Budy Stephen M, Nichol Gary S, Loy Douglas A
Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ 85721, USA.
Acta Crystallogr C. 2012 Jan;68(Pt 1):o23-7. doi: 10.1107/S0108270111051900. Epub 2011 Dec 9.
The title compounds, C(66)H(46), (I), and C(66)H(42)F(4), (II), are polyphenylated arylenes synthesized by one-step Diels-Alder cycloaddition reactions. In both structures, all molecules lie on crystallographic inversion centers. In the case of (I), there are two half-molecules present in the asymmetric unit, (IA) and (IB); the geometry of each half-molecule differs principally in the magnitudes of the dihedral angles between mean planes fitted through the central aryl ring and the pendant phenyl rings. The crystal used was a non-merohedral twin, with a refined twin scale factor of 0.460 (8). The dihedral angle between the plane of the central tetrafluorinated ring and the adjacent tetraphenylated ring in (II) is 83.87 (4)°, significantly greater than the dihedral angles of 49.89 (12) and 54.38 (10)° found in the two half-molecules in (IA) and (IB), respectively, and attributed to intermolecular C-H···F hydrogen bonding in (II). Intermolecular C-H···π bonding is found in (I). Two interactions have the C-H bond oriented towards the centroid (Cg) of a butadiene fragment of a phenyl ring; both H···Cg distances are approximately 2.68 Å and the interactions connect adjacent molecules into stacks in the c-axis direction. The composition of the stacks alternates, i.e. (IA)-(IB)-(IA)-(IB) etc. A third, weaker, C-H···π interaction and a phenyl-phenyl close contact connect each end of the long molecular axes of (IB) with an adjacent molecule of (IA) into chains which run perpendicular to the (140) and ( ̅140) planes. C-H···F interactions in (II) have the most profound influence on the molecular and crystal structure, the main effect of which is the above-mentioned increase in the dihedral angle between the plane of the central tetrafluorinated ring and the adjacent tetraphenylated ring. C-H···F interactions have refined H···F distances of 2.572 (15) and 2.642 (16) Å, with approximate C-H···F angles of 123 and 157°, respectively. These form a hydrogen-bonded ribbon structure which propagates in the b-axis direction.
