Structural aspects of [2.2]heterophanes. Part I. Molecular structure of [2.2](2,6)pyridinophane

Abstract

The crystal and molecular structure of the title compound has been determined from three-dimensional X-ray diffractometer data. Crystals are orthorhombic with a= 13.49(8), b= 7.525(7), c= 11.24(8)Å, space group Pbca. The structure was solved by direct methods and refined by least squares techniques to R 0.047 for 616 independent reflections. The crystals are built up by discrete centrosymmetric molecules approaching C_2h symmetry. The pyridine rings are distorted towards an asymmetric boat conformation and are so arranged as to get a stepped geometry (N ⋯ N 2.54, inter-ring distance 2.22 Å). A significant stretching of the C–C bond length of the ethylene bridges, in a gauche conformation (63°), is observed (1.581 Å). The geometrical features are compared with those of free pyridine and other [2.2]phases.