3,12-Dimethoxy-5,6,9,10-tetrahydro-[5]helicene-7,8-dicarbonitrile

The complete molecule of the title compound, C26H20N2O2, is generated by a crystallographic twofold axis. The torsion angle between the terminal and central benzene rings is −32.5 (2)°. The torsion angle along the inner helical rim of the molecule is −18.8 (2)° with each other. The C⋯C distance between the terminal rings is 3.016 (2) Å. In the crystal, weak C—H⋯N hydrogen bonds are observed.

The complete molecule of the title compound, C 26 H 20 N 2 O 2 , is generated by a crystallographic twofold axis. The torsion angle between the terminal and central benzene rings is À32.5 (2) . The torsion angle along the inner helical rim of the molecule is À18.8 (2) with each other. The CÁ Á ÁC distance between the terminal rings is 3.016 (2) Å . In the crystal, weak C-HÁ Á ÁN hydrogen bonds are observed.

Comment
Helicenes are polycyclic aromatic hydrocarbons (PAHs) that consist of ortho-fused aromatic rings arranged in helical chiraliry. Applications of helicenes are ranging from catalyst to molecular machines. (Shen et al., 2012;Gingras, 2013).
The title compound is a derivative of pentahelicene in which two electron donor and two electron acceptor groups are added into the structure in order to improve its fluorescence quantum yield. Moreover, two rings connected to the central benzene ring are not fully aromatized and in a twist conformation. An application of a similar compound as an emitter for a light-emitting diode was reported (Sahasithiwat et al., 2010).
The geometric parameters of the title molecule agree well with reported similar structures (McIntosh et al., 1954;Wang et al., 1997;Stammel et al., 1999;Rajapakse et al., 2011). Half a molecule of the title compound belongs to asymmetric unit and a molecule is completed by the crystallographic twofold axis as shown in Figure

Refinement
All hydrogen atoms were placed in calculated positions and treated as riding atoms with C-H distances of 0.93 Å,0.97 Å, and 0.96 Å for aryl, methylene, and methyl H atoms, respectively. The H atoms were assigned Uiso = 1.2 Ueq(C) for aryl H, Uiso = 1.2 Ueq(C) for methylene H, and Uiso = 1.5 Ueq(C) for methyl H.  The molecular structure of the title compound showing 50% probability displacement ellipsoids for non-H atoms.
Symmetry code: (i) -x,y,1/2 -z.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.18 e Å −3 Δρ min = −0.19 e Å −3 Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.