Zwitterionic 1-{(1E)-[(4-hydroxyphenyl)iminio]methyl}naphthalen-2-olate: crystal structure and Hirshfeld surface analysis

Abstract

The title zwitterion, C 17 H 13 NO 2 (systematic name: 1-{(1E)-[(4-hydroxyphenyl)-iminiumyl]methyl}naphthalen-2-olate), features an intramolecular chargeassisted N + -HÁ Á ÁO À hydrogen bond. A twist in the molecule is evident around the N-C(hydroxybenzene) bond [C-N-C-C torsion angle = 39. 42 (8) ] and is reflected in the dihedral angle of 39.42 (8) formed between the aromatic regions of the molecule. In the crystal, zigzag supramolecular chains along the a axis are formed by charge-assisted hydroxy-O-HÁ Á ÁO(phenoxide) hydrogen bonding. These are connected into a layer in the ab plane by charge-assisted hydroxybenzene-C-HÁ Á ÁO(phenoxide) interactions and -contacts [intercentroid distance between naphthyl-C 6 rings = 3.4905 (12) Å ]. Layers stack along the c axis with no specific interactions between them. The Hirshfeld surface analysis points to the significance CÁ Á ÁH contacts between layers. Chemical contextSchiff bases derived from o-hydroxynaphthalehyde have attracted significant attention owing to their biological properties, such as anti-tumour activity (Richardson & Bernhardt, 1999;Gou et al., 2015), and their photophysical properties, such as thermo-and photochromism (Matijević-Sosa et al., 2006). Furthermore, the physical properties of these molecules led to their application in various areas of materials science, such as in the control and measurement of radiation intensity, display systems and optical memory devices (Dü rr, 1989;Hadjoudis & Mavridis, 2004). These Schiff bases have also been used as tools for assessing the nature of hydrogen bonding (Richardson & Bernhardt, 1999), as well as ketoamine and phenol-imine tautomerism (Ü nver et al., 2000) in related molecules. In view of these various applications, our recent investigations have focused on the structure determination of Schiff bases of this type, e.g. of (E)-N-[(2-methoxynaphthalen-1-yl)methylidene]-3-nitroaniline (Bhai et al., 2015). As a continuation of these studies, the crystal and molecular structures of the title compound, (I), are described herein along with an analysis of the Hirshfeld surface, performed in order to gain more information on the nature of the molecular packing. Structural commentaryThe molecular structure of (I) is shown in Fig. 1. Crystallography established the molecule to exist in a zwitterionic ISSN 2056-9890 form with the putative H atom of the naphthyl-hydroxy group being located on the imine-N atom. This assignment is supported by the short C9-O2 bond length of 1.283 (2) Å . The molecule features two planar regions connected by an imine (iminiumyl) bridge; the configuration about the imine bond [C1 N = 1.308 (2) Å ] is E. The twist in the molecule occurs around the N1-C2 bond, is seen in the value of the C1-N1-C2-C7 torsion angle of 31.1 (3). The dihedral angle between the two aromatic regions is 39.42 (8) . The coplanar relationship between the imine and naphthyl residues is stabilized by an intramolecular charge-assisted N + -HÁ Á ÁO À hydrogen bond, Table 1. Supramolecular featuresThe most pr...