Dependence of the Electrochemical Redox Properties of Fullerenes on Ionic Liquids

Abstract

Control of the electrochemical properties of fullerenes via the chemical modification approach has attracted considerable attention. However, surface modification of fullerene cages with various functional groups can lead to the destruction of their original structures. Herein, we report a simple approach for controlling the electrochemical properties of fullerene thin films formed on Au(111) electrodes in various ionic liquids (ILs). A total of eight reversible redox couples for six reductive and two oxidative processes were observed for fullerenes in ammonium- and pyrrolidinium-based ILs. The redox potentials, the differences between two successive redox potentials, the average values of these potential differences for fullerene reduction, and the electrochemical band gaps of fullerene films in various ILs were found to depend on the cation and its alkyl chain length, the anion, and the chemical structure of the fullerene. Highly charged C anions were reduced more easily than C anions. An increase in the alkyl chain length of the cation led to an increase in the average potential difference between two successive redox potentials for fullerene reduction. The results indicate that the electrochemical band gaps of fullerenes can be manipulated using ILs with appropriate anions, which can be determined based on the size of the anion and the charge distribution.

Multi‐Redox Active Carbons and Hydrocarbons: Control of their Redox Properties and Potential Applications

“…During electrolysis, the electrolyte solution around the working electrode can be stirred to improve the efficiency of reduction or oxidation. This method has been reportedly useful for fullerenes because their charged species readily dissolve in organic solvents and ILs [73–78] …”

“…The use of ILs has the potential to solve the aforementioned issue. Generally, ILs have a wide E pw (see Figure 2), [76,81] which can be adjusted by changing the cations and anions. With fixed counter ions, E pw follows the order: imidazolium<pyrrolidinium<ammonium and halide<triflate<bis(trifluoromethylsulfonyl)amide ([Tf 2 N] − ) [71] .…”

“…By contrast, we investigated the redox properties of fullerenes in ILs [76–78] . The use of ILs enabled eight redox reactions of C 60 and C 70 thin films (six reduction and two oxidation reactions) at room temperature [76] .…”

“…By contrast, we investigated the redox properties of fullerenes in ILs [76–78] . The use of ILs enabled eight redox reactions of C 60 and C 70 thin films (six reduction and two oxidation reactions) at room temperature [76] . Furthermore, the redox potentials and electrochemical stability of fullerene thin films were dependent on cations and anions of ILs (Figures 4 and 5).…”

Immobilization of fullerene C60 at cathodically polarized glassy carbon for the generation of thin nucleophilic layers and their carboxylation and alkylation

“…Echegoyen [3,4] reported that C 60 shows six successive reversible cathodic transitions within the range -1…-3.3 V (vs Fc + /Fc) in toluene-acetonitrile. More recently [5][6][7][8][9][10], other reports were published, using aprotic polar solvents such as acetonitrile (ACN) and dimethylformamide (DMF), that are easier to handle despite the difficulty of keeping the electrolytes sufficiently dry during the experiments. Unfortunately, the modifications of C 60 via any cathodic process affecting its initial structure led to a profound loss of the cathodic activity at the potentials lower than -2 V, which therefore ruins any possibility of using fullerenes for Journal Pre-proof building (via grafting procedure) modified solid surfaces.…”