Crystal structures of 4-(2/3-methoxyphenoxy)phthalonitrile

The syntheses and crystal structures are reported of 4-phenoxy-substituted phthalonitriles with methoxy groups in the ortho- and meta-positions of the terminal benzene rings. Short contacts play a more decisive role in the molecular packing compared to van der Waals interactions.


Chemical context
Phthalonitriles are a class of organic compounds with high thermal and oxidative stability (Laskowski et al., 2016). That destruction only takes place at high temperatures facilitates using these molecules as building blocks for polymer composite materials with a high degree of cross-linking (Wang et al., 2019). In addition, phthalonitriles are among the most promising precursors for the preparation of phthalocyanine complexes of various structures based on building blocks derived from them.
Phthalocyanines, as a result of their structural features and the possibility of introducing almost any functional moieties to their periphery, have found wide application in areas of societal and industrial importance such as catalysis, optics, medicine, light industry, etc. (Botnar et al., 2020(Botnar et al., , 2021. Substituted phthalocyanines, which attract the most attention, however, are obtained from phthalonitriles with various fragments in the 3 and 4 positions. Thus, it is of general interest to obtain functionally substituted nitriles and to study their properties. Here, we report the crystal structures of methoxyphenoxyphthalonitriles with the methoxy group in the meta-and ortho-substitution, respectively, which have been prepared for the synthesis of the corresponding substituted phthalocyanines. X-ray diffraction data for the ortho-isomer are already described in the literature (Agar et al., 2007). However, no discussion is provided of the influence of the structure of the substituted nitrile on the crystal-packing stabilization. The presence of oxygen atoms in the composition of the molecules leads to the formation of interesting intermolecular interactions, which are discussed in this communication.

Supramolecular features
In 4-(2-methoxyphenoxy)phthalonitrile, stabilization of the intermolecular packing is realized mainly through the formation of hydrogen bonds between the donor C8-H8A group of the A ring with the cyano group (C14 N2) acceptor attached to the A ring of an adjacent molecule (C8-H8AÁ Á ÁN2; symmetry operator: x + 1 2 , Ày + 3 2 , Àz + 1; Fig. 3, Table 1). The formation of a weaker but bifurcated intermolecular hydrogen-bonding interaction C11-H11Á Á ÁO1/O2(À 1 2 + x, 1 2 À y, 1 À z) is also found in this structure, which additionally supports the packing. In the case of 4-(3-methoxyphenoxy)phthalonitrile, because of the favorable spatial arrangement of two A rings of neighboring molecules, stabilization occurs largely through respectiveinteractions. The planes of the A rings of two neighboring molecules are parallel to each other, but offset (angle between the ring normal and the The molecular structure of m-4-(2-methoxy phenoxy)phthalonitrile, showing the atom labeling. Displacement ellipsoids are drawn at the 50% probability level.
centroid vector is 22.6 with a slippage of 1.41 Å ). The distance between the centers of the A rings is 3.6632 (6) Å (centroidcentroid distance). These geometric characteristics imply the presence of a significant intermolecularattraction (Janiak, 2000). The hydrogen atom of the aromatic C11-H11 moiety of one and the O1 oxygen atom of the adjacent molecule may be engaged in additional bidirectional contacts ( Fig. 4), which support theinteraction as well as its slippage. In both cases, a number of weaker hydrogen-bonding contacts are observed, comprising additional contributions to the stabilization of the crystal structures. Thus, the packing of the ortho-isomer exhibits in total eight intermolecular hydrogen-bonding interactions, while for the meta-isomer, in addition to theinteraction, five hydrogen bonds are observed (Tables 1, 2 Ocak İskeleli, 2007). The meta-isomer is also a phthalonitrile dimer now bridged by the m-phenoxy moiety (refcode: HAMVIB; Deveci et al., 2004). Notably, with regard to the phthalonitrile dimers, --stacking is observed for the metaisomer but not for the ortho-isomer; the same observation was made for the two title compounds. A view along the b axis of the crystal packing of m-4-(2-methoxyphenoxy)phthalonitrile. Intermolecular hydrogen bonds have been removed for clarity. Symmetry codes: (i) Àx þ 1; Ày; Àz þ 1; (ii) Àx þ 2; Ày þ 1; Àz þ 2; (iii) x À 1; y; z; (iv) Àx þ 1; Ày þ 1; Àz þ 2.

Figure 6
A view along the b axis of the crystal packing of o-4-(3-methoxyphenoxy)phthalonitrile. Intermolecular hydrogen bonds have been removed for clarity.

Synthesis and crystallization
Materials and physical methods: All reagents were purchased from Sigma-Aldrich. Reaction progress was monitored by thin-layer chromatography (TLC) on silica-gel plates. Synthesis of substituted phthalonitriles: 4-nitrophthalonitrile and 2/3-methoxyphenol in a 1:1 molar ratio were placed in a flask and dissolved in DMF. Further, after complete dissolution of the reagents, 1 mol of potassium carbonate and 1/3 portion of water (in relation to DMF) were added to the mixture. The reaction mass was stirred at 353-363 K for 2.5 h, after which it was cooled to 278 K and poured into a threefold excess (by volume) of 15% aqueous NaCl solution. The precipitate was filtered off, recrystallized from 50% aqueous 2-propanol solution and then dried at 343 K. As a result, light crystals of 4-(2-methoxyphenoxy) phthalonitrile (75%) and 4-(3-methoxyphenoxy) phthalonitrile (89%) were obtained, respectively. Crystals were obtained by slow evaporation of solvent from a saturated solution of phthalonitriles in chloroform.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. All hydrogen atoms were placed in calculated positions and were refined using a riding model [U iso (H) = 1.5U eq (C) for CH 3 groups and U iso (H) = 1.2U eq (C) for other groups).

4-(2-Methoxyphenoxy)benzene-1,2-dicarbonitrile (o-C15H10N2O2)
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.