The crystal and molecular structure of quaterrylene

Quaterrylene (III) is isotypic with perylene (I); it crystallizes in the monoclinic system with a = 11·25, b = 10·66, c = 19·31 Å, β = 100·6°, and with four molecules per unit cell and the space group P21/a. The crystal structure has been determined by two-dimensional methods. In the b-axial projection a majority of the carbon atoms are resolved, and, since the molecule lies with its greatest length almost exactly perpendicular to this axis, the lengths of the peri-bonds connecting the naphthalenic residues have been determined with moderate accuracy. The mean value is assessed at 1·53 ± 0·01 Å, which is significantly larger than current theory predicts. Possible reasons for this difference are discussed.