The Crystal Structure of the 1:1 Complex of Pyromellitic Dianhydride with trans-Stilbene

Abstract

Abstract The 1: 1 complex of pyromellitic dianhydride with trans-stilbene crystallizes in the space group P21/c with two pairs of the component molecules in a unit cell with dimensions of a=12.48, b=6.33, c=13.17 Å, and β=111.6°. The structure was solved from a three-dimensional |E|2 Patterson synthesis and refined by a block-diagonal least-squares method to a final R value of 0.12 for 1635 reflections. In the trans-stilbene molecule, the plane containing the central ethylene group makes an angle of 11.5° with the phenyl plane. The non-planarity of the trans-stilbene molecule seems to be largely due to a steric repulsion between the hydrogen atom attached to the ethylene moiety and that at the 6 and 6′ position in the phenyl group. The pyromellitic dianhydride molecule is approximately planar. The component molecules are stacked alternately in infinite columns along the a axis. The average spacing between the phenyl plane of trans-stilbene and the molecular plane of pyromellitic dianhydride is 3.59 Å, and these palnes make an angle of 4.8° with each other. The relative arrangement of the component molecules in the crystal differs from that observed in the crystal of the anthracene, pyrene, or perylene complex with pyromellitic dianhydride. The van der Waals forces are considered to be more important than the charge transfer force in determining the relative arrangement of the component molecules in this crystal.