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The effect of temperature and pressure on the crystal structure of piperidine.

Budd LE, Ibberson RM, Marshall WG, Parsons S - Chem Cent J (2015)

Bottom Line: Analysis of the thermal expansion data in the light of phonon frequencies determined in periodic DFT calculations indicates that the expansion at very low temperature is governed by external lattice modes, but above 100 K the influence of intramolecular ring-flexing modes also becomes significant.The principal directions of thermal expansion are determined by the sensitivity of different van der Waals interactions to changes in distance.The principal values of the strain developed on application of pressure are similarly oriented to those determined in the variable-temperature study, but more isotropic because of the need to minimise volume by filling interstitial voids at elevated pressure.

View Article: PubMed Central - PubMed

Affiliation: EaStCHEM School of Chemistry and Centre for Science at Extreme Conditions, The University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, EH9 3FJ UK.

ABSTRACT

Background: The response of molecular crystal structures to changes in externally applied conditions such as temperature and pressure are the result of a complex balance between strong intramolecular bonding, medium strength intermolecular interactions such as hydrogen bonds, and weaker intermolecular van der Waals contacts. At high pressure the additional thermodynamic requirement to fill space efficiently becomes increasingly important.

Results: The crystal structure of piperidine-d11 has been determined at 2 K and at room temperature at pressures between 0.22 and 1.09 GPa. Unit cell dimensions have been determined between 2 and 255 K, and at pressures up to 2.77 GPa at room temperature. All measurements were made using neutron powder diffraction. The crystal structure features chains of molecules formed by NH…N H-bonds with van der Waals interactions between the chains. Although the H-bonds are the strongest intermolecular contacts, the majority of the sublimation enthalpy may be ascribed to weaker but more numerous van der Waals interactions.

Conclusions: Analysis of the thermal expansion data in the light of phonon frequencies determined in periodic DFT calculations indicates that the expansion at very low temperature is governed by external lattice modes, but above 100 K the influence of intramolecular ring-flexing modes also becomes significant. The principal directions of thermal expansion are determined by the sensitivity of different van der Waals interactions to changes in distance. The principal values of the strain developed on application of pressure are similarly oriented to those determined in the variable-temperature study, but more isotropic because of the need to minimise volume by filling interstitial voids at elevated pressure. Graphical AbstractThough H-bonds are important interactions in the crystal structure of piperidine, the response to externally-applied conditions are determined by van der Waals interactions.

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Interstitial voids at (a) 0.22 and (b) 1.09 GPa. Images were generated using the experimentally determined coordinates; a movie extended to 2.77 GPa using the DFT optimised coordinates is available in the Additional file 3: Movie S2b).
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Fig10: Interstitial voids at (a) 0.22 and (b) 1.09 GPa. Images were generated using the experimentally determined coordinates; a movie extended to 2.77 GPa using the DFT optimised coordinates is available in the Additional file 3: Movie S2b).

Mentions: A movie showing the effect of pressure, generated using optimised structures in the same way as the movie for temperature described above in “The effect of temperature on the structure of piperidine”, is available in the Additional file 3: Movie S2a). Comparison of the pressure and temperature series movies shows the more nearly isotropic distribution of strain as well as more prominent changes in the orientations of the molecules under compression. The largest interatomic distance change occurs for C5H10…H3, which measures 3.04 Å at 0.22 GPa and 2.51 Å at 1.09 GPa, a reduction of 17.4%. Other contacts listed in Table 2 change by between 4 and 8%; the hydrogen bonds shorten from 2.18 Å at 0.22 GPa to 2.09 Å at 1.09 GPa. The overall effect is to fill the rather large interstitial voids formed between the H-bonded chains (Figure 10, Additional file 3: Movie S2b).Figure 10


The effect of temperature and pressure on the crystal structure of piperidine.

Budd LE, Ibberson RM, Marshall WG, Parsons S - Chem Cent J (2015)

Interstitial voids at (a) 0.22 and (b) 1.09 GPa. Images were generated using the experimentally determined coordinates; a movie extended to 2.77 GPa using the DFT optimised coordinates is available in the Additional file 3: Movie S2b).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4403828&req=5

Fig10: Interstitial voids at (a) 0.22 and (b) 1.09 GPa. Images were generated using the experimentally determined coordinates; a movie extended to 2.77 GPa using the DFT optimised coordinates is available in the Additional file 3: Movie S2b).
Mentions: A movie showing the effect of pressure, generated using optimised structures in the same way as the movie for temperature described above in “The effect of temperature on the structure of piperidine”, is available in the Additional file 3: Movie S2a). Comparison of the pressure and temperature series movies shows the more nearly isotropic distribution of strain as well as more prominent changes in the orientations of the molecules under compression. The largest interatomic distance change occurs for C5H10…H3, which measures 3.04 Å at 0.22 GPa and 2.51 Å at 1.09 GPa, a reduction of 17.4%. Other contacts listed in Table 2 change by between 4 and 8%; the hydrogen bonds shorten from 2.18 Å at 0.22 GPa to 2.09 Å at 1.09 GPa. The overall effect is to fill the rather large interstitial voids formed between the H-bonded chains (Figure 10, Additional file 3: Movie S2b).Figure 10

Bottom Line: Analysis of the thermal expansion data in the light of phonon frequencies determined in periodic DFT calculations indicates that the expansion at very low temperature is governed by external lattice modes, but above 100 K the influence of intramolecular ring-flexing modes also becomes significant.The principal directions of thermal expansion are determined by the sensitivity of different van der Waals interactions to changes in distance.The principal values of the strain developed on application of pressure are similarly oriented to those determined in the variable-temperature study, but more isotropic because of the need to minimise volume by filling interstitial voids at elevated pressure.

View Article: PubMed Central - PubMed

Affiliation: EaStCHEM School of Chemistry and Centre for Science at Extreme Conditions, The University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, EH9 3FJ UK.

ABSTRACT

Background: The response of molecular crystal structures to changes in externally applied conditions such as temperature and pressure are the result of a complex balance between strong intramolecular bonding, medium strength intermolecular interactions such as hydrogen bonds, and weaker intermolecular van der Waals contacts. At high pressure the additional thermodynamic requirement to fill space efficiently becomes increasingly important.

Results: The crystal structure of piperidine-d11 has been determined at 2 K and at room temperature at pressures between 0.22 and 1.09 GPa. Unit cell dimensions have been determined between 2 and 255 K, and at pressures up to 2.77 GPa at room temperature. All measurements were made using neutron powder diffraction. The crystal structure features chains of molecules formed by NH…N H-bonds with van der Waals interactions between the chains. Although the H-bonds are the strongest intermolecular contacts, the majority of the sublimation enthalpy may be ascribed to weaker but more numerous van der Waals interactions.

Conclusions: Analysis of the thermal expansion data in the light of phonon frequencies determined in periodic DFT calculations indicates that the expansion at very low temperature is governed by external lattice modes, but above 100 K the influence of intramolecular ring-flexing modes also becomes significant. The principal directions of thermal expansion are determined by the sensitivity of different van der Waals interactions to changes in distance. The principal values of the strain developed on application of pressure are similarly oriented to those determined in the variable-temperature study, but more isotropic because of the need to minimise volume by filling interstitial voids at elevated pressure. Graphical AbstractThough H-bonds are important interactions in the crystal structure of piperidine, the response to externally-applied conditions are determined by van der Waals interactions.

No MeSH data available.


Related in: MedlinePlus