Abstract
The reactions of imidazolium-based ionic liquids having different substituent groups on the ring with hydrated electrons (e −aq ), hydroxyl radicals (•OH), and sulfate anion radicals (SO •−4 ) were investigated using nanosecond pulse radiolysis techniques. The spectra of these ionic liquids on reaction with eaq − all exhibited a similar peak at about 320 nm, and a typical peak for e −aq in aqueous ionic liquid solutions. The reaction rate constants for 1,3-disubstituted imidazolium-based ionic liquid hexafluorophosphates (BMIPF6) with eaq − were deduced to be 1010 L mol−1 s−1, however the values were lower for trisubstituted ionic liquids. For example, the rate constant for 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (BMMIBF4) was 5.5×109 L mol−1 s−1. Imidazolium-based ionic liquids reacted with hydroxyl radicals via adducts to produce a mixture of isomeric OH adducts, and the pk a value of the OH adducts was deduced to be 8.4±0.4 for 1-butyl-3-methylimdazolium tetrafluoroborate (BMIBF4). Moreover, imidazolium cations were also oxidized by SO4 •− to produce bivalent cation radicals, which exhibit a peak at 320 nm, and these rate constants are of the same order of magnitude, i.e., 109 L mol−1 s−1, except that for 1-(2-hydroxyethyl)-3-methylimdazolium tetrafluoroborate with SO4 •− (k=2.8×108 L mol−1 s−1). Theoretical calculations were carried out to estimate the structures of the products of reduction by eaq −1 and the results were related to the experimental data.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Welton T. Room-temperature ionic liquids: Solvents for synthesis and catalysis. Chem Rev, 1999, 99: 2071–2083
Rogers R D, Seddon K R. Ionic Liquids As Green Solvents: Progress and Prospects. Washington DC: American Chemical Society, 2003. 856
Dupont J. On the solid, liquid and solution structural organization of imidazolium ionic liquids. J Braz Chem Soc, 2004, 15: 341–350
Earle M J, Seddon K R. Ionic liquids. Green solvents for the future. Pure Appl Chem, 2000, 7: 1391–1398
Wasserscheid P, Welton T. Ionic Liquids in Synthesis. Weinheim: Wiley-VCH, 2003
Shkrob I A, Chemerisov S D, Wishart J F. The initial stage of radiation damage in ionic liquids and ionic liquid-based extraction systems. J Phys Chem B, 2007, 111: 11786–11793
Harmon C D, Smith W H, Costa D A. Criticality calculations for plutonium metal at room temperature in ionic liquid solutions. Radiat Phys Chem, 2001, 60: 157–159
Grodkowski J, Neta P, Wishart J F. Pulse radiolysis study of the reaction of hydrogen atoms in the ionic liquid methyltributylammonium bis (trifluoromethylsulfonyl) imide. J Phys Chem A, 2003, 107: 9794–9799
Asano A, Yang J F, Kondoh T, et al. Molar absorption coefficient and radiolytic yield of solvated electrons in diethylmethyl(2-methoxy) ammonium bis(trifluoromethanesulfonyl)imide ionic liquid. Radiat Phys Chem, 2008, 77: 1244–1247
Grodkowski J, Neta P. Reaction kinetics in the ionic liquid methy-ltributylammonium-bis(trifluoromethylsulfonyl)imide, pulse radiolysis study of CF3 radical reactions. J Phys Chem A, 2002, 106: 5468–5473
Kondoh T, Asano A, Yang J F, et al. Pulse radiolysis study of ion-species effects on the solvated electron in alkylammonium ionic liquids. Radiat Phys Chem, 2009, 78: 1157–1160
Wishart J F, Neta P. Spectrum and reactivity of the solvated electron in the ionic liquid methyltributylammonium bis(trifluoromethyls-ulfonyl)imide. J Phys Chem B, 2003, 107: 7261–7267
Behar D, Gonzalez C, Neta P. Reaction kinetics in ionic liquids: Pulse radiolysis studies of 1-butyl-3-methylimidazolium salts. J Phys Chem A, 2001, 105: 7607–7614
Wishart J F, Lall-Ramnarine S I, Raju R, et al. Effects of functional group substitution on electron spectra and solvation dynamics in a family of ionic liquids. Radiat Phys Chem, 2005, 72: 99–104
Bonhôte P, Dias A P, Papageorgiou N, et al. Hydrophobic, highly conductive ambient-temperature molten salts. Inorg Chem, 1996, 35: 1168–1178
Zhang P, Yao S D, Li H X, et al. Pulse radiolysis study on several fluoroquinolones. Radiat Phys Chem, 2011, 80: 548–553
Buxton G V, Greenstock C L, Helman W P, et al. Critical-review of rate constants for reactions of hydrated electrons, hydrogen-atoms and hydroxyl radicals (•OH/O•−) in aqueous-solution. J Phys Chem Ref Date, 1988, 17: 513–886
Rao P S, Simic M, Hayon E. Pulse-radiolysis study of imidazole and histidine in water. J Phys Chem, 1975, 79: 1260–1263
Takahashi K, Sato T, Katsumura Y, et al. Reactions of solvated electrons with imidazolium cations in ionic liquids. Radiat Phys Chem, 2008, 77: 1239–1243
Hayashi K, Nemoto Y, Akuto K, et al. Alkylated imidazolium salt electrolyte for lithium cells. J Power Source, 2005, 146: 689–692
Frisch M J, Trucks G W, Schlegel H B. Gaussian 03, Revision B.03. Pittsburgh PA: Gaussian Inc, 2003
Becke A D. Density-functional thermochemistry. 3. The role of exact exchange. J Chem Phys, 1993, 98: 5648–5652
Adams G E, Aldrich J E, Bisby R H, et al. Selective free-radical reactions with proteins and enzymes-reactions of inorganic radical anions with amino-acids. Radiat Res, 1972, 49: 278–289
Scaiano J C, Barra M, Krzywinski M, et al. Laser flash-photolysis determination of absolute rate constants for reactions of bromine atoms in solution. J Am Chem Soc, 1993, 115: 8340–8344
Michalski R, Sikora A, Adamus J, et al. Dihalide and pseudohalide radical anions as oxidizing agents in nonaqueous solvents. J Phys Chem A, 2010, 114: 861–866
Neta P, Huie E, Ross A B. Rate constants for reactions of inorganic radicals in aqueous solution. J Phys Chem Ref Data, 1988, 17: 1027–1284
Author information
Authors and Affiliations
Corresponding author
Additional information
This article is published with open access at Springerlink.com
Rights and permissions
This article is published under an open access license. Please check the 'Copyright Information' section either on this page or in the PDF for details of this license and what re-use is permitted. If your intended use exceeds what is permitted by the license or if you are unable to locate the licence and re-use information, please contact the Rights and Permissions team.
About this article
Cite this article
Fu, H., Xing, Z., Cao, X. et al. Pulse radiolysis studies of functionally substituted imidazolium-based ionic liquids. Chin. Sci. Bull. 57, 2752–2758 (2012). https://doi.org/10.1007/s11434-012-5129-8
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11434-012-5129-8