A Bloembergen-Purcell-Pound 13C NMR relaxation study of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate.
The molecular structure and rotational motion of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) were studied over a wide temperature range using the Bloembergen-Purcell-Pound 13C NMR spin-lattice relaxation method and NOE factors. Examination of the spin-lattice relaxation times (T1) and the rates (R1 = 1/T1) of the 1-butyl-3-methylimidazolium cation reveals the relative motions of each carbon in the imidazolium cation. The rotational characteristics of the [BMIM] cation are supported by ab-initio molecular structures of [BMIM][PF6] using density functional theory (DFT) and Hartree-Fock (HF) methods. The ab-initio gas phase structures of [BMIM][PF6] indicate that the 1-butyl-3-methylimidazolium C2 hydrogen, the ring methyl group, and the butyl side-chain hydrogen atoms form hydrogen bonds with the hexafluorophosphate anion.
Carper
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Department of Chemistry, Wichita State University, Wichita, Kansas 67260-0051, USA. Bob.Carper@wichita.edu
Wahlbeck
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Antony
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Mertens
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Dölle
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Wasserscheid
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