The crystal structure of triphenylene

Abstract

Crystals of triphenylene are orthorhombic with four molecules in a unit cell of dimensions a = 13.17, b ---16-73, e = 5.26/~, space group P212121. The gross features of the structure, previously determined from two projections, have been confirmed using new three-dimensional data, the positional and isotropic thermal parameters of the carbon atoms have been refined by differential syntheses, and the hydrogen atoms have been located. There are small, but significant, deviations from a completely planar arrangement. These displacements are best described in terms of the plane of the central ring: atoms of two of the outer rings are displaced in one direction, and those of the third ring in the opposite direction from this plane. This slight molecular distortion is probably the result of intramolecular steric effects. The mean bond distances agree closely with the values predicted by valence-bond and molecular-orbital calculations. All the intermolecular separations correspond to normal van der Waals interactions.