Structure and Properties of 9,14,15,16,17,18,19,20-Octahydro-9,14[1′,4′]-benzenobenzo[b]triphenylene

Abstract

]-benzenobenzo [b]triphenylene, C 28 H 24 , was prepared by hydrogenation of the 4 +4 photocycloadduct of dibenz [a,c]anthracene and 1,3-cyclohexadiene with Pt/C in ethyl acetate. The X-ray diffraction analysis shows that the compound crystallizes in the monoclinic space group 2 1 / with the geometric parameters of = 11.0090(17)Å, = 13.733(2)Å, = 13.091(2)Å, and = 109.583(13)∘ . In addition to several close intramolecular contacts involving hydrogens derived from the dibenzanthracene moiety, long interannular C-C single bonds of about 1.593Å are present. These bonds are shorter by about 0.18Å than the corresponding bonds in the unsaturated precursor, which can be attributed to reduced strain in the more saturated polycyclic ring system. Anisotropic shielding of the four endo-methylene hydrogens in the 1 H NMR spectrum is larger for the two hydrogens lying above the phenanthrene unit, which resonate at 1.03 ppm, than those above the benzenoid ring, which resonate at 1.24 ppm. Theoretical calculations reproduce the geometry with good agreement.