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

Mohaček-Grošev, Vlasta; Grdadolnik, Jože; Hadži, D.

doi:10.1021/acs.jpca.5b12577

Cited by 7 publications

(5 citation statements)

References 42 publications

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“…The BLF found in ADAD is not unique. A similar pattern is found in the spectra of oxalic acid dihydrate [ 7 , 8 , 14 ] and perfluorated fatty acid monohydrate [ 17 ]. Moreover, the BLFs in the spectra of the aforementioned compounds are also a complex structure of at least two components, which are similarly sensitive to temperature and/or deuterium exchange, as in the case of ADAD.…”

Section: Resultssupporting

confidence: 74%

“…The crystal and molecular structure of ADAD was determined 75 years ago through X-ray diffraction using photographic film detection [ 2 ] in the series of dicarboxylic acid hydrates such as diacetylenedicarboxylic acid [ 3 ] and oxalic acid dihydrates [ 4 , 5 ]. In contrast, crystals of the former compound were the subject of numerous X-ray and inelastic neutron scattering diffraction studies [ 6 ], and Raman [ 7 , 8 ] and infrared investigations [ 9 , 10 , 11 , 12 , 13 , 14 ], as well as molecular dynamics modelling [ 15 ] can give no indication of a corresponding interest in ADAD. The above crystals have a fairly similar structure, consisting of spiral chains with alternating strong hydrogen bonds between the hydroxyl groups of the acid and the water molecules, and weak hydrogen bonds between the water molecules and the carbonyl group of the acid molecules.…”

Section: Introductionmentioning

confidence: 99%

“…The O … O length of the shortest hydrogen bond is the same as in the crystal of oxalic acid dihydrate (OADH, 2.49 Å, at room temperature). Although the infrared spectra are very similar, especially the pattern that originates in the hydrogen bond network [ 7 , 14 , 17 ], the structure of the acid molecule is quite different, since PDFO formed a bilayer structure. The hydrogen bond pattern is centrosymmetric, with two water molecules and two carbonyl oxygen atoms forming a planar rhombic arrangement, with the water-hydrogen atoms almost within the plane.…”

Section: Introductionmentioning

confidence: 99%

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Strong Hydrogen Bonds in Acetylenedicarboxylic Acid Dihydrate

Novak

Golobič

Klančnik

et al. 2022

IJMS

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Acetylenedicarboxylic acid dihydrate (ADAD) represents a complex with strong hydrogen bonding between the carboxylic OH and the water molecule. An X-ray re-examination of the ADAD crystal structure confirms the O...O distance of the short hydrogen bonds, and clearly shows different bond lengths between the two oxygen atoms with respect to the carbon atom in the carboxyl group, indicating a neutral structure for the complex. The neutral structure was also confirmed by vibrational spectroscopy, as no proton transfer was observed. The diffraction studies also revealed two polymorph modifications: room temperature (α) and low temperature (β), with a phase transition at approximately 4.9 °C. The calculated vibrational spectra are in satisfactory agreement with the experimental spectra. A comparison of the structure and the vibrational spectra between the ADAD and the oxalic acid dihydrate reveals some interesting details. The crystal structures of both crystal hydrates are almost identical; only the O...O distances of the strongest hydrogen bonds differ by 0.08 Å. Although it was expected that a larger O...O spacing in the ADAD crystal may significantly change the infrared and Raman spectra, especially for the frequency and the shape of the acidic OH stretching vibration, both the shape and frequency are almost identical, with all subpeaks topped on the broad OH stretching vibration. The O…O distance dependent are only in- and out-of-plane OH deformations modes. The presence of polarons due to the ionized defects was not observed in the vibrational spectra of ADAD. Therefore, the origin of the broad OH band shape was explained in a similar way to the acid dimers. The anharmonicity of a potential enhances the coupling of the OH stretching with the low-frequency hydrogen bond stretching, which, in addition to the Fermi resonance, structures the band shape of the OH stretching. The fine structure found as a superposition of a broad OH stretching is attributed to Davydov coupling.

