A study of the conformers of the N,N-diethyl-N-methyl-N-propylammonium ion by means of infrared spectroscopy and DFT calculations |
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| Institution: | 1. CNR-ISC, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Roma, Italy;2. Physics Department, Sapienza University of Rome, Piazzale A. Moro 5, 00185 Roma, Italy;1. Department of Chemistry, Wesleyan University, Hall-Atwater Laboratories, 52 Lawn Ave, Middletown, CT 06459, United States;2. Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99354, United States;3. School of Natural and Social Sciences, Purchase College SUNY, 735 Anderson Hill Rd, Purchase, NY 10577, United States;1. Alberta Innovates – Technology Futures, 250 Karl Clark Road, Edmonton, Alberta T6E 6&4, Canada;2. Computer Modelling Group Ltd., Calgary, Alberta T2L 2A6, Canada;3. Alberta Innovates – Technology Futures, Edmonton, Alberta T6N 1E4, Canada;1. Dept. of Chemistry, University of Rome “La Sapienza”, p.le Aldo Moro 5, 00185 Rome, Italy;2. Centre for Hybrid and Organic Solar Energy (CHOSE), Dept. of Electronic Engineering, University of Rome “Tor Vergata”, via del Politecnico 1, 00133 Rome, Italy;3. Dept. of Chemical Sciences, University of Naples “Federico II”, Complesso Universitario Monte Sant’Angelo, 80126, Via Cintia, Naples, Italy;1. Department of Chemistry, South Ural State University, Russia;2. Department of Quantum Chemistry, D.I. Mendeleev University of Chemical Technology, Russia |
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| Abstract: | The infrared absorption spectrum of the N,N-diethyl-N-methyl-N-propylammonium (DMPA) bis(fluorosulfonyl)imide (FSI) ionic liquid is measured as a function of temperature between 165 and 307 K. In the frequency range between 900 and 1070 cm−1 only the cation gives rise to infrared bands. A conformational analysis of DMPA is performed by means of DFT calculations at the B3LYP/6-31G** level. The comparison of the experimental and calculated spectra provides evidence that the lowest energy conformers coexist in the liquid. Experimentally, we find that the energy difference between the most stable rotamer and the next energy conformers is only 1.56 ± 0.05 kJ/mol, in good agreement with the calculated value. Finally, we show that in the solid state only the most stable isomer is retained. |
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| Keywords: | Infrared spectra Ionic liquids DFT calculations Dynamic mechanical analysis Phase transitions Ammonium |
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