Clusters of the Ionic Liquid 1-Hydroxyethyl-3-methylimidazolium Picrate

From Theoretical Prediction in the Gas Phase to Experimental Evidence in the Solid State

Sumit K. Panja, Boumediene Haddad, Johannes Kiefer*

*Corresponding author for this work

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Interonic interactions determine the macroscopic properties of ionic liquids (ILs). Hence, unravelling the relationships between the microscopic and macroscopic scales is key for rational design. Combining density functional theory (DFT) calculations of isolated ion pairs and vibrational spectroscopy of the condensed phase (fluid or solid) has become a very common approach. In the present work, we make a step towards understanding how the physicochemical effects in small gas phase clusters of a hydroxyl functionalized imidazolium-picrate IL relate with the molecular structure and interactions of the corresponding solid material taking 1-hydroxyethyl-3-methylimidazolium picrate, C(2)OHmimPic, as an example. In the isolated ion pair, strong alkyl-OH center dot center dot center dot Pic hydrogen bonding interactions are found rather than the commonly observed hydrogen bonding interactions at the slightly acidic C(2)-H site of the imidazolium ring. However, this part of the cation plays an important role when clusters of ion pairs in the gas phase and inside a crystal lattice are considered. For example, in the dimeric ion-pair cluster, one centre (O*) with two interaction sites (C(2)-H-O* and alkyl OH-Pic) is observed. This configuration is suggested by single crystal X-ray diffraction (XRD), vibrational spectroscopy, and the dispersion-corrected DFT calculations. Hence, the study provides evidence for the appearance of theoretical gas phase clusters in an actual solidified ionic liquid. This ion pair dimer formation may be a general behavior of hydroxyl functionalized imidazolium ILs, but further research is needed to draw a final conclusion. Moreover, the Raman spectra confirm the exclusive gauche conformation of the hyroxyl functionalized alkyl chain.

Original languageEnglish
Pages (from-to)3061-3068
Number of pages8
JournalChemPhysChem
Volume19
Issue number22
Early online date14 Sep 2018
DOIs
Publication statusPublished - 19 Nov 2018

Keywords

  • cluster formation
  • density functional theory
  • hydrogen bonds
  • ionic liquids
  • ion-pairs
  • CH STRETCHING VIBRATIONS
  • DENSITY-FUNCTIONAL THEORY
  • ALKYL CHAIN-LENGTH
  • 1-BUTYL-3-METHYLIMIDAZOLIUM CATION
  • MOLECULAR-INTERACTIONS
  • RATIONAL DESIGN
  • CHARGED IONS
  • ANION
  • SPECTROSCOPY
  • HYDROXYL

Cite this

Clusters of the Ionic Liquid 1-Hydroxyethyl-3-methylimidazolium Picrate : From Theoretical Prediction in the Gas Phase to Experimental Evidence in the Solid State. / Panja, Sumit K.; Haddad, Boumediene; Kiefer, Johannes.

In: ChemPhysChem, Vol. 19, No. 22, 19.11.2018, p. 3061-3068.

Research output: Contribution to journalArticle

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title = "Clusters of the Ionic Liquid 1-Hydroxyethyl-3-methylimidazolium Picrate: From Theoretical Prediction in the Gas Phase to Experimental Evidence in the Solid State",
abstract = "Interonic interactions determine the macroscopic properties of ionic liquids (ILs). Hence, unravelling the relationships between the microscopic and macroscopic scales is key for rational design. Combining density functional theory (DFT) calculations of isolated ion pairs and vibrational spectroscopy of the condensed phase (fluid or solid) has become a very common approach. In the present work, we make a step towards understanding how the physicochemical effects in small gas phase clusters of a hydroxyl functionalized imidazolium-picrate IL relate with the molecular structure and interactions of the corresponding solid material taking 1-hydroxyethyl-3-methylimidazolium picrate, C(2)OHmimPic, as an example. In the isolated ion pair, strong alkyl-OH center dot center dot center dot Pic hydrogen bonding interactions are found rather than the commonly observed hydrogen bonding interactions at the slightly acidic C(2)-H site of the imidazolium ring. However, this part of the cation plays an important role when clusters of ion pairs in the gas phase and inside a crystal lattice are considered. For example, in the dimeric ion-pair cluster, one centre (O*) with two interaction sites (C(2)-H-O* and alkyl OH-Pic) is observed. This configuration is suggested by single crystal X-ray diffraction (XRD), vibrational spectroscopy, and the dispersion-corrected DFT calculations. Hence, the study provides evidence for the appearance of theoretical gas phase clusters in an actual solidified ionic liquid. This ion pair dimer formation may be a general behavior of hydroxyl functionalized imidazolium ILs, but further research is needed to draw a final conclusion. Moreover, the Raman spectra confirm the exclusive gauche conformation of the hyroxyl functionalized alkyl chain.",
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author = "Panja, {Sumit K.} and Boumediene Haddad and Johannes Kiefer",
note = "Funding Information Department of Inorganic and Physical Chemistry (IPC). Grant Number: N-PDF/2016/000041 Indian Institute of Science (IISc)",
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T1 - Clusters of the Ionic Liquid 1-Hydroxyethyl-3-methylimidazolium Picrate

T2 - From Theoretical Prediction in the Gas Phase to Experimental Evidence in the Solid State

AU - Panja, Sumit K.

