Conformation of Condensed Polycyclic Aromatic Hydrocarbons. II. The Molecular and Crystal Structure of Violanthrene B (Dibenzo[a, rst]naphtho[8,1,2-cde]pentaphene)

The title compound, C34H18, has been obtained by reducing violanthrone B, a byproduct in the synthesis of violanthrone. Its structure has been determined by on X-ray analysis. The space group is P21/c, with unit-cell dimensions a=25.78(1), b=3.807(5), c=19.975(8) A, β=96.55(3)°, and Z=4. The structure was solved by the direct method and refined by a block-diagonal least-squares method to an R value of 0.076 on the basis of 1242 independent reflections. The molecules are largely distorted from a planar structure owing to a steric repulsion between the intramolecular overcrowded hydrogen atoms. Also, they are stacked face-to-face to form a column structure along the b-axis.