Characterization of urea single crystals

Rajalakshmi, T.; Fareed, R. S. Qhalid; Dhanasekaran, R.; Ramasamy, P.; Jacob, Thomas; Srinivasan, K.

doi:10.1016/0921-5107(95)01535-3

Cited by 21 publications

(9 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Both vibrations, however, are not pure but strongly coupled. The infrared absorptions at 1625 and 1466 cm -1 are assigned to the δ as (NH 2 ) and ν as (CN) vibrations, respectively, which is in total agreement with the literature. −,,,,,− , …”

Section: Vibrational Spectrum Of Ureasupporting

confidence: 87%

“…We assign the bands at 1625 and 1466 cm -1 to the δ as (NH 2 ) and to the ν as (CN) vibrations, respectively, which is in total agreement with the literature. −,,,,,− …”

Section: Vibrational Spectrum Of Ureasupporting

confidence: 86%

“…Stewart 76 observed two strong bands and one shoulder on the low-frequency side of the lowest band in the 3500−3000 cm -1 region of the infrared spectrum of urea, which he assigned to the NH 2 stretching vibrations. Other authors ,,− also observed these two bands and the shoulder but only assigned the two bands to the NH 2 stretching modes. Laulicht 48 explained the shoulder observed at about 3270 cm -1 as being a combination band of the symmetrical NH 2 -deformation and the CO-stretching vibration.…”

Section: Vibrational Spectrum Of Ureamentioning

confidence: 91%

See 2 more Smart Citations

Vibrational Analysis of Urea

Keuleers¹,

Desseyn²,

Rousseau³

et al. 1999

J. Phys. Chem. A

288

192

View full text Add to dashboard Cite

Although a lot of work has been done on the vibrational analysis of urea, there still remain some contradictions and uncertainties, mainly due to interpretation of the vibrational spectrum of crystalline urea based on force field calculations on isolated urea instead of on urea in its crystal phase. We have shown that this approach is not allowed in the case of urea. The vibrational spectrum of urea was interpreted by measuring the solid state infrared spectra of eight isotopomers of urea at room temperature and at −196 °C, and Raman spectra at room temperature and at −120 °C, and of a urea−water solution. Force field calculations from our recently published article on isolated urea and on urea in its crystal structure, at the Hartree−Fock level with a 6-31++G** basis set, were also used. We have also shown that high-pressure measurements using a “diamond anvil cell” are not useful by performing a vibrational analysis.

show abstract

Section: Vibrational Spectrum Of Ureasupporting

confidence: 87%

“…We assign the bands at 1625 and 1466 cm -1 to the δ as (NH 2 ) and to the ν as (CN) vibrations, respectively, which is in total agreement with the literature. −,,,,,− …”

Section: Vibrational Spectrum Of Ureasupporting

confidence: 86%

Section: Vibrational Spectrum Of Ureamentioning

confidence: 91%

See 1 more Smart Citation

Vibrational Analysis of Urea

Keuleers¹,

Desseyn²,

Rousseau³

et al. 1999

J. Phys. Chem. A

288

192

View full text Add to dashboard Cite

show abstract

“…In part these problems originated from the fact that the interpretation of its solid-state spectrum was based on gas-phase calculations. For example some authors − have assigned the band at 1683 cm -1 in the solid-state vibrational spectrum of urea to the C−O stretching vibration and the band at 1598 cm -1 to the symmetric NH 2 deformation mode, whereas others − assigned them in reversed order. It will be shown that, on the basis of experimental and calculated data, the latter is the more likely.…”

Section: Introductionmentioning

confidence: 99%

Solids Modeled by Ab-Initio Crystal Field Methods. Part 17. Study of the Structure and Vibrational Spectrum of Urea in the Gas Phase and in Its P4̄2₁m Crystal Phase

Rousseau¹,

Alsenoy²,

Keuleers³

et al. 1998

J. Phys. Chem. A

View full text Add to dashboard Cite

In this study the geometrical structure and vibrational spectrum are studied for the urea molecule (CO(NH2)2) in the gas phase as well as in its P4̄21 m crystal phase. Experimental frequencies for urea in the crystal phase are determined for the CO(NH2)2, C18O(NH2)2, CO(15NH2)2, 13CO(NH2)2, CO(ND2)2, C18O(ND2)2, CO(15ND2)2, and 13CO(ND2)2 isotopomers. Using calculations at the RHF/6-31++G** level, the equilibrium geometry and harmonic force field for both the gas phase and the crystal phase are determined. The crystal phase is modeled using a 15 molecule cluster surrounded by 5312 point charges. Calculated structure and frequencies are in excellent agreement with experiment. Shifts in frequencies for the above-mentioned isotopomers are reproduced with a root mean square deviation and largest difference of 15 and 43 cm-1, respectively. Shifts in frequencies in going from the gas phase to the crystal phase for the parent and deuterated isotopomer are reproduced with a root mean square deviation and largest difference of 14 and 31 cm-1, respectively.

