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Comparison of Low‐Frequency Spectra between Aromatic and Nonaromatic Cation Based Ionic Liquids Using Femtosecond Raman‐Induced Kerr Effect Spectroscopy
Author(s) -
Shirota Hideaki
Publication year - 2012
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201100731
Subject(s) - ionic liquid , polarizability , raman spectroscopy , chemistry , ionic bonding , kerr effect , femtosecond , spectroscopy , spectral line , ion , analytical chemistry (journal) , chemical physics , organic chemistry , molecule , optics , laser , physics , astronomy , nonlinear system , quantum mechanics , catalysis
In this minireview, the features of low‐frequency spectra within the frequency range 0–200 cm −1 for aromatic and nonaromatic cation based ionic liquids obtained by femtosecond Raman‐induced Kerr effect spectroscopy are reviewed. For aromatic cation based ionic liquids, the aromatic group of the cations is largely responsible for the spectral line shape due to their larger polarizability anisotropy volume and more polarizable nature than nonaromatic cations. The low‐frequency Kerr spectra are also compared with the bulk properties of the ionic liquids. The differences in the relationship of the first moment of the low‐frequency spectrum band and the bulk properties between the aromatic and nonaromatic cation based ionic liquids with respect to the natures of constituent ions and microscopic aspects are discussed. For aromatic cation based ionic liquids, the ionic region is more pronounced than the nonpolar region in their low‐frequency Kerr spectra. In contrast, the ionic and nonpolar regions of nonaromatic cation based ionic liquids are likely to be captured due to the weaker signal of the cationic region. Also, the low‐frequency Kerr spectra of the nonaromatic analogues are influenced by their weaker segregation as compared to aromatic cation based ionic liquids.