiels positifs de~-0.2 V, durant sa réoxydation à sa forme originale soluble dans la solution.Mots clés : dérivés pyridinium quaternaires, dépôt d'un film de réduction, carbone vitreux, multicouche, inhibiteurs de corrosion, voltampérométrie cyclique, AFM.[Traduit par la Rédaction] Wong et al. 1544

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