Crystal structure of tris[4-(naphthalen-1-yl)phenyl]amine

In the crystal, two molecules of the title compound form an inversion dimer, through C—H⋯π interactions, which further interacts with adjacent dimers to form a one-dimensional column structure.

In the title molecule, C 48 H 33 N, the central N atom shows no pyramidalization, so that the N atom and the three C atoms bound to the N atom lie almost in the same plane. The three para-phenylene rings bonded to the N atom are in a propeller form. All of the naphthalene ring systems are slightly bent. In the crystal, molecules form an inversion dimer, through two pairs of C-HÁ Á Á interactions, which further interacts with the adjacent dimer via another two pairs of C-HÁ Á Á interactions, forming a column structure along the a axis. There are no significant interactions between these column structures.

Chemical context
Triarylamines (TAAs) having various substituents at their para-positions are widely known to give the corresponding stable cation radicals upon chemical or electrochemical one electron oxidation (Seo et al., 1966). -Extended TAAs with extra aromatic rings at the periphery have received considerable attention as key components in the fields of organic electroluminescence devices. Among them, the title compound was first synthesized by Kwon et al. (2010) as a hole-transporting material in organic light-emitting diodes. Recently, phosphorescent organic light-emitting diodes were also reported by using the title compound as the hole-transporting material (Krucaite et al., 2019). Until now, no crystal structure of this compound has been reported. We report herein the crystal structure of the title compound.

Synthesis and crystallization
The title compound was prepared by a modification of the previously reported Suzuki-Miyaura coupling reaction (Kwon et al., 2010). Tris(4-bromophenyl)amine (2.00 g, 4.15 mmol), 1naphthylboronic acid (3.57 g, 20.7 mmol), tetrakis(triphenylphosphine)palladium(0) (240 mg, 0.21 mmol), K 2 CO 3 (2.87 g, 20.7 mmol), toluene (42 mL) and water (10.4 mL) were placed in a 100 mL round-bottom flask. After the solution was purged with nitrogen for 10 minutes, it was heated at 373 K under nitrogen for 24 h. The reaction mixture was extracted with ethyl acetate. After drying over anhydrous Na 2 SO 4 , the organic layer was evaporated. The residue was redissolved in a small amount of ethyl acetate. The addition of a large amount  Table 1 Hydrogen-bond geometry (Å , ).

Figure 4
A packing diagram of the title compound viewed along the b axis, showing the column structure. The C-HÁ Á Á interactions are shown as dashed lines. H atoms not involved in these interactions have been omitted for clarity.  of methanol gave the pure product as a white precipitate (845 mg, 1.35 mmol, 33%). Colorless single crystals suitable for X-ray diffraction were obtained by means of the vapor diffusion method from chloroform as a rich solvent and n-hexane as a poor solvent after standing for one week.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. C-bound H atoms were placed in geometrically calculated positions (C-H = 0.95 Å ) and refined using a riding model with U iso (H) = 1.2U eq (C). One outlier (011) (Altomare, et al., 1994); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015); molecular graphics: PLATON (Spek, 2020), publCIF (Westrip, 2010); software used to prepare material for publication: CrystalStructure (Rigaku, 2016).  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 was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F 2 . R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 sigma(F 2 ) is used only for calculating Rfactor (gt).