Molecular complexes. Part XXII. Crystal and molecular structure of the molecular complex of pyrene and chloranil

Abstract

The crystal and molecular structure of the 1 : 1 complex of pyrene and chloranil has been determined by three-dimensional X-ray diffraction methods. Crystals are monoclinic, a= 7·52 ± 0·02, b= 13·68 ± 0·03, c= 8·93 ± 0·02 Å, γ= 96·5 ± 0·2°, space group P2₁/b. The structure was solved from visually estimated photographic data by the symbolic addition method and refined by least squares to R 0·076 (1001 independent reflections). In the crystal alternate pyrene and chloranil molecules form stacks along the a axis. The mean separation of the molecular planes, which are inclined at 2·8°, is 3·46 Å. The relative orientations of donor and acceptor are close to those predicted for the maximisation of charge-transfer interactions.