1 Introduction Synthesis, elucidation of crystal structures, and investigation of physical properties of new liquid crys- tals are important for studying the relationship between molecular structures and mesophases (1-4). We have synthesized liquid crystals with tropone core such as 2- benzoyloxytropone (5), 2-benzoylaminotropone (6), 5- phenyltropone (7), bitropone (8,9), N,N’-bis(tropon-2- yl)piperazine (3), tropon-4-yl benzoate (10). In some cases, troponoid derivatives were mesomorphic although the corresponding benzenoid derivatives were not. These are due to the large dipole moment of the tropone ring. Recently in order to obtain the informa- tion about intermolecular interactions controlling mesophases, the crystal structures of troponoid liquid crystals such as 5-butoxy-2-(4-methoxybenzoylamino)- tropone (6), N,N’-bis(5-decanyloxytropon-2-yl)-piper- azine (3), 2,2’-dioctyloxy-5,5’-bitropone (8), and 5- nitro-2-(4-octyloxybenzoylamino)tropone (4) have been elucidated by X-ray crystallographic analysis. For example, the single crystal structure of N, N’-bis(5- decanyloxytropon-2-yl)piperazine (3) was closely relat- ed to the layer structure of the mesophases whereas that of the non-mesomorphic ones was not. In this paper, the synthesis, crystal structure, and mesomorphic properties of new troponoid liquid crystals (1a-d) with a bis(tro- pon-2-yl)-4,4’-azobisbenzoate were investigated. 2 Experimental 2･1 Analysis Elemental analyses were performed at the elemental analysis laboratory of Kyushu University. The melting points were obtained using a Yanagimoto micro-melt- ing-point apparatus and are uncorrected. The NMR spectra were recorded using JEOL Lambda 400 spec- trometer and solutions in CDCl 3 at room temperature; the chemical shifts are expressed in d units. The mass spectra were measured with JEOL JMS-700 spectrome- 179 JOS Journal of Oleo Science ISSN 1345-8957 print / ISSN 1347-3352 online http://jos.jstage.jst.go.jp/en/ 1 Institute for Materials Chemistry and Engineering, Kyushu University (Kasuga-koen, Kasuga, Fukuoka 816-8580, JAPAN) 2 Department of Applied Chemistry, Faculty of Engineering, Oita University (Dannoharu, Oita 870-1192, JAPAN) 3 Department of Chemistry, Institute of Organic Chemistry, Martin-Luther-University Halle-Wittenberg (Kurt-Mothes Strasse 2, D-06120 Halle/Saale, Germany) Kanji KUBO 1＊ , Akira MORI 1 , Seiji UJIIE 2 and Carsten TSCHIERSKE 3 Edited by K. Kobayashi