Synthesis, crystal structure and Hirshfeld surface analysis of naphthalene-2,3-diyl bis(3-benzyloxy)benzoate

In the title compound, C38H28O6, the dihedral angles between the naphthalene ring system and its pendant benzyloxy rings A and B are 88.05 (7) and 80.84 (7)°, respectively. The dihedral angles between the A and B rings and their attached phenyl rings are 49.15 (8) and 80.78 (8)°, respectively. In the extended structure, the molecules are linked by weak C—H⋯O and C—H⋯π bonds and π–π stacking interactions, which variously generate C(11) chains and (12) loops as part of a three-dimensional network. The Hirshfeld surface [fingerprint contributions = H⋯H (42.3%), C⋯H/H⋯C (40.3%) and O⋯H/H⋯O (15.7%)] and intermolecular interaction energies are reported, with dispersion, E dis at −428.6 kJ mol−1 being the major contributor.


Chemical context
Naphthalene, biphenyl or benzene rings can act as rigid cores in liquid crystal molecules. A variety of banana-shaped, bowshaped or bent-core ferroelectric liquid crystals were developed by incorporating a benzene ring as a rigid core (Noiri et al., 1996;Srinivasa et al., 2017). These types of compounds form lamellar and/or columnar mesophases (Szydlowska et al., 2003) and they have been subjected to experimental and theoretical studies (Reddy et al., 2006;Vaupotič, 2006). Liquid crystalline materials with a bent-core molecule are attractive because they exhibit good physical properties and possess two-dimensional smectic phases that display qualitatively different physical properties than calamatic ferroelectric liquid crystals.
Our team is studying new bent-core liquid crystals with naphthalene rings as a rigid core (Srinivasa et al., 2018) and, as part of that work, we have performed a simple coupling reaction between 1,2-dihydroxynaphthalene and 3-benzyloxybenzoic acid to construct the title molecule. It is a benttype non-liquid crystal material, possibly due to the absence of alkyl chains/polar moiety at the ends of the molecule.

Supramolecular features
In the crystal, the molecules are linked by numerous C-HÁ Á ÁO and C-HÁ Á Á interactions (Table 1). Prominent packing features include a C(11) chain (arising from the C21-H21Á Á ÁO2 ii hydrogen bond), which runs along [010], and centrosymmetric R 2 2 (12) loops (arising from the C9-H9Á Á ÁO5 i hydrogen bond) between the molecules as shown in Fig. 2. These, and the C-HÁ Á Á interactions, link the molecules into a three-dimensional network (see Figs. S1 and S2 in the supporting information).

Figure 1
The molecular structure of the title compound, showing displacement ellipsoids drawn at the 50% probability level.
the title compound were calculated at the HF/3-21G quantum level of theory in CrystalExplorer. The four energy variables that make up the total intermolecular interaction energy (E tot ) are electrostatic (E ele ), polarization (E pol ), dispersion (E disp ) and exchange-repulsion (E rep ), and the cylinder-shaped energy frameworks represent the relative strengths of the interaction energies in individual directions, as well as the topologies of pairwise intermolecular interaction energies within the crystal (Mackenzie et al., 2017). The energies between molecular pairs are depicted as cylinders connecting the centroids of two molecules, with the radius of the cylinder equal to the amount of interaction energy between the molecules (Wu et al., 2020). The net interaction energies for the title compound are E ele = À56.3 kJ mol À1 , E pol = À30.4.0 kJ mol À1 , E dis = À428.6 kJ mol À1 and E rep = 160.4 kJ mol À1 , with a total interaction energy E tot of À333.3 kJ mol À1 . Therefore, E dis is the major interaction energy in the title compound. The energy framework showing the electrostatic potential force, dispersion force and total energy diagrams are shown in Fig. 5. The cylindrical radii are proportional to the relative strength of the corresponding energies and they were adjusted to the same scale factor of 50 with a cutoff value of 5 kJ mol À1 . Energy frameworks calculated for the title compound, viewed along the a-axis direction, showing (a) Coulomb potential force, (b) dispersion force and (c) total energy diagrams. The cylindrical radii are proportional to the relative strength of the corresponding energies and they were adjusted to a cutoff value of 5 kJ mol À1 .

Figure 3
The Hirshfeld surface of the title compound mapped over d norm .
WAFSEF and WAFSIJ (Rutherford et al., 2020). There exist intermolecular interactions dominated bystacking and C-HÁ Á Á interactions involving the arene rings in the benzoate fragments and the arene ring in the tetrahydronapthalene moiety. A 'thermosalient phase transition effect' was studied in the compounds coded QIBMUM and QIBMUM01-QIBMUM06 (Tamboli et al., 2013), which feature a naphthalene-2,3-diyl bis(4-fluorobenzoate) fragment. The presence ofstacking and C-HÁ Á ÁO and C-HÁ Á ÁF interactions appear to play an important role in determining the molecular conformations. The crystal structure analyses of the polymorphic structures coded DOPPAB, DOPPAB01, DOPPAB02, DOPPOP, DOPPOP01 and DOPQAC (Tamboli et al., 2018) revealed weak intermolecular interactions, such as C-HÁ Á ÁO, C-HÁ Á Á andstacking, as also seen in the title molecule. These interactions are actively involved in molecular aggregation, which results in the polymorphic modifications, if they are subjected to thermal transformation. Here, all the molecules crystallize in the space group Pbcn or P2/c. The crystal structure analyses of IJAGIJ01 to IJAGIJ05 (Tamboli et al., 2014) are polymorphs of isomeric napthalene-2,3-diol ditoluates, in which the intermolecular interactions, such as C-HÁ Á ÁO, C-HÁ Á Á andstacking, are similar to the interactions present in the title molecule.

Synthesis and crystalization
Under an inert atmosphere, 1,2-dihydroxynaphthalene (1.00 mmol), a catalytic amount of 4-dimethylaminopyridine and 3-benzyloxybenzoic acid (2.00 mmol) were dissolved in 50 ml of dry dichloromethane (DCM). The above mixture was stirred for 2 h at room temperature with a solution of N,Ndicyclohexylcarbodiimide (1.2 mmol) in DCM (20 ml). Filtration was used to remove the precipitated N,N-dicyclohexylurea and the solvent was evaporated. To obtain the pure product, the solid residue was purified using column chromatography on silica gel with DCM as an eluent, followed by recrystallization from ethyl alcohol solution.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were positioned geometrically (C-H = 0.93 Å ) and refined as riding with U iso (H) = 1.2U eq (C).  program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL (Sheldrick, 2015b); molecular graphics: Mercury (Macrae et al., 2020); software used to prepare material for publication: SHELXL (Sheldrick, 2015b). 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.