Spectres d'absorption de l'acide oxalique dihydraté dans l'infrarouge lointain

Wyncke, B.; Bréhat, F.; Hadni, A.

doi:10.1051/jphys:01975003609087700

Cited by 3 publications

(12 citation statements)

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“…De Villepin and Novak [12] concentrated on the isotope effects on the stretching modes of the short and long H-bonds. Wyncke et al [13] analyzed the far infrared (IR) spectra of OADH. To the best of our knowledge, no complete analysis of single-crystal Raman spectra of OADH has been published.…”

Section: Introductionmentioning

confidence: 99%

Identification of hydrogen bond modes in polarized Raman spectra of single crystals of α‐oxalic acid dihydrate

Mohaček-Grošev

Grdadolnik

Stare

et al. 2009

J Raman Spectroscopy

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Polarized Raman spectra of single crystals of the α-polymorphs of protonated and deuterated oxalic acid dihydrate were recorded. The interpretation of the spectra is assisted by periodic DFT calculations using the CRYSTAL06 program and by comparison with the infrared spectra of the polycrystalline material. The agreement between the calculated and observed band wavenumbers is fair in the case of low-anharmonicity modes, but marked differences appear for the stretching modes that are strongly anharmonic. A very broad feature, extending between ∼2000 and 1200 cm −1 , is attributed to OH stretching. Notable is the topping of this feature by distinct bands that can be attributed to C O stretching, H 2 O scissoring and COH bending coupled to C-O stretching. The assignments are supported by isotope effects. However, deuteration does not notably affect the wavenumber limits of the broad OH stretching band, which suggests that the potential governing the proton dynamics is of the asymmetric double-minimum type with a very low barrier. The calculated normal coordinates show a strong participation of the bending modes of water molecules in almost all internal acid motions, as well as in the external phonons.

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Section: Introductionmentioning

confidence: 99%

Identification of hydrogen bond modes in polarized Raman spectra of single crystals of α‐oxalic acid dihydrate

Mohaček-Grošev

Grdadolnik

Stare

et al. 2009

J Raman Spectroscopy

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“…Low frequency Raman spectra of OXAC dihydrate are completely in accord with the existence of a single stable phase (Figure 2). However, Wyncke et al observed an infrared phonon at 44.5 cm −1 at 300 K when the electric field was parallel to a, whose position shifted to 46.5 cm −1 at 223 K and did not shift further on cooling, but whose intensity steadily ceased and which vanished at 80 K. 13 We point out that temperature dependent Raman spectra in the interval from 1000 to 2000 cm −1 require particular attention because the changes observed are quite remarkable. Figure 3 displays Raman spectra of powder and Figure 4 y(zz)x polarized Raman spectrum of a single crystal of protonated oxalic acid dihydrate (OXAC).…”

Section: ■ Results and Discussionmentioning

confidence: 98%

“…However, Wyncke et al observed an infrared phonon at 44.5 cm -1 at 300 K when electric field was parallel to a, whose position shifted to 46.5 cm -1 at 223 K and did not shift further on cooling, but whose intensity steadily ceased and which vanished at 80 K 13 .…”

Section: Resultsmentioning

confidence: 98%

“…Early vibrational spectroscopic 4 studies by Villepin and Novak [10][11][12] and single crystal far infrared study by Wyncke et al 13 attracted many other researchers to tackle the dynamics of this crystal using deuteron NMR 14 , ac conductivity measurements 15 , Raman 16,17 , high pressure X-ray 18 and neutron diffraction 19 , teraherz spectroscopy accompanied with density functional theory calculation 20 and Car-Parrinello molecular dynamics simulation 21 .…”

Section: Introductionmentioning

confidence: 99%

“…Oxalic acid (OXAC) dihydrate is an exemplary system displaying strong hydrogen bonding, examined repeatedly by X-ray and neutron diffraction. − Early vibrational spectroscopic studies by de Villepin and Novak − and single crystal far-infrared study by Wyncke et al attracted many other researchers to tackle the dynamics of this crystal using deuteron NMR, ac conductivity measurements, Raman, , high pressure X-ray and neutron diffraction, teraherz spectroscopy accompanied by density functional theory calculation, and Car–Parrinello molecular dynamics simulation …”

Section: Introductionmentioning

confidence: 99%

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Evidence of Polaron Excitations in Low Temperature Raman Spectra of Oxalic Acid Dihydrate

2016

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Low temperature Raman spectra of oxalic acid dihydrate (8K -300 K) both for polycrystalline and single crystal phase show strong variation with temperature in the interval from 1200 to 2000 cm -1 . Previous low temperature diffraction studies all confirmed the stability of the crystal P21/n phase with no indications of any phase transition, reporting the existence of a strong hydrogen bond between the oxalic acid and a water molecule. A new group of Raman bands in the 1200 -1300 cm -1 interval below 90 K is observed, caused by possible loss of the centre of inversion.This in turn could originate either due to disorder in hydroxyl proton positions, or due to proton transfer from carboxylic group to water molecule. The hypothesis of proton transfer is further supported by the emergence of new bands centered at 1600 cm -1 and 1813 cm -1 , which can be explained with vibrations of H3O + ions. The broad band at 1600 cm -1 looses intensity, while the band at 1813 cm -1 gains intensity on cooling. The agreement between quantum calculations of vibrational spectra and experimentally observed Raman bands of hydronium ions in oxalic acid sesquihydrate crystal corroborate this hypothesis.

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Effect of Waters of Crystallization on Terahertz Spectra: Anhydrous Oxalic Acid and Its Dihydrate

King

Korter

2010

J. Phys. Chem. A

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Oxalic acid and oxalic acid dihydrate were studied using terahertz spectroscopy and solid-state density functional theory (DFT) in the spectral range 10-100 cm(-1). The size of the oxalic acid molecule and its limited internal degrees of freedom make it ideal for evaluating the performance of computational methods for the structural and dynamical simulation of strongly hydrogen-bonded solids. Calculations of the solid-state structures and terahertz spectra of oxalic acid and oxalic acid dihydrate were performed using the hybrid B3LYP and B3PW91 and the nonhybrid BLYP and PW91 density functionals employing the 6-311G(2d,2p) basis set. When these simulations were compared to the experimental spectra of the oxalic acid solids, a constant overprediction of the dihydrate frequencies was observed in contrast to the results of the anhydrous system. This change in behavior is connected to the nature of the vibrational motions being accessed. The primary molecular motion contributions to the terahertz vibrations of oxalic acid dihydrate were found to originate in the external motions of the cocrystallized H(2)O molecules. The observed overestimation of the vibrational energies in the simulated terahertz spectra is attributed to increased anharmonicity of the vibrational motions in the dihydrate system versus the anhydrous, resulting from weaker hydrogen bonding through the networked water molecules.

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Spectres d'absorption de l'acide oxalique dihydraté dans l'infrarouge lointain

Cited by 3 publications

References 6 publications

Identification of hydrogen bond modes in polarized Raman spectra of single crystals of α‐oxalic acid dihydrate

Identification of hydrogen bond modes in polarized Raman spectra of single crystals of α‐oxalic acid dihydrate

Evidence of Polaron Excitations in Low Temperature Raman Spectra of Oxalic Acid Dihydrate

Effect of Waters of Crystallization on Terahertz Spectra: Anhydrous Oxalic Acid and Its Dihydrate

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