The role of the C2 position in interionic interactions of imidazolium based ionic liquids

a vibrational and NMR spectroscopic study

Kristina Noack, Peter S Schulz, Natalia Paape, Johannes Kiefer, Peter Wasserscheid, Alfred Leipertz

Research output: Contribution to journalArticle

182 Citations (Scopus)

Abstract

Methylation of the C2 position of 1,3-dialkylimidazolium based ionic liquids disrupts the predominant hydrogen-bonding interaction between cation and anion leading to unexpected changes of the physicochemical properties. We found the viscosity of 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imide [C(2)C(1)C(1)Im][Tf2N], for example, to be about three times higher than that of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [C(2)C(1)Im][Tf2N]. In order to explain these macroscopic changes upon methylation we investigated the vibrational as well as the magnetic resonance structure of [Tf2N](-) salts involving the cations 1-ethyl-3-methylimidazolium [C(2)C(1)Im](+), 1-ethyl-2,3-dimethylimidazolium [C(2)C(1)C(1)Im](+), 1-butyl-3-methylimidazolium [C(4)C(1)Im](+), and 1-butyl-2,3-dimethylimidazolium [C(4)C(1)C(1)Im](+) by means of Fourier-transform infrared (FTIR), Raman and C-13 NMR as well as H-1 NMR spectroscopy aiming a better microscopic understanding of the cation-anion interaction. To reveal the impact of methylating the C2 position and changing the alkyl side chain length of the imidazolium a detailed assignment of the individual peaks is followed by a comparative discussion of the spectral features also considering already published work. Our spectroscopic findings deduce electron density changes leading to changes in the position and strength of interionic interactions and reduced configurational variations. Both facts are represented on a macroscopic level by the viscosity and melting point. Therefore changes on a macroscopic level clearly express molecular alterations which in turn can be observed using spectroscopic methods as Raman, IR and NMR.
Original languageEnglish
Pages (from-to)14153-14161
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume12
Issue number42
Early online date27 Sep 2010
DOIs
Publication statusPublished - 14 Nov 2010

Fingerprint

Ionic Liquids
Cations
methylation
Methylation
imides
Nuclear magnetic resonance
cations
nuclear magnetic resonance
Anions
liquids
Viscosity
viscosity
Imides
anions
interactions
Magnetic resonance
Chain length
Nuclear magnetic resonance spectroscopy
melting points
Carrier concentration

Cite this

The role of the C2 position in interionic interactions of imidazolium based ionic liquids : a vibrational and NMR spectroscopic study. / Noack, Kristina; Schulz, Peter S; Paape, Natalia; Kiefer, Johannes; Wasserscheid, Peter; Leipertz, Alfred.

In: Physical Chemistry Chemical Physics, Vol. 12, No. 42, 14.11.2010, p. 14153-14161.

Research output: Contribution to journalArticle

Noack, Kristina ; Schulz, Peter S ; Paape, Natalia ; Kiefer, Johannes ; Wasserscheid, Peter ; Leipertz, Alfred. / The role of the C2 position in interionic interactions of imidazolium based ionic liquids : a vibrational and NMR spectroscopic study. In: Physical Chemistry Chemical Physics. 2010 ; Vol. 12, No. 42. pp. 14153-14161.
@article{bb01b620853d4288bb837c74a41d45e8,
title = "The role of the C2 position in interionic interactions of imidazolium based ionic liquids: a vibrational and NMR spectroscopic study",
abstract = "Methylation of the C2 position of 1,3-dialkylimidazolium based ionic liquids disrupts the predominant hydrogen-bonding interaction between cation and anion leading to unexpected changes of the physicochemical properties. We found the viscosity of 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imide [C(2)C(1)C(1)Im][Tf2N], for example, to be about three times higher than that of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [C(2)C(1)Im][Tf2N]. In order to explain these macroscopic changes upon methylation we investigated the vibrational as well as the magnetic resonance structure of [Tf2N](-) salts involving the cations 1-ethyl-3-methylimidazolium [C(2)C(1)Im](+), 1-ethyl-2,3-dimethylimidazolium [C(2)C(1)C(1)Im](+), 1-butyl-3-methylimidazolium [C(4)C(1)Im](+), and 1-butyl-2,3-dimethylimidazolium [C(4)C(1)C(1)Im](+) by means of Fourier-transform infrared (FTIR), Raman and C-13 NMR as well as H-1 NMR spectroscopy aiming a better microscopic understanding of the cation-anion interaction. To reveal the impact of methylating the C2 position and changing the alkyl side chain length of the imidazolium a detailed assignment of the individual peaks is followed by a comparative discussion of the spectral features also considering already published work. Our spectroscopic findings deduce electron density changes leading to changes in the position and strength of interionic interactions and reduced configurational variations. Both facts are represented on a macroscopic level by the viscosity and melting point. Therefore changes on a macroscopic level clearly express molecular alterations which in turn can be observed using spectroscopic methods as Raman, IR and NMR.",
author = "Kristina Noack and Schulz, {Peter S} and Natalia Paape and Johannes Kiefer and Peter Wasserscheid and Alfred Leipertz",
year = "2010",
month = "11",
day = "14",
doi = "10.1039/c0cp00486c",
language = "English",
volume = "12",
pages = "14153--14161",
journal = "Physical Chemistry Chemical Physics",
issn = "1463-9076",
publisher = "ROYAL SOC CHEMISTRY",
number = "42",

