Crystal Structure of a Benzyltrimethylammonium Chloride Complex with rac-1,1′-Bi-2-naphthol: The Generation of Weak Interactions by the Influence of a Benzyl Group

Abstract

Weak intermolecular non-covalent interactions between molecules are now being exploited for the synthesis of large supramolecular aggregates.1 These weak forces guarantee the structural and functional integrity of supramolecular systems. The supramolecular and crystal engineering approach have become popular due to its pharmaceutical significance, as well as its application in separation science, and biomembrane studies. Typically, many supramolecular chemists and crystal engineers have extensively reported on molecular recognition studies between phenol derivatives and quaternary alkyl ammonium salts using an inclusion crystallization technique,2,3 as well as a crystal engineering approach that involves the manipulation of hydrogen bonding patterns and packing fashions.4 Such studies have been utilized in employing knowledge concerning the separation of phenol derivatives in both chemical and pharmaceutical industries. Surprisingly, as per our search of the Cambridge Structure Database Ver. 5.34, 2013, no studies have been conducted on molecular recognition studies between a quaternary arylammonium halide (typically, benzyltrimethylammonium chloride, hereafter, BTMAC) with a phenol derivative (typically, rac-1,1′-bi-2-naphthol, hereafter, BNP), since such a study may reveal how the rigid aryl (benzyl) group may be utilized to influence the hydrogen bonding directionality of the alkyl {e.g. methyl (CH3)} groups of the ammonium cation onto a naphthol plane of BNP (non planar), and the enhance generation of weak C–H···π, and C–H···O interactions, as well as to know whether BTMAC is suitable for binding with phenol derivatives in a molecular recognition phenomena. Thus, this manuscript describes the aforementioned interest through studying the crystal structure of the BTMAC/ BNP complex. Crystals suitable for X-ray diffraction studies were obtained within five days by the slow evaporation of a warmed acetone/ ethylacetate (20 mL) mixture in which BTMAC (0.19 g, 1 mmol), and BNP (0.29 g, 1 mmol) were dissolved. Crystal data and data collection details are listed in Table 1. Data collection and cell refinement were carried out using DENZOSMN. The structure solution was carried out with direct methods using the program superflip within the CRYSTALS software suite, and refined by a full-matrix least-squares methods based on F2. All H atoms were located in electron density difference maps. The H atoms were positioned with idealized geometry with C–H = 0.93 – 0.99 Å, and O–H = 2021 © The Japan Society for Analytical Chemistry