Crystal Structure of <i>N,N</i>′-Bis(5-butoxytropon-2-yl)piperazine

Abstract

37The elucidation of crystal structures and investigations of the physical properties of liquid crystals are important for studying the relationship between molecular structures and mesophases. 1,2 X-ray crystallographic analysis plays an important role for obtaining information about intermolecular interactions controlling the mesophases. Recently, we prepared liquid crystals with a N,N′-bis(tropon-2-yl)piperazine core. 3-5N,N′-Bis(5-alkoxytropon-2-yl)piperazines had a phase sequence of crystals-smectic C phase-isotropic for n = 8 -16, while N,N′-bis(5-buthoxytropon-2-yl)piperazine (1) (Fig. 1) was not mesomorphic. The crystal structure of 1 has not yet been reported. We now report on the structure of 1 with the aim to contribute to a deeper understanding of the relationships between the mesomorphic properties and the molecular packing in the crystal structure.Compound (1) was prepared by the condensation of piperazine and 2-methoxy-5-butoxytropone in an ethanol-toluene solution, as reported in a previous paper. Single crystals of 1 were grown in a mixture of chloroform-ethyl acetate (1:1 v/v) at room temperature. The data collection and refinement parameters are listed in Table 1. The H atoms were positioned with the idealized geometry, and were refined to be isotropic (Uiso(H) = 1.2Ueq(C)) using a riding model with C-H = 0.95 Å for aromatic H atoms C-H = 0.99 Å for methylene H atoms, and C-H = 0.98 Å for methyl H atoms. The selected bond distances and torsion angles are collected in Table 2.An ORTEP drawing of molecule of 1 is shown in Fig. 2. The molecules of 1 sit on a center of symmetry with the two tropone ring systems in an anti conformation; the piperazine ring has a normal chair conformation. The angle between the least-squares tropone plane (defined by O1/C1/C2/C3/C4/C5/C6/C7) and the 2016 © The Japan Society for Analytical Chemistry † To whom correspondence should be addressed. E-mail: kubo@lst.hokkai-s-u.ac.jp Crystal Structure of N,N′-Bis(5-butoxytropon-2-yl)piperazineKanji KUBO,* † Emi YAMAMOTO,** Taisuke MATSUMOTO,*** and Akira MORI***