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dc.contributor.authorShukla, Madhulataen_US
dc.contributor.authorNoothalapati, Hemanthen_US
dc.contributor.authorShigeto, Shinsukeen_US
dc.contributor.authorSaha, Satyenen_US
dc.date.accessioned2015-07-21T11:20:33Z-
dc.date.available2015-07-21T11:20:33Z-
dc.date.issued2014-11-01en_US
dc.identifier.issn0924-2031en_US
dc.identifier.urihttp://dx.doi.org/10.1016/j.vibspec.2014.10.006en_US
dc.identifier.urihttp://hdl.handle.net/11536/124129-
dc.description.abstractPiperidinium cation-based room temperature ionic liquids (RTILs) constitute an important class of ILs because of their unique electrochemical properties as well as non-aromatic nature of the cation. However, detailed structural studies are yet to be done. In this paper, we discuss the molecular structure and vibrational spectra of N-butyl-N-methylpiperidinium bis(trifluromethanesulfonyl) imide, (PIP14NTf2; where, PIP14 is N-butyl-N-methylpiperidinium and NTf2 is bis(trifluromethanesulfonyl) imide), obtained with a combined approach of infrared (IR) and Raman spectroscopies in the liquid state and density functional theory (DFT) and Hartree-Fock (H-F) based theoretical calculations. DFT calculations, which are found to produce the most stable geometry compared to other two methods (MP2 and H-F), reproduce the experimental IR and Raman spectra reasonably well. Our findings reveal structural properties that profoundly influence intermolecular interactions and melting point. There exists a large variation in the melting point of the ILs studied. While the bromide salt of the piperidinium derivative (PIP14Br) is solid with very high melting point (241 degrees C), the corresponding NTf2 salt is low viscous liquid at room temperature (mp: -25 degrees C). bmimBr (bmim = 1-butyl-1-methylimidazolium) exhibits a substantially lower melting point of 79 degrees C than PIP14Br, suggesting that more number of strong classical hydrogen bonding interactions in the latter is primarily responsible for the much higher melting point. In addition, involvement of the alkyl group in PIP14 in H-bonding interaction provides additional rigidity in n-butyl chain which is otherwise absent in bmimBr. Interaction energy for PIP14Br is found to be higher than PIP14NTf2, showing a positive correlation between interaction energy and melting point. A blue shift in C-H stretching wavenumber as evident from IR and Raman spectra of PIP14Br IL is a clear indication of the stronger hydrogen bonding as compared to PIP14NTf2 IL. Furthermore, we experimentally observe the existence of cisoid-transoid conformational equilibrium of NTf2- anion in the Raman spectrum of PIP14NTf2 for the first time and determined that transoid NTf2- anion to be more stable than the corresponding cisoid conformer by 1.04 kcal/mol using DFT. Examination of various conformational possibilities of the cation shows that the butyl group preferentially exists in gauche conformation. (C) 2014 Elsevier B.V. All rights reserved.en_US
dc.language.isoen_USen_US
dc.subjectIonic liquiden_US
dc.subjectPiperidinium cationen_US
dc.subjectBis(trifluoromethanesulfonyl)imide anionen_US
dc.subjectRaman spectroscopyen_US
dc.subjectVibrational modesen_US
dc.subjectH-bonding interactionen_US
dc.subjectInteraction energyen_US
dc.subjectDensity functional theoryen_US
dc.titleImportance of weak interactions and conformational equilibrium in N-butyl-N-methylpiperidinium bis(trifluromethanesulfonyl) imide room temperature ionic liquids: Vibrational and theoretical studiesen_US
dc.typeArticleen_US
dc.identifier.doi10.1016/j.vibspec.2014.10.006en_US
dc.identifier.journalVIBRATIONAL SPECTROSCOPYen_US
dc.citation.volume75en_US
dc.citation.spage107en_US
dc.citation.epage117en_US
dc.contributor.department應用化學系zh_TW
dc.contributor.department應用化學系分子科學碩博班zh_TW
dc.contributor.departmentDepartment of Applied Chemistryen_US
dc.contributor.departmentInstitute of Molecular scienceen_US
dc.identifier.wosnumberWOS:000347022400014en_US
dc.citation.woscount0en_US
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