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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.

No MeSH data available.


Related in: MedlinePlus

Rietveld refinement fits at (a) 0.22 GPa and room temperature, (b) 1.09 GPa and room temperature and (c) 2 K and ambient pressure. The d-spacing ranges are 0.73-4.16 Å for (a) and (b) and 0.83 – 2.75 Å for (c).
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Fig1: Rietveld refinement fits at (a) 0.22 GPa and room temperature, (b) 1.09 GPa and room temperature and (c) 2 K and ambient pressure. The d-spacing ranges are 0.73-4.16 Å for (a) and (b) and 0.83 – 2.75 Å for (c).

Mentions: Rietveld refinements [20] were performed using TOPAS-Academic [21]. During refinement against the high-pressure data the piperidine molecules were treated as rigid groups using the Z-matrix formalism. Bond lengths and angles were taken from the previously determined structure (CSD refcode ITOBAU) [3] with deuterium distances set to standard neutron distances (N-H 1.009 Å, C-H 1.083 Å). Bond lengths, angles and torsion angles were not refined. All non-hydrogen atoms were refined with a common isotropic displacement parameter, as were all deuterium atoms. A fourth order spherical harmonic preferred orientation correction [22] was included as the sample was crystallised in situ. Ni and WC phases were also included in the refinement. The presence of these is due to the anvil cores of the Paris-Edinburgh press. Rietveld refinement profiles at 0.22 and 1.09 GPa are shown in Figure 1a and b, with crystal and refinement data given in Table 1. Peak broadening was quite pronounced above 1.09 GPa and detailed structure analysis was not carried out above this pressure.Figure 1


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

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

Rietveld refinement fits at (a) 0.22 GPa and room temperature, (b) 1.09 GPa and room temperature and (c) 2 K and ambient pressure. The d-spacing ranges are 0.73-4.16 Å for (a) and (b) and 0.83 – 2.75 Å for (c).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig1: Rietveld refinement fits at (a) 0.22 GPa and room temperature, (b) 1.09 GPa and room temperature and (c) 2 K and ambient pressure. The d-spacing ranges are 0.73-4.16 Å for (a) and (b) and 0.83 – 2.75 Å for (c).
Mentions: Rietveld refinements [20] were performed using TOPAS-Academic [21]. During refinement against the high-pressure data the piperidine molecules were treated as rigid groups using the Z-matrix formalism. Bond lengths and angles were taken from the previously determined structure (CSD refcode ITOBAU) [3] with deuterium distances set to standard neutron distances (N-H 1.009 Å, C-H 1.083 Å). Bond lengths, angles and torsion angles were not refined. All non-hydrogen atoms were refined with a common isotropic displacement parameter, as were all deuterium atoms. A fourth order spherical harmonic preferred orientation correction [22] was included as the sample was crystallised in situ. Ni and WC phases were also included in the refinement. The presence of these is due to the anvil cores of the Paris-Edinburgh press. Rietveld refinement profiles at 0.22 and 1.09 GPa are shown in Figure 1a and b, with crystal and refinement data given in Table 1. Peak broadening was quite pronounced above 1.09 GPa and detailed structure analysis was not carried out above this pressure.Figure 1

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