Effect of Large Electrolyte Anions on the Sequential Oxidations of Bis(fulvalene)diiron Attached to Glassy Carbon by an Ethynyl Linkage

Sheridan, Matthew V.; Gamm, Paul; Schneebeli, Severin T.; Breuer, Rochus; Schmittel, Michael; Geiger, William E.

doi:10.1021/acs.langmuir.7b03649

Cited by 7 publications

(6 citation statements)

References 92 publications

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“…Comparable diminishments of modified electrode currents were observed for all the ferrocenyl systems studied. We noted similar effects for smaller vs larger electrolyte anions in the voltammetry of carbon electrodes modified by attachment of bis(fulvalene)diiron (BFD) through an ethynyl group . In the ethynyl‐BFD case, the differences in the measured peak widths and surface currents became larger in the second oxidation process (in which the dication is formed), but were already observable in the first oxidation process.…”

Section: Resultsmentioning

confidence: 70%

Anodic Oxidation of Ethynylferrocene Derivatives in Homogeneous Solution and Following Anodic Deposition onto Glassy Carbon Electrodes

et al. 2019

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Eight ferrocene derivatives linked by either an ether, amine, or phenylacetylene moiety to a terminal ethynyl group were covalently deposited on glassy carbon electrodes by anodic electrochemical methods. The lithio activation method, in which the terminal hydrogen of the ethynyl group is replaced by a lithium atom before anodic oxidation, was successfully employed in all cases. Direct oxidation of the inactivated ethynyl group also resulted in surface deposition. Surface coverages between 1×10−10 mol cm−2 and 14×10−10 mol cm−2 were achieved. Cyclic voltammetry scans of the modified electrodes in pure electrolytes differed depending on the size of the supporting electrolyte anion, as little as half the current being measured for a [B(C6F5)4]− vs. [PF6]− solution, suggesting differences in ion transport near the electrode surface. An ether‐linked ethynylferrocenium ion (5+) was isolated after electrolytic and chemical oxidation of 5 and characterized by X‐Ray crystallography as its [SbCl6]− salt.

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Section: Resultsmentioning

confidence: 70%

Anodic Oxidation of Ethynylferrocene Derivatives in Homogeneous Solution and Following Anodic Deposition onto Glassy Carbon Electrodes

et al. 2019

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“…It was generally observed that the square wave current for the second porphyrin oxidation was smaller than the first (Figure 10), a phenomenon reported previously for the two oxidations of surface-bound ethynylbis(fulvalene)diiron in [B(C 6 F 5 ) 4 ] − -based electrolyte and ascribed to mixed diffusivity of the large counteranion at the solution/surface interface. 73 Brennan et al have also reported examples of overall decreased currents for porphyrin electropolymers in solutions containing large anions. 74 In the present case, comparison with the behavior in smaller-anion electrolytes was not carried out owing to the complication of faster follow-up reactions of [H 2 1] 2+ in small-anion media.…”

Section: Resultsmentioning

confidence: 97%

Ethynylphenyl-Derivatized Free Base Porphyrins: Anodic Oxidation Processes and Covalent Grafting onto Glassy Carbon Electrodes

et al. 2019

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In six of seven cases, direct anodic oxidation of the ethynyl group of an ethynylphenylderivatized free-base porphyrin gave modified glassy carbon electrodes in which the porphyrin was strongly surface-bound, most likely in a perpendicular geometry through covalent attachment of the ethynyl group to a surface carbon atom. The porphyrins each contained an ethynylphenyl group in one meso position and varied in the groups present in the other three meso positions. Electrografted 5,10,15,20-tetrakis(ethynylphenyl)porphyrin, H21, which has ethynyl moieties in all four meso positions, has well-defined surface voltammetry and grows to multi-layer levels upon repeated cyclic voltammetry (CV) deposition scans. Multi-layering was not observed to the same degree for mono-ethynylphenyl-substituted porphyrins, and became progressively less for porphyrins having groups in the 15-meso position that were more protective against ethynyl radical attack. Clean molecular monolayer-level coverage was observed for 5-ethynylphenyl-10,20-bis(3-methoxyphenyl)-15-hexylporphyrin, H25. Owing to the fact that the ethynyl oxidation potential (1.1 to 1.5 V vs ferrocene) is more positive than that of the second macrocycle oxidation, the longevities and follow-up reactions of the porphyrin dications were also studied by CV, chemical oxidation, and optical spectroscopy in homogeneous solution. The primary follow-up products of the doubly oxidized porphyrins, whether surface-bound or in solution, were pyrrole-protonated species that were easily reduced back to the neutral porphyrin.

