Crystal structure of 5,15-dihexyl-5,15-dihydrobenzo[2,1-b:4,3-c′]dicarbazole hexane 0.375-solvate

In the title compound, two helicenes form a porous structure with molecules of hexane inserted into the holes.

The title compound, C 38 H 40 N 2 Á0.375C 6 H 14 , crystallizes in the monoclinic space group P2 1 /c and has a host-guest structure with the helicene molecules forming a porous structure and molecules of hexane inserted into the holes. The dihedral angles between the two carbazole sections of the right-and left-handed helicenes are 27.44 (3) and 25.63 (3) , respectively. There are no classicalinteractions or hydrogen-bonding interactions present between adjacent molecules in the crystal structure. The hexane solvent molecule shows positional disorder.

Chemical context
-conjugated organic molecules have received a great deal of attention over the past few decades owing to their applications in organic field-effect transistors (Qi et al., 2008;Upadhyay et al., 2016) and organic light-emitting diodes (Hong et al., 2016;Konidena et al., 2015). 5,15-Dihexyl-5,15-dihydrobenzo-[2,1-b:4,3-c 0 ]dicarbazole 0.375-hexane, 1Á0.375-hexane, with a carbazole unit as the primary building block was designed based on the following factors. Firstly, carbazole is a cheap chemical material with a rigid and planar structure, and high thermal and electrochemical stabilities (Konidena et al., 2017). Secondly, introducing sufficient hexyl substituents to the helical core can enhance the solubility in common solvents drastically (Luo et al., 2018) and suppress close-packing in the solid state (Chen et al., 2017). Thirdly, a helical molecular geometry results in a non-planar, twisted structure, which decreases molecular aggregations and effectively hinders excited-state fluorescence quenching (Hua et al., 2015;Shi et al., 2012). Highly fused conjugated acenes can provide a high charge-carrier transport property as the conjugation length is increased (Pho et al., 2012). Of these compounds, helicene derivatives have been extensively applied in molecular recognition (Liu et al., 2018) and in photoresponsive cholesteric liquid crystals (Kim et al., 2017). As a result of their contribution to the development of chemical separations (Steed et al., 1994), topochemical reactions (Toda, 1995), biomimicry (Ghadiri et al., 1994) and so on, the design and synthesis of host-guest complexes has attracted intense interest. The recrystallization method provides a way of acquiring such complexes (Tanaka et al., 2000;Tanaka et al., 1995). By slow evaporation from a mixed solution of hexane and dichloromethane, we fortuitously obtained single crystals ISSN 2056-9890 of the title compound 1Á0.375 hexane. Despite attempting to grow single crystals via several methods, we did not obtain any crystal structures of solvent-free host molecules, indicating that interactions between host and guest molecules are an important factor in crystal growth.

Structural commentary
The title compound ( Fig. 1) crystallizes in space group P2 1 /c with two chiral helicene molecules and a partially occupied hexane molecule in the unit cell. The host molecule is a carbazole-based diaza[7]helicene whose geometrical parameters are similar to those of 5,15-dihexyl-5,15-dihydrobenzo[2,1-b:4,3-c 0 ]dicarbazoleÁ(cyclohexane) 0.5 with a 2:1 stoichiometry of host and guest molecules (Shi et al., 2012). However, the proportion of host and guest molecules in the title compound is 2:0.75 rather than 2:1, indicating that less hexane solvent is wrapped in the holes. In the right-handed helicene (containing N1, N2), the average C-C bond length [1.428 (3)

Supramolecular features
The title molecules are staggered and stacked in a face-to-face manner extending along the b-axis direction (see Fig. 2). The helicenes are packed forming a one-dimensional porous structure with hexane molecules located in the holes. No classicalinteractions or hydrogen bonding occur between adjacent molecules because of the non-planar screw structure and the steric effects of long substituted hexyl chains.  The molecular structure of the title compound with the atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

Refinement details
Crystal data, data collection and structure refinement details are summarized in Table 1. All H atoms were placed in geometrically calculated positions and refined using a riding model: C-H = 0.93-0.97Å (for CH 2 groups) or 0.96 Å (for CH 3 groups) with U iso (H) = 1.2U eq (C) or 1.5U eq (C-methyl). The hexane solvent molecule shows positional disorder. The carbon atoms could not be determined reliably from the difference-Fourier map. They were refined at their found Reaction scheme.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.