}

TY - JOUR

T1 - The role of the C2 position in interionic interactions of imidazolium based ionic liquids

T2 - a vibrational and NMR spectroscopic study

AU - Noack, Kristina

AU - Schulz, Peter S

AU - Paape, Natalia

AU - Kiefer, Johannes

AU - Wasserscheid, Peter

AU - Leipertz, Alfred

PY - 2010/11/14

Y1 - 2010/11/14

N2 - Methylation of the C2 position of 1,3-dialkylimidazolium based ionic liquids disrupts the predominant hydrogen-bonding interaction between cation and anion leading to unexpected changes of the physicochemical properties. We found the viscosity of 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imide [C(2)C(1)C(1)Im][Tf2N], for example, to be about three times higher than that of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [C(2)C(1)Im][Tf2N]. In order to explain these macroscopic changes upon methylation we investigated the vibrational as well as the magnetic resonance structure of [Tf2N](-) salts involving the cations 1-ethyl-3-methylimidazolium [C(2)C(1)Im](+), 1-ethyl-2,3-dimethylimidazolium [C(2)C(1)C(1)Im](+), 1-butyl-3-methylimidazolium [C(4)C(1)Im](+), and 1-butyl-2,3-dimethylimidazolium [C(4)C(1)C(1)Im](+) by means of Fourier-transform infrared (FTIR), Raman and C-13 NMR as well as H-1 NMR spectroscopy aiming a better microscopic understanding of the cation-anion interaction. To reveal the impact of methylating the C2 position and changing the alkyl side chain length of the imidazolium a detailed assignment of the individual peaks is followed by a comparative discussion of the spectral features also considering already published work. Our spectroscopic findings deduce electron density changes leading to changes in the position and strength of interionic interactions and reduced configurational variations. Both facts are represented on a macroscopic level by the viscosity and melting point. Therefore changes on a macroscopic level clearly express molecular alterations which in turn can be observed using spectroscopic methods as Raman, IR and NMR.

AB - Methylation of the C2 position of 1,3-dialkylimidazolium based ionic liquids disrupts the predominant hydrogen-bonding interaction between cation and anion leading to unexpected changes of the physicochemical properties. We found the viscosity of 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imide [C(2)C(1)C(1)Im][Tf2N], for example, to be about three times higher than that of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [C(2)C(1)Im][Tf2N]. In order to explain these macroscopic changes upon methylation we investigated the vibrational as well as the magnetic resonance structure of [Tf2N](-) salts involving the cations 1-ethyl-3-methylimidazolium [C(2)C(1)Im](+), 1-ethyl-2,3-dimethylimidazolium [C(2)C(1)C(1)Im](+), 1-butyl-3-methylimidazolium [C(4)C(1)Im](+), and 1-butyl-2,3-dimethylimidazolium [C(4)C(1)C(1)Im](+) by means of Fourier-transform infrared (FTIR), Raman and C-13 NMR as well as H-1 NMR spectroscopy aiming a better microscopic understanding of the cation-anion interaction. To reveal the impact of methylating the C2 position and changing the alkyl side chain length of the imidazolium a detailed assignment of the individual peaks is followed by a comparative discussion of the spectral features also considering already published work. Our spectroscopic findings deduce electron density changes leading to changes in the position and strength of interionic interactions and reduced configurational variations. Both facts are represented on a macroscopic level by the viscosity and melting point. Therefore changes on a macroscopic level clearly express molecular alterations which in turn can be observed using spectroscopic methods as Raman, IR and NMR.

U2 - 10.1039/c0cp00486c

DO - 10.1039/c0cp00486c

M3 - Article

VL - 12

SP - 14153

EP - 14161

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

SN - 1463-9076

IS - 42

ER -