Characterization of the molecular reorientational dynamics of the neat ionic liquid 1-butyl-3-methylimidazolium bromide in the super cooled state using 1H and 13C NMR spectroscopy

• Published in: Magnetic resonance in chemistry Vol. 47; no. 1; pp. 67 - 70
• Main Authors: Imanari, Mamoru, Tsuchiya, Hiroyuki, Seki, Hiroko, Nishikawa, Keiko, Tashiro, Mitsuru
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.01.2009
• Subjects: 1-butyl-3-methylimidazolium bromide; 13C NMR; ionic liquid; longitudinal relaxation time (T1); NMR; segmental motions
• ISSN: 0749-1581; 1097-458X
• DOI: 10.1002/mrc.2351

The 13C spectra and 13C longitudinal relaxation times (T1) were measured to investigate the segmental motion of the neat ionic liquid 1‐butyl‐3‐methylimidazolium bromide ([bmim]Br) in the super cooled state. The 13C signals of the imidazole ring significantly broadened at 283 K, whereas many other signals were unchanged. In the process of lowering temperature, the [bmim]Br changed to the solid state at ca 273 K without showing the rapid phase transition. Only the 13C signal of the terminal methyl group in the butyl chain was still observed at 263 K, indicating that the motion of the imidazole ring was extremely restricted, whereas the methyl group in the butyl chain was active even in the solid state. The 13C‐T1 values measured as a function of temperature also supported the discrete segmental motions of the [bmim]+ cation. Copyright © 2008 John Wiley & Sons, Ltd.