Diffusion Ordered Spectroscopy of Room Temperature Chloroaluminate Melts

Larive, Cynthia K.; Lin, Mengfen; Piersma, Bernard J.; Carper, W. Robert

doi:10.1021/j100033a008

Cited by 33 publications

(68 citation statements)

References 8 publications

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“…The There is evidence of hydrogen bonding from NMR, IR and conductimetric studies between 1-alkyl-3-methylimidazolium cations and the halides, and there is indirect evidence of hydrogen bonding between 1-alkyl-3-methylimidazolium cations and BF 4 (Fig. 1) has five H-F distances that are shorter than the van der Waals H-F distance of 2.67Å.…”

Section: Molecular Structuresmentioning

confidence: 97%

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Evidence for spin diffusion in a H,H‐NOESY study of imidazolium tetrafluoroborate ionic liquids

Heimer

Sesto

Carper

2003

Magnetic Reson in Chemistry

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The ionic liquids 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) and 1-methyl-3-propylimidazolium tetrafluoroborate ([PMIM][BF4]) were studied by H,H-NOESY NMR using a cross-relaxation matrix analysis. Cross-peak intensities are seen to increase with increasing mixing time. Experimental and theoretical hydrogen-hydrogen distances are in agreement at short mixing times (50 ms). Mixing times longer than 50 ms result in an increasing contribution of spin diffusion that produces unrealistically short hydrogen-hydrogen distances. Gas-phase ab initio molecular structures are obtained using Hartree-Fock (HF) and density functional theory (B3LYP) methods at the 6311 + G(2d,p) basis set level. The hydrogen-hydrogen distances obtained from the theoretical structures are in reasonable agreement with those calculated from the cross-relaxation matrices.

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Section: Molecular Structuresmentioning

confidence: 97%

“…2. In the latter case, a ring methyl hydrogen, H16, the ring C2-H (H4) and hydrogens in the methylene groups, H12 and H18, form H-F hydrogen bonds with BF 4 The peak volume integrals at any mixing time, A m , are given by the equation…”

Section: Molecular Structuresmentioning

confidence: 99%

Evidence for spin diffusion in a H,H‐NOESY study of imidazolium tetrafluoroborate ionic liquids

Heimer

Sesto

Carper

2003

Magnetic Reson in Chemistry

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“…Early studies probed the nature of interactions in socalled first-generation chloroaluminate ionic liquids [40], and now also information becomes available for second generation, air-stable systems, such as the imidazolium mixtures. Many RTIL studies have been directed towards possible applications [8, 11, 41]: a number of reports have been published covering theoretical aspects [42][43][44][45][46][47], X-ray crystallography of the frozen melts [48][49][50][51][52], NMR relaxation, conductivity, viscosity, diffusion [4,28,[53][54][55][56][57][58][59], and gas solubilities in ionic liquids [22,60]. Hydrogen-bonding is known to occur between the cations and anions in most ionic liquids, as demonstrated by several investigators on e.g., systems containing 1-alkyl-3-methylimidazolium.…”

Section: N]mentioning

confidence: 99%

Raman Spectroscopy and Ab-Initio Model Calculations on Ionic Liquids

2007

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Summary.A review of the recent developments in the study and understanding of room temperature ionic liquids are given. An intimate picture of how and why these liquids are not crystals at ambient conditions is attempted, based on evidence from crystallographical results combined with vibrational spectroscopy and ab-initio molecular orbital calculations. A discussion is given, based mainly on some recent FT-Raman spectroscopic results on the model ionic liquid system of 1-butyl-3-methylimidazolium ([C 4 mim][X]) salts. The rotational isomerism of the [C 4 mim] þ cation is described: the presence of anti and gauche conformers that has been elucidated in remarkable papers by Hamaguchi et al. Such presence of a conformational equilibrium seems to be a general feature of the room temperature liquids. Then the ''localized structure features'' that apparently exist in ionic liquids are described. It is hoped that the structural resolving power of Raman spectroscopy will be appreciated by the reader. It is of remarkable use on crystals of known different conformations and on the corresponding liquids, especially in combination with modern quantum mechanics calculations. It is hoped that these interdisciplinary methods will be applied to many more systems in the future. A few examples will be discussed.

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“…The nuclear Overhauser (NOE) factor η i of carbon atom i relaxed by N H protons j is given by [9,10,11,12,13,14,15]: (2) where Σ includes from j=1 to N H , σ ij is the cross-relaxation rate, ρ ij is the dipolar relaxation rate, and the leakage term that represents the contribution of all other relaxation mechanisms to the relaxation of a 13 C nucleus i, thus reducing the NOE factor. Usually, intermolecular dipolar contributions can be neglected for 13 C nuclei with directly bonded protons.…”

Section: Nuclear Overhauser Effectmentioning

confidence: 99%

“…This is unfortunate, as NMR relaxation studies can often provide considerable information about phase changes, changes in molecular conformation and the ability of molecules to undergo reorientational molecular dynamics as a function of temperature [1]. Such information can be correlated with NMR (2D) NOESY studies and theoretical studies at the semi-empirical and ab-initio levels to provide details of liquid-state molecular structure [2,3,4].…”

Section: Introductionmentioning

confidence: 99%

A Bloembergen?Purcell?Pound 13 C NMR relaxation study of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate

Carper

Wahlbeck

Antony

et al. 2004

Analytical and Bioanalytical Chemistry

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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.

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Diffusion Ordered Spectroscopy of Room Temperature Chloroaluminate Melts

Cited by 33 publications

References 8 publications

Evidence for spin diffusion in a H,H‐NOESY study of imidazolium tetrafluoroborate ionic liquids

Evidence for spin diffusion in a H,H‐NOESY study of imidazolium tetrafluoroborate ionic liquids

Raman Spectroscopy and Ab-Initio Model Calculations on Ionic Liquids

A Bloembergen?Purcell?Pound 13 C NMR relaxation study of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate

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