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“…These kind of pre‐waves at the foot of the main wave are not exclusive of the reduction of surface nitrobenzene groups because they were also observed during the reduction of other surface redox groups . In the case of the anodic oxidation of grafted groups like ferrocene, this sort of pre‐waves have not been observed …”

Section: Resultsmentioning

confidence: 98%

“…[11] In the case of the anodic oxidation of grafted groups like ferrocene, this sort of pre-waves have not been observed. [30][31][32] Therefore, the non-ideal behavior of the voltammograms obtained by reduction of the grafted film is related to the generation of nitrobenzene radical anion species, whose stability inside the grafted film can be influenced, in a first approach, by ion-pairing, hydrogen bonding and/or proton transfer processes. The probable intervention of these processes during the reduction of the grafted nitrobenzene moieties represents a high level of complexity and consequently, the intervention of any hydrogen bonding or proton transfer processes promoted by the presence of traces of water in the solvent was minimized using anhydrous acetonitrile and supporting electrolytes purified by recrystallization and dried overnight in an oven at 70°C.…”

Section: Electroactivity Of the Electrografted Nitrophenyl Groupsmentioning

confidence: 99%

Effect of Electrolyte Ions on the Formation, Electroactivity, and Rectification Properties of Films Obtained by Electrografting

2019

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The oxidation of 4‐(4‐nitrophenyl)butyrate ions in acetonitrile was used to modify glassy carbon surfaces with films bearing 3‐(4‐nitrophenyl)propyl groups. The main features of the voltammetric reduction of the grafted nitrophenyl groups were studied in two different supporting electrolytes; n‐Bu4NPF6 and Me4NPF6. The best response was obtained with the less bulky electrolyte, which was explained by the major capability of these ions to diffuse inside the channels of the grafted film, as well as the better stabilization of the radical anions generated during the reduction process. It was also shown that the films electrografted in presence of the bulky n‐Bu4NPF6 are thicker but less compact than those prepared in Me4NPF6. The amount of nitrophenyl groups in the grafted film that can be reduced depends on the size of the electrolyte ions. The permeation of the electrolyte ions inside the film channels determines also the voltammetric behavior of ferrocene as redox probe. A current rectification phenomenon was observed in acetonitrile solutions of bulky and hydrophobic electrolytes like n‐Bu4NPF6 and n‐Hx4NPF6, whose marginal inclusion inside the film channels promotes both the entrance of ferrocene and the expelling of ferrocenium ions from these ones. This phenomenon was emulated through a CEC mechanism in solution, where the diffusion inside the channels was described as single chemical equilibria.

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Effect of Large Electrolyte Anions on the Sequential Oxidations of Bis(fulvalene)diiron Attached to Glassy Carbon by an Ethynyl Linkage

Cited by 7 publications

References 92 publications

Anodic Oxidation of Ethynylferrocene Derivatives in Homogeneous Solution and Following Anodic Deposition onto Glassy Carbon Electrodes

Anodic Oxidation of Ethynylferrocene Derivatives in Homogeneous Solution and Following Anodic Deposition onto Glassy Carbon Electrodes

Ethynylphenyl-Derivatized Free Base Porphyrins: Anodic Oxidation Processes and Covalent Grafting onto Glassy Carbon Electrodes

Effect of Electrolyte Ions on the Formation, Electroactivity, and Rectification Properties of Films Obtained by Electrografting

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