The crystal structure of theπ-molecular compound pyrene :p-benzoquinone

Abstract

Pyrene : p -benzoquinone (C 16 H 10 :C 6 H 4 O 2 ) crystallizes in the tetragonal system, with cell constants a = 7.698(2), c = 25.570(5) Å, space group P 4 1 and four formula units per unit cell. The structure was solved by direct methods and refined to an R value of 0.048 for 778 observed reflexions. The pyrene and p -benzoquinone molecules are arranged alternately in mixed stacks, with interplanar spacing of 3.49 Å and an angle of 1.1° between molecular planes. The mixed stacks are arranged in sheets parallel to (001), successive sheets being related by the 4 1 axis. This type of arrangement of mixed stacks has not been encountered previously among π -molecular compounds. Neither the stacks nor their arrangement are centrosymmetric; as the component molecules are both centrosymmetric this constitutes a second unusual feature of this crystal structure.

Molecular compounds and complexes. VII. The crystal structure of anthracene:picric acid

“…7) and this suggests that the stacks vibrate as units in the crystal. In particular the r.m.s, amplitude of translational motion normal to the molecular planes is 0.16--0.17 A for both molecules [similar values have been found for the corresponding motion of the molecules normal to their planes in pyrene :benzoquinone (Bernstein, Regev, Herbstein, Main, Risvi, Sasvari & Turcsanyi, 1975)], and the r.m.s, translational amplitudes are approximately isotropic in the planes of both molecules. The r.m.s, libration amplitudes are about the same for both molecules.…”