show abstract

“…Indeed, fragments of this derivative were found when analyzing bulk samples of [C 2 C 1 Im][OTf] that were treated with ozone by direct analysis in real time mass spectrometry (DART‐MS). The additional weak feature at 1470 cm –1 seen in the IR spectrum may indeed be indicative for a ν as (N–C–N) unit . Theoretical and experimental work shows that the C–N stretching vibration of urazoles calculated are located in this range, and the same holds for compound 1 , biuret, which shows a band between 1476 cm –1 and 1490 cm –1 .…”

Section: Discussionmentioning

confidence: 99%

ZnO Nanoparticle Formation from the Molecular Precursor [MeZnOtBu]₄ by Ozone Treatment in Ionic Liquids: in‐situ Vibrational Spectroscopy in an Ultrahigh Vacuum Environment

Bauer

Voggenreiter

et al. 2016

Zeitschrift anorg allge chemie

View full text Add to dashboard Cite

As reported previously, novel ZnO nanostructures can be grown by oxidation of [MeZnOtBu]4 “building blocks” with O3 in ionic liquids (ILs). In this study, we have explored the role of the IL during ZnO formation by in‐situ infrared reflection absorption spectroscopy (IRAS) in ultrahigh vacuum (UHV). [MeZnOtBu]4 and [C2C1Im][OTf] were (co‐)deposited as thin films by physical vapor deposition (PVD) onto Au(111), separately or simultaneously. The IR spectrum of [MeZnOtBu]4 was analyzed between 300 and 4000 cm–1 based on calculated spectra from density‐functional theory (DFT). Spectral changes in the IL‐related bands during the thermal treatment of [MeZnOtBu]4 in [C2C1Im][OTf] indicate the loss of the precursor ligands and the interaction of the IL with the growing ZnO aggregates. The films were treated with ozone (10–6 mbar) in UHV and the spectral changes were monitored in‐situ by IRAS. Slow ozonolysis of [C2C1Im][OTf] is observed. Spectroscopically we identify the primary ozonide formed by addition of O3 to [C2C1Im]+ and suggest a reaction mechanism, which leads to a biuret derivative. Upon ozone treatment of mixed [MeZnOtBu]4/[C2C1Im][OTf] films, ZnO aggregates are formed at the IL/vacuum interface. Ozonolysis of [C2C1Im][OTf] is suppressed. Upon annealing to 320 K, further ZnO aggregates are formed, leading to enclosure of [C2C1Im][OTf] in the ZnO film. At 380 K the IL is released from the mixed film. The pure [C2C1Im][OTf] desorbs at 420 K, leaving behind the ZnO phase.

show abstract

Characterization of urea single crystals

Cited by 21 publications

References 9 publications

Vibrational Analysis of Urea

Vibrational Analysis of Urea

Solids Modeled by Ab-Initio Crystal Field Methods. Part 17. Study of the Structure and Vibrational Spectrum of Urea in the Gas Phase and in Its P4̄2₁m Crystal Phase

ZnO Nanoparticle Formation from the Molecular Precursor [MeZnOtBu]₄ by Ozone Treatment in Ionic Liquids: in‐situ Vibrational Spectroscopy in an Ultrahigh Vacuum Environment

Contact Info

Product

Resources

About

Characterization of urea single crystals

Cited by 21 publications

References 9 publications

Vibrational Analysis of Urea

Vibrational Analysis of Urea

Solids Modeled by Ab-Initio Crystal Field Methods. Part 17. Study of the Structure and Vibrational Spectrum of Urea in the Gas Phase and in Its P4̄21m Crystal Phase

ZnO Nanoparticle Formation from the Molecular Precursor [MeZnOtBu]4 by Ozone Treatment in Ionic Liquids: in‐situ Vibrational Spectroscopy in an Ultrahigh Vacuum Environment

Contact Info

Product

Resources

About

Solids Modeled by Ab-Initio Crystal Field Methods. Part 17. Study of the Structure and Vibrational Spectrum of Urea in the Gas Phase and in Its P4̄2₁m Crystal Phase

ZnO Nanoparticle Formation from the Molecular Precursor [MeZnOtBu]₄ by Ozone Treatment in Ionic Liquids: in‐situ Vibrational Spectroscopy in an Ultrahigh Vacuum Environment