Crystal structure of 4-(anthracen-9-yl)pyridine

The title compound, which crystallizes in the monoclinic C2/c space group with one half-molecule in the asymmetric unit, was synthesized by Suzuki–Miyaura cross-coupling reaction of 9-bromoanthracen-2-ylium with pyridin-4-ylboronic acid.


Chemical context
Anthracene and its derivatives constitute a very famous class of fluorophores that have been widely used in the development of functional fluorescent chemosensors because of their intriguing photophysical properties and chemical stability (Martínez-Má ñ ez et al., 2003). One of the most important steps in the rational molecule design of anthracene-based chemosensors is the judicious combination with functional chemical recognition moieties, which can be used for monitoring and quantifying of abnormal physiological changes at the subcellular level (Densil et al., 2018;Mondal et al., 2014;Anand et al., 2015;Shree et al., 2019). It has been found that 9,10-distyrylanthracene derivatives with restricted intramolecular rotations often lead to aggregation-induced emission characteristics (Lu et al., 2010). In recent years, there has been an increased effort to combine anthracene derivatives with N-or O-coordinated single ligands and other attractive mixed ligands in order to construct tunable fluorescent ligands (Dey et al., 2016;Yao et al., 2019). As part of our studies in this area, we report herein the synthesis and crystal structure of a fluorescent monopyridine ligand, C 19 H 13 N.

Structural commentary
As shown in Fig. 1, single-crystal X-ray diffraction analysis reveals that 4-(anthracen-9-yl)-pyridine crystallizes in the monoclinic C2/c space group with half molecule in the asymmetric unit (Table 1). In the structure of the title compound, the C-C bond lengths of the benzene ring range from 1.3534 (13) to 1.4352 (1) Å , and the C-N bond length is 1.3351 (11), which is comparable with the literature reported (Zhao et al., 2016). The bond angle of N1-C1-C2 is 124.161 (7) , closed to the ideal bond angle of 120 for benzene ring. The pyridine ring is inclined to the benzene ring at a dihedral angle of 71.64 (4) .

Supramolecular features
In the crystal, the hydrogen atom of anthracene ring contributes to the formation of a C7-H7Á Á Á contact with the pyridine ring (Table 1); the resulting cyclic centrosymmetric dimer is shown in Fig. 2. Subsequently, the paired C-HÁ Á Á(pyridine) hydrogen-bonding interactions connect neighboring dimers, resulting in an infinite 1-D linear chain ( Fig. 3), which is basis for extension of the dimensionality. As shown in Figs. 4 and 5, the crystal packing involves weak faceto-facestacking interactions [d(CgÁ Á ÁCg) = 3.6095 (7) Å ] between two benzene rings related by the symmetry operation 1 À x, y, 1 2 À z.

Figure 2
The hydrogen-bonded centrosymmetric dimer along the c axis.

Figure 3
View of the 1-D chain-like structure of the title compound along the c axis.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were positioned geome-trically (C-H = 0.93 Å ) and refined as riding with U iso (H) = 1.2U eq (C).

4-(Anthracen-9-yl)pyridine
Crystal data 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.