Electrochemistry in media of exceptionally low polarity: Voltammetry with a fluorous solvent

Abstract

This work demonstrates the first cyclic voltammetry in a perfluorocarbon solvent without use of a cosolvent. The novel electrolyte tetrabutylammonium tetrakis [3,5-bis(perfluorohexyl)phenyl]borate (NBu 4 BArF 104 ; 80 mM) allows for voltammetry of ferrocene in perfluoro(methylcyclohexane) by lowering the specific resistance to Ω268 k cm at 20.8 °C. Despite significant solution resistance, the resulting voltammograms can be fitted quantitatively without difficulty. The thus determined standard electron transfer rate constant, k°, for the oxidation of ferrocene in perfluoro (methylcyclohexane) is somewhat smaller than for many solvents commonly used in electrochemistry, but can be explained readily as the result of the viscosity and size of the solvent using Marcus theory. Dielectric dispersion spectroscopy verifies that addition of NBu 4 BArF 104 does not significantly raise the overall polarity of the solution over that of neat perfluoro (methylcyclohexane).

Facile Separation, Spectroscopic Identification, and Electrochemical Properties of Higher Trifluoromethylated Derivatives of [70]Fullerene

“…More promising were perfluorinated solvents such as hexafluorobenzene and perfluorodecalin, but they failed to provide sufficient solubility of common Bu 4 N + ‐based support electrolytes. We expect that the complications can be overcome in the future through the use of perfluorinated support electrolytes in combination with fluorous solvents.…”

“…Additional CV experiments under varied conditions (e.g.,1 ,2,4trichlorobenzene as solvent, prolonged sonification, and heating on dissolution) have not proved successful either.M ore promising were perfluorinated solvents such as hexafluorobenzene and perfluorodecalin, but they failed to provide sufficient solubility of common Bu 4 N + -based support electrolytes. We expect that the complications can be overcome in the future through the use of perfluorinated support electrolytes [38] in combination with fluorous solvents. Within the isomeric series of trifluoromethylfullerenes of a given composition, one can observe remarkable variation in the first reduction potential ( Table 2), which reflects ac onsiderable differencei nt he electronic structure.…”

Taming the Cationic Beast: Novel Developments in the Synthesis and Application of Weakly Coordinating Anions

“…In all cases, the WCAs are significantly more conductive, and in the case of [Al(OC(H)(CF 3 ) 2 ) 4 ] − even have the potential for use in toluene . The more bespoke [B(Ar Rf ) 4 ] − ion (where Rf=(CF 2 ) 5 CF 3 ) has been shown to permit the use of perfluorinated solvents of very low polarity . Furthermore, the significantly reduced nucleophilicity of WCAs towards the cationic products of oxidation result in increased cation stability.…”

“…[437,438] In all cases,the WCAsare significantly more conductive,and in the case of [Al(OC(H)(CF 3 ) 2 ) 4 ] À even have the potential for use in toluene. [439,440] Furthermore,t he significantly reduced nucleophilicity of WCAst owards the cationic products of oxidation result in increased cation stability.T he use of aw eakly nucleophilic WCA (e.g. [439,440] Furthermore,t he significantly reduced nucleophilicity of WCAst owards the cationic products of oxidation result in increased cation stability.T he use of aw eakly nucleophilic WCA (e.g.…”

“…[437] Them ore bespoke [B(Ar Rf ) 4 ] À ion (where Rf = (CF 2 ) 5 CF 3 )h as been shown to permit the use of perfluorinated solvents of very low polarity. [439,440] Furthermore,t he significantly reduced nucleophilicity of WCAst owards the cationic products of oxidation result in increased cation stability.T he use of aw eakly nucleophilic WCA (e.g. [ B(Ar CF3 ) 4 ] À ,[ B(C 6 F 5 ) 4 ] À ,o r[ Al-(OR F ) 4 ] À )c ontaining electrolyte has been shown to permit the reversible one-electron oxidation of Cp 2 Ru, rather than the single irreversible two-electron process reported for traditional anions.…”