Crystal structure and Hirshfeld surface analysis of diethyl 5-(2-cyanophenoxy)isophthalate

The title compound is non-planar, subtending a dihedral angle of 82.38 (4)° between the plane of hydroxy isophthalate-based ester and that of the benzonitrile moiety. The molecule is bent at the ether linkage, with a Caryl—O—Caryl bond angle of 116.74 (11)°. In the crystal, molecules are linked by C—H⋯O hydrogen bonds and other weak interactions forming a supramolecular framework.


Chemical context
5-Hydroxyisophthalic acid and its derivatives have been used in the synthesis of several organic ligands. This type of ligand has an isophthalate moiety, which has oxygen-rich carbon chains that are sufficiently reactive to incorporate functionality, followed by conjugation with biomolecular compounds (Calderon et al., 2010;Khandare et al., 2012). Carboxylatecontaining ligands have been used for the synthesis of coordination polymers because of their flexible nature. The flexibility of the ligand and hardness of metal ions improve the stability of coordination polymers (Ahmad et al., 2012). Coordination polymers have been used in various types of applications as a result of their physical properties, which include ferromagnetic behaviour, antiferromagnetic ordering, spin canting and metamagnetism (Wang et al., 2005;Liu et al., 2010). Several types of framework have been obtained, such as metal complexes, clusters, and metal-organic frameworks by linking of the flexible organic linker and metal ion, leading to interesting magnetic properties (Cheon & Suh, 2009;. Organic ligands containing ether linkages have been used to synthesize magnetic materials because these types of organic ligands exhibit a binding ability that can efficiently transmit magnetic coupling (Coronado et al., 2000;Masciocchi et al., 2009;Yu et al., 2010).

Structural commentary
The molecular structure of the title compound is shown in Fig. 1. The compound crystallizes in the monoclinic space group P2 1 /c. The asymmetric unit contains one unit of 5-hydroxy-isophthalic acid diethyl ester and one unit of benzonitrile, connected by an ether bridge linkage. The molecule is non-planar, with a C12-O5-C14 bond angle of 116.74 (11) at the ether group, and a C14-O5-C12-C13 torsion angle at the bridge of À97.37 (2) . The C12-O5 bond length, 1.4025 (17) Å , is comparable to the C-O bond lengths obtained for similar ligands. The C3-O1 and C3-O2 bond lengths are 1.3377 (18) and 1.2061 (19) Å , respectively, and are in the expected ranges (Cambridge Structural Database; Groom et al., 2016).

Hirshfeld analysis
The Hirshfeld surface analysis (Spackman & Jayatilaka, 2009) and the associated two-dimensional fingerprint plots (McKinnon, et al., 2007) were performed with Crystal Explorer17 (Turner et al., 2017) to investigate the intermolecular interactions and surface morphology of the crystal structure. The Hirshfeld surface mapped over d norm (Fig. 4) in the colour range À0.174 to 1.315 a.u. from red (shorter distance than the sum of van der Waals radii) and white to blue (longer distance than the sum of van der Waals radii). The bright red spot on the d norm surface corresponds to a weak interaction e.g. hydrogen bonding, blue indicates close contacts and a white spot shows van der Waals interactions. In the crystal there are three major types of interaction (HÁ Á ÁH =  Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
A view along the b axis of the crystal packing of the title compound. Hydrogen bonds are shown as dashed lines.

Figure 3
A view along the a axis of the crystal packing of the title compound. The C-HÁ Á Á and other weak interactions are indicated by dashed lines.

Figure 1
The molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 50% level.

Database survey
A search of the Cambridge Structural Database (CSD version 5.39, update of May 2018; Groom et al., 2016) for 5-hydroxyisophthalic acid derivatives gave 38 hits for structures that include atomic coordinates. In most of the derivatives, the phenolic group is replaced by an alkoxy, a substituted alkoxy or a substituted phenoxy moiety. Only in three of the 5-hydroxy-isophthalic acid derivatives is the carboxyl group modified: IDIYIE (Petek et al., 2006), NUHTAM (Feng et al., 2009), EVIBOB (Yang et al., 2011). In all these compounds, the hydroxyl groups of the carboxyl moieties have been replaced by methoxy groups and the phenolic group is replaced by a substituted alkoxy or a substituted phenoxy moiety.

Synthesis and crystallization
5-Hydroxyisophthalic acid diethyl ester (3.7 g, 14.9 mmol) was mixed with dried K 2 CO 3 (3.3g, 22.3 mmol) in a 100 ml roundbottom flask under an inert atmosphere and then treated with dry DMF (20 ml) . The mixture was stirred for 30 minutes at 353 K followed by addition of 2-fluoro-benzonitrile (1.8 ml, 16.6 mmol) and the resulting mixture was stirred for 24 h in an oil-bath at 353 K. After this period, the solution was allowed to cool to room temperature and then poured into ice-cold water (100 ml) with vigorous stirring, to afford a white precipitate, which was collected by filtration, washed with water, and dried under vacuum. Yield: 4.6 g (90%). Melting point 325 K. The ligand was crystallized from a solution in ethanol, the resultant solution was filtered and kept for slow evaporation. After 2-3 weeks, block-shaped colourless crystal were obtained, which were suitable for single-crystal X-ray diffraction analysis.