1,5-Bis(piperidin-1-yl)-9,10-anthraquinone

In the centrosymmetric title compound, C24H26N2O2, the piperidine ring adopts a chair conformation and is inclined at a dihedral angle of 37.5 (1)°to the anthracene ring system. In the crystal, adjacent molecules are linked through C—H⋯π and π–π [centroid–centroid distances = 3.806 (1) Å] interactions, forming a layer parallel to the bc plane.


Related literature
Cg2 is the centroid of the C1-C6 ring. pigments, food colorants and textile dyes. Some of the anthraquinone derivatives have been used for medical purposes as anticancer drugs and antitumor or antiviral agents (Alves et al., 2004;Krohn, 2008). Finally, derivatives belonging to this group of compounds are applied in molecular and supramolecular chemistry as optical and electrochemical sensors (Czupryniak et al., 2012;Wannalerse et al., 2008). This wide variety of practical applications make anthraquinone derivatives an important object of research and natural target in organic synthesis.
The title compound has only half of molecule in the asymmetric part of the unit cell ( Fig. 1). In the crystal structure, each half of molecule is arranged around an inversion centre located in the middle of the quinone ring. In the molecule of the title compound, likewise in other 9,10-anthraquinone derivatives (Niedziałkowski et al., 2010;Niedziałkowski et al., 2011;Wnuk et al., 2012, Yatsenko et al., 2000, deviation of planarity of the anthraquinone skeleton is observed. In case of the title compound, such distortion is found to be 0.0834 (3) Å. The piperidine rings adopt a chair conformation, with ring-puckering parameters Q = 0.5680 (18) Å, Θ = 178.23 (18)° and φ = 207 (6)°. The mean planes of piperidine and anthracene ring systems are inclined at a dihedral angle of 37.5 (1)°. The neighboring anthracene moieties are parallel or inclined at an angle of 63.3 (1)° in the crystal lattice. In the crystal, the adjacent molecules are linked by C-H···π (Table   2, Fig. 2) and π-π [centroid-centroid distances = 3.806 (1) Å] (Table 3, Fig. 2) interactions, forming a layer parallel to the bc plane.

Experimental
To a solution of 1 g 1,5-bis(tosyloxy)-9,10-anthraquinone (1.823 mmol) in 50 ml of toluene 0.392 g of piperidine was added (4.775 mmol). The mixture was heated to 80°C. After 24 h the reaction mixture was cooled to room temperature.
The resulting mixture was filtered and the solvent was removed under reduced pressure. The residue was dissolved in dichloromethane (200 ml) and washed with water (3 x 200 ml). The organic layer was dried over anhydrous MgSO 4 and concentrated under reduced pressure to obtain a red solid residue. This solid was purified by flash column chromatography (SiO 2 , eluent: dichloromethane) to afford the 0.657 g (yield: 96%) of the title compound. Dark-red crystals suitable for X-ray investigations were grown from dichloromethane/methanol solution (1: 3434, 2940, 2855, 2813, 1648, 1582, 1423, 1381, 1226, 895, 710 (cm -1    The arrangement of the molecules in the crystal structure. The C-H···π and π-π interactions are represented by dotted lines. H atoms not involved in interactions have been omitted. [Symmetry codes: (i) -x, y -1/2, -z + 1/2; (ii) -x, -y, -z + 1.] where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.13 e Å −3 Δρ min = −0.14 e Å −3 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq C1 0.09986 (