Electrochemistry and Spectroelectrochemistry of 1,4-Dinitrobenzene in Acetonitrile and Room-Temperature Ionic Liquids: Ion-Pairing Effects in Mixed Solvents

Authors

Abderrahman Atifi, Marquette UniversityFollow
Michael D. Ryan, Marquette UniversityFollow

Document Type

Article

Language

eng

Format of Original

8 p.

Publication Date

7-1-2014

Publisher

American Chemical Society

Source Publication

Analytical Chemistry

Source ISSN

1520-6882

Original Item ID

DOI: 10.1021/ac5012987

Abstract

Room-temperature ionic liquids (RTILs) have been shown to have a significant effect on the redox potentials of compounds such as 1,4-dinitrobenzene (DNB), which can be reduced in two one-electron steps. The most noticeable effect is that the two one-electron waves in acetonitrile collapsed to a single two-electron wave in a RTIL such as butylmethyl imidazolium-BF₄ (BMImBF₄). In order to probe this effect over a wider range of mixed-molecular-solvent/RTIL solutions, the reduction process was studied using UV–vis spectroelectrochemistry. With the use of spectroelectrochemistry, it was possible to calculate readily the difference in E°’s between the first and second electron transfer (ΔE₁₂° = E₁° – E₂°) even when the two one-electron waves collapsed into a single two-electron wave. The spectra of the radical anion and dianion in BMImPF₆ were obtained using evolving factor analysis (EFA). Using these spectra, the concentrations of DNB, DNB^–•, and DNB^2– were calculated, and from these concentrations, the ΔE₁₂° values were calculated. Significant differences were observed when the bis(trifluoromethylsulfonyl)imide (NTf₂) anion replaced the PF₆^– anion, leading to an irreversible reduction of DNB in BMImNTf₂. The results were consistent with the protonation of DNB^2–, most likely by an ion pair between DNB^2– and BMIm⁺, which has been proposed by Minami and Fry. The differences in reactivity between the PF₆^– and NTf₂^– ionic liquids were interpreted in terms of the tight versus loose ion pairing in RTILs. The results indicated that nanostructural domains of RTILs were present in a mixed-solvent system.

Comments

Accepted version. Analytical Chemistry. Vol. 86, No. 13 (July 1, 2014): 6617-6625. DOI. © 2014 American Chemical Society. Used with permission.

Recommended Citation

Atifi, Abderrahman and Ryan, Michael D., "Electrochemistry and Spectroelectrochemistry of 1,4-Dinitrobenzene in Acetonitrile and Room-Temperature Ionic Liquids: Ion-Pairing Effects in Mixed Solvents" (2014). Chemistry Faculty Research and Publications. 479.
https://epublications.marquette.edu/chem_fac/479