title: Complementing Crystallography with Ultralow-Frequency Raman Spectroscopy: Structural Insights into Nitrile-Functionalized Ionic Liquids.
abstract: Functionalized ionic liquids are a subclass of ionic liquids that are tailored for a specific application. Structural characterization in both solid and liquid phases is central to understanding their physical properties. Here, we used ultralow-frequency Raman spectroscopy, which can measure Raman spectra down to approximately 5 cm(-1) , to study the structures and physical properties of 1-(4-cyanobenzyl)-3-methylimidazolium salts with five different anions. A comparison of the observed low-frequency Raman spectral patterns enabled us to predict the crystal symmetry of one of the synthesized salts for which single-crystal X-ray diffraction data were unobtainable. Real-time tracking of the low-frequency Raman spectral changes during melting revealed peak shifts indicative of different degrees of microscopic heterogeneity in the ionic liquids. The results show that our method provides a facile means that is complementary to X-ray crystallography, for obtaining structural information of ionic liquids.
authors.affiliation: Department of Applied Chemistry, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu, 30010, Taiwan.
authors.forename: Hong-Kai
authors.initials: HK
authors.lastname: Chen
authors.affiliation: Department of Chemistry, Banaras Hindu University, Varanasi, 221005, India.
authors.forename: Nitin
authors.initials: N
authors.lastname: Srivastava
authors.affiliation: Department of Chemistry, Banaras Hindu University, Varanasi, 221005, India.
authors.forename: Satyen
authors.initials: S
authors.lastname: Saha
authors.affiliation: Department of Applied Chemistry, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu, 30010, Taiwan. shigeto@kwansei.ac.jp.|Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, 669-1337, Japan. shigeto@kwansei.ac.jp.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Shigeto
keywords: ionic liquids; melting points; microheterogeneity; solid-state structures; vibrational spectroscopy