The structure of anthracene-d10 at 16 K using neutron diffraction

Abstract

The crystal structure of anthracene-d~0 at 16 K has been refined using neutron diffraction measurements [Cl4Dlo, P2~/a, a = 8.37 (3), b = 6.00(2), c = 11.12 (4)/k, fl = 125.4 (1) ° ]. Using 1105 structure factors, an R factor of 6.0% was obtained, which reduced to 3.2% when a simple one-parameter correction was made for multiple Bragg scattering, although this correction is not correlated to the crystal structure result. Constrained refinements have also been carried out which indicate significant distortions in the crystalline state from the free-molecule symmetry of mmm.The thermal-parameter analysis shows that the T tensor is reduced most on reducing the temperature from 298 to 16 K, whereas the thermal motion of the D nuclei is hardly affected. A comparison with the room-temperature result confirms the accuracy of the molecular-geometry measurement, and shows a molecular reorientation of over 1 o between 16 and 298 K.

Structural and excited-state properties of oligoacene crystals from first principles

“…For the smallest acenes, low-temperature data (T 14 K) are available in the CSD under the entries BENZEN14, NAPHTA31, and ANTCEN16, from Refs. [95,104,105]. Reference [164] also reports low-temperature data for benzene, consistent with the data of Ref.…”

“…These are compared to low-temperature experimental data, for T 16 K from Refs. [95,104,105] and extrapolated to 0 K as indicated in Appendix A (in black filled circles). For two pentacene polymorphs and hexacene, only experimental data at T 90 K is available [94,97,98] (in dark gray stars).…”

The temperature dependence of the anharmonic properties of crystalline naphthalene-d8

“…The implicit assumption in this constraint is that the molecular geometry and size do not change between 5 K and room temperature. This is given considerable support by a recent low-temperature study of anthracene-d~0 (Chaplot, Lehner & Pawley, 1982) where no significant change in the symmetry-constrained molecule was observed on comparison with the roomtemperature result of Lehmann & Pawley (1972), although the data contained sufficient information for significant molecular distortions to be observed through an unconstrained refinement.…”

X-ray diffraction study of the crystal structure of the π-molecular compound pyrene...pyromellitic dianhydride at 19 K

“…We have found only one single-crystal structure analysis of an aromatic hydrocarbon at temperatures below 20 K which can be used for purposes of comparison -anthracene at 16 K by neutron diffraction (Chaplot, Lehner & Pawley, 1982 …”