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Section: Resultssupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Strong Hydrogen Bonds in Acetylenedicarboxylic Acid Dihydrate

Novak

Golobič

Klančnik

et al. 2022

IJMS

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“…[16,17] The resemblance between PDFO·H2O and these systems extends to the infrared and Raman spectra that exhibit unique features related to proton dynamics. [18,19] This is also supported by ac conductivity measurements which give evidence for the polaronic character of conductivity. [20,21] Due to its sizable hydrophobic moiety, PDFO is a prototype for lipid membranes.…”

Section: Introductionmentioning

confidence: 53%

Structure Determination by Joint Effort of X-ray Powder Diffraction and Quantum Calculations: Crystal Structure and Short Hydrogen Bonding in Pentadecafluorooctanoic Acid Hydrate

Stare¹,

Meden²,

Hadži³

2018

Croat. Chem. Acta

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A precise X-ray crystal structure determination of systems that exist in a polycrystalline form often poses a challenge due to several factors that limit the resolution of the diffraction measurement. The location of atoms is usually determined at significantly lower precision than the unit cell parameters, rendering the complete characterization of the structure difficult. This is particularly pronounced when precise location of hydrogen atoms is required, for instance in ionizable biomolecules or in hydrogen bonds. In such cases periodic quantum (DFT) calculations may crucially assist structure determination, because they can reliably predict the location of atoms, provided that the unit cell parameters, the space group and tentative atomic positions are known. In this work we present DFT-assisted structure determination of pentadecafluorooctanoic acid hydrate, a benchmark system featuring short hydrogen bonds (RO...O ≈ 2.5 Å) between acid and water molecules. While Rietveld refinement based solely on powder diffraction data cannot reliably resolve the location of crystal water molecules and even less so the position of hydrogen atoms in the network of hydrogen bonds, periodic DFT optimization yields several minimum energy structures suitable for further refinement. Due to the low experimental resolution and similarity, comparison between model and experimental powder diffraction pattern can barely distinguish between certain structure candidates provided by DFT calculations, but it can rule out those featuring larger misfits. The proposed structure solution is delivered from a tandem application of structure determination from powder diffraction data and DFT optimization, the former providing the unit cell parameters and estimated atomic positions that are finely tuned by DFT. The present strategy can in principle be generalized to other examples of structure determination at relatively low resolution, such as is often the case with biological macromolecules.

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“…[34][35][36] This is reflected by similar features in the infrared spectra, 36) but more informative concerning proton transfer and polaron formation are the Raman spectra of oxalic acid dihydrate single crystals. 37) The effects of low temperature on protonic modes can be interpreted by proton transfer from the acid to water molecules and formation of small polarons in the hydrogen bonded spirals chains constituting the crystals. The polaron formation in KAP has not been observed in the Raman spectra since low temperatures were not reached.…”

Section: Resultsmentioning

confidence: 99%

Polaron conductivity mechanism in potassium acid phthalate crystal: AC-conductivity investigation

Filipič

Levstik

et al. 2016

Jpn. J. Appl. Phys.

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The complex dielectric constant, , of potassium acid phthalate monocrystal (KAP) was investigated over the broad frequency and temperature range. While the imaginary part of dielectric constant ε′′(ν) increases rapidly with increasing temperature in the studied temperature range, the real part of dielectric constant ε′(ν) increases only at high temperatures; there is almost no change of ε′(ν) below 200 K. Both values of ε′ and ε′′ are frequency dependent; the values increase with decreasing frequencies. At temperatures below 450 K the ac electrical conductivity and dielectric constant follow simultaneously the universal dielectric response (UDR). The analysis of the temperature dependence of the UDR parameter s in terms of the theoretical model for small polarons revealed that this mechanism governs the charge transport in KAP crystal in the studied temperature range.

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

Cited by 7 publications

References 42 publications

Strong Hydrogen Bonds in Acetylenedicarboxylic Acid Dihydrate

Strong Hydrogen Bonds in Acetylenedicarboxylic Acid Dihydrate

Structure Determination by Joint Effort of X-ray Powder Diffraction and Quantum Calculations: Crystal Structure and Short Hydrogen Bonding in Pentadecafluorooctanoic Acid Hydrate

Polaron conductivity mechanism in potassium acid phthalate crystal: AC-conductivity investigation

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