Low-Frequency Spectra of Metallocenium Ionic Liquids Studied by Terahertz Time-Domain Spectroscopy

Abstract

Terahertz (THz) time-domain spectroscopic measurements have been done on five novel metallocenium ionic liquids based on the electro-optic sampling method. The study covered the spectral range from 10 to 85 cm(-1). The complex dielectric spectra were broad and dispersive in nature, and the imaginary part of the dielectric constant consisting of part of the dielectric constant was simulated with different combinations of model functions to unravel the intermolecular dynamics. We compared our results with the previous results on the other ionic liquid. It was revealed that the librational motion of the cations as well as the interion vibration between the cations and the anions are responsible for observed dynamics in THz region. No intramolecular vibrational mode has been found in the low-frequency region.

Ionic Liquids of Cationic Sandwich Complexes

“…The preparation and melting points of several ferrocenium and cobaltocenium ILs, has already been reported in a preliminary account of this work 17. In separate papers, we reported the dynamics of the metallocenium ILs investigated by terahertz time‐domain spectroscopy,18 the magnetic properties of octamethylferrocenium ILs,19 and the chemical reactivities of half‐metallocenium ILs 20…”

Ferrocenyl-phosphonium ionic liquids – synthesis, characterisation and electrochemistry

“…9 was isolated as a mixture of three isomers. Dibutylcyclopenta-2,4-dienyl phosphine: 31 (1-Ferrocenylethyl)tributylphosphonium bis(trifluoromethanesulfonyl)imide (11) [FcCHMePBu 3 ]NTf 2 . 350 mg 1-hydroxyethylferrocene (1.52 mmol, 1.0 eq.)…”

“…Ionic liquids based on organosubstituted ferrocenium cations [FcR]X have been investigated, which however after reduction lose their ionic character and retention properties in electrolytes. 10 Furthermore low-melting heteroleptic sandwich compounds of the form [(C 5 H 4 R)Fe(arene)]X came into focus 11 but they tend to be not robust enough against light.…”

Pressure and temperature effects on intermolecular vibrational dynamics of ionic liquids

“…Motivated by both the technological applications and the fundamental scientific issues, a growing literature on structure and dynamics of ionic liquids has become available in the last decade using different spectroscopic techniques. 5,[10][11][12][13][14][15][16][17][18] In the low-frequency range, ionic liquids dynamics have been investigated by optical Kerr effect (OKE), [10][11][12][13][14][15] far-infrared, 16,17 terahertz time domain, 16,18 dielectric relaxation, 13,14 and Raman spectroscopies. 16 OKE spectroscopy has been the most commonly used technique for unraveling the intermolecular vibrational dynamics of ionic liquids within the THz range.…”