AU - Haddad, Boumediene

AU - Kiefer, Johannes

N1 - Funding Information Department of Inorganic and Physical Chemistry (IPC). Grant Number: N-PDF/2016/000041 Indian Institute of Science (IISc)

PY - 2018/11/19

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N2 - Interonic interactions determine the macroscopic properties of ionic liquids (ILs). Hence, unravelling the relationships between the microscopic and macroscopic scales is key for rational design. Combining density functional theory (DFT) calculations of isolated ion pairs and vibrational spectroscopy of the condensed phase (fluid or solid) has become a very common approach. In the present work, we make a step towards understanding how the physicochemical effects in small gas phase clusters of a hydroxyl functionalized imidazolium-picrate IL relate with the molecular structure and interactions of the corresponding solid material taking 1-hydroxyethyl-3-methylimidazolium picrate, C(2)OHmimPic, as an example. In the isolated ion pair, strong alkyl-OH center dot center dot center dot Pic hydrogen bonding interactions are found rather than the commonly observed hydrogen bonding interactions at the slightly acidic C(2)-H site of the imidazolium ring. However, this part of the cation plays an important role when clusters of ion pairs in the gas phase and inside a crystal lattice are considered. For example, in the dimeric ion-pair cluster, one centre (O*) with two interaction sites (C(2)-H-O* and alkyl OH-Pic) is observed. This configuration is suggested by single crystal X-ray diffraction (XRD), vibrational spectroscopy, and the dispersion-corrected DFT calculations. Hence, the study provides evidence for the appearance of theoretical gas phase clusters in an actual solidified ionic liquid. This ion pair dimer formation may be a general behavior of hydroxyl functionalized imidazolium ILs, but further research is needed to draw a final conclusion. Moreover, the Raman spectra confirm the exclusive gauche conformation of the hyroxyl functionalized alkyl chain.

AB - Interonic interactions determine the macroscopic properties of ionic liquids (ILs). Hence, unravelling the relationships between the microscopic and macroscopic scales is key for rational design. Combining density functional theory (DFT) calculations of isolated ion pairs and vibrational spectroscopy of the condensed phase (fluid or solid) has become a very common approach. In the present work, we make a step towards understanding how the physicochemical effects in small gas phase clusters of a hydroxyl functionalized imidazolium-picrate IL relate with the molecular structure and interactions of the corresponding solid material taking 1-hydroxyethyl-3-methylimidazolium picrate, C(2)OHmimPic, as an example. In the isolated ion pair, strong alkyl-OH center dot center dot center dot Pic hydrogen bonding interactions are found rather than the commonly observed hydrogen bonding interactions at the slightly acidic C(2)-H site of the imidazolium ring. However, this part of the cation plays an important role when clusters of ion pairs in the gas phase and inside a crystal lattice are considered. For example, in the dimeric ion-pair cluster, one centre (O*) with two interaction sites (C(2)-H-O* and alkyl OH-Pic) is observed. This configuration is suggested by single crystal X-ray diffraction (XRD), vibrational spectroscopy, and the dispersion-corrected DFT calculations. Hence, the study provides evidence for the appearance of theoretical gas phase clusters in an actual solidified ionic liquid. This ion pair dimer formation may be a general behavior of hydroxyl functionalized imidazolium ILs, but further research is needed to draw a final conclusion. Moreover, the Raman spectra confirm the exclusive gauche conformation of the hyroxyl functionalized alkyl chain.

KW - cluster formation

KW - density functional theory

KW - hydrogen bonds

KW - ionic liquids

KW - ion-pairs

KW - CH STRETCHING VIBRATIONS

KW - DENSITY-FUNCTIONAL THEORY

KW - ALKYL CHAIN-LENGTH

KW - 1-BUTYL-3-METHYLIMIDAZOLIUM CATION

KW - MOLECULAR-INTERACTIONS

KW - RATIONAL DESIGN

KW - CHARGED IONS

KW - ANION

KW - SPECTROSCOPY

KW - HYDROXYL

U2 - 10.1002/cphc.201800684

DO - 10.1002/cphc.201800684

M3 - Article

VL - 19

SP - 3061

EP - 3068

JO - ChemPhysChem

JF - ChemPhysChem

SN - 1439-4235

IS - 22

ER -