Proton-transfer dynamics in the hydrogen bond. Inelastic neutron scattering, infrared and Raman spectra of KH(CF3COO)2 and CsH(CF3COO)2

Tomkinson, J.

doi:10.1016/0301-0104(91)87059-5

Cited by 22 publications

(8 citation statements)

References 37 publications

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“…42 At room temperature, trifluoroacetate dimers, H͑CF 3 COO͒ 2 − , are linked by crystallographically symmetric hydrogen bonds with R OO = 2.435͑7͒ or 2.38͑3͒ Å, respectively. The vibrational spectra of these salts at a very low temperature 19,43,44 evidence several ͉x a ͘ n states in the same frequency range as for KHM ͑500-1100 cm −1 ͒ but with quite different profiles of intensity. In a previous work, 44 it was suggested that CTFA could be a LBHB case, but there is no neutron diffraction data to support this proposal.…”

Section: Introductionmentioning

confidence: 73%

“…The vibrational spectra of these salts at a very low temperature 19,43,44 evidence several ͉x a ͘ n states in the same frequency range as for KHM ͑500-1100 cm −1 ͒ but with quite different profiles of intensity. In a previous work, 44 it was suggested that CTFA could be a LBHB case, but there is no neutron diffraction data to support this proposal. We report below single crystal neutron diffraction measurements consistent with single wells for protons at any temperature.…”

Section: Introductionmentioning

confidence: 73%

“…The previously reported INS spectra of the two salts are very similar. 44 The ␥H modes give narrow single bands at Ϸ1225 cm −1 ͑KTFA͒ or Ϸ1260 cm −1 ͑CTFA͒ and overtones at Ϸ2450 cm −1 ͑KTFA͒ or Ϸ2515 cm −1 ͑CTFA͒, consistent with quasiharmonic oscillators. The intensity ratios I 0→2 / I 0→1 accord with an oscillator mass of Ϸ1 amu.…”

Section: Ins Band Profilesmentioning

confidence: 81%

“…For KTFA, the strong Raman bands at 850-854 cm −1 , analogous to those observed for CTFA, 44 suggest that the INS counterpart should exist, although it is not resolved.…”

Section: Ins Band Profilesmentioning

confidence: 92%

“…With the time focussed crystal analyzer ͑TFXA͒ spectrometer utilized in Ref. 44, only scattering events corresponding to the maximum of the scattering function for harmonic bare protons are counted ͑see Appendix͒. The previously reported INS spectra of the two salts are very similar.…”

Section: Ins Band Profilesmentioning

confidence: 93%

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A neutron scattering study of strong-symmetric hydrogen bonds in potassium and cesium hydrogen bistrifluoroacetates: Determination of the crystal structures and of the single-well potentials for protons

Cousson

Archilla

Tomkinson

2008

The Journal of Chemical Physics

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The crystal structures of potassium and cesium bistrifluoroacetates, KH͑CF 3 COO͒ 2 and CsH͑CF 3 COO͒ 2 , respectively, were determined at room and cryogenic temperatures with the single crystal neutron diffraction technique. The crystals belong to the monoclinic space groups, I2 / a and A2 / a, respectively, and there is no evidence of any structural phase transition. In both crystals, trifluoroacetate entities in centrosymmetric dimers are linked by very short hydrogen bonds lying across a center of inversion. The thermal parameters provide no evidence of any double minimum potential for hydrogen bond protons. Single-minimum potentials were determined via best fitting to the inelastic neutron scattering spectral profiles of the stretching vibrations. They comprise a narrow well for the ground state and a very broad quasiharmonic well for excited states. The spread out of the wave functions of these states shows that protons are no longer confined between the oxygens. Presumably, they are attracted by the lone pairs of oxygen atoms. These potentials emphasize the covalent nature of the OO bond and the ionic character of the hydrogen bond proton.

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Section: Introductionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 73%

Section: Ins Band Profilesmentioning

confidence: 81%

“…For KTFA, the strong Raman bands at 850-854 cm −1 , analogous to those observed for CTFA, 44 suggest that the INS counterpart should exist, although it is not resolved.…”

Section: Ins Band Profilesmentioning

confidence: 92%

Section: Ins Band Profilesmentioning

confidence: 93%

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