Crystal structure of 1,3-diphenyladamantane and trans-1,4-diphenylcyclohexane: torsion angles about C–Ph bonds in α,ω-diphenyl(alicyclic hydrocarbon)

Abstract

The orientation of the two phenyl rings in α,ω-diphenylalkanes with rigid carbon skeletons is investigated through characterization of the crystal and molecular structures of 1,3-diphenyladamantane ( 1) and trans-1,4-diphenylcyclohexane ( 2). The two phenyl rings in 1 have different conformations about the C–Ph bonds, with torsion angles between the phenyl ring and the C1–C2–C3 plane of 0.65 and 71.7°. A hydrogen atom at the meta-position of one of the phenyl rings contact intermolecularly with a tertiary hydrogen atom at C5 of adamantane within the sum of van der Waals radii. Due to the helical conformation, the short CH⋯HC contacts (2.231 Å) construct supramolecular triple helical strands. In contrast to 1, the phenyl rings in 2 have identical configurations, with equatorial position and bisected conformation as expected from density functional calculations. The molecular packing of 2 exhibits a herringbone pattern of (aromatic)C–H⋯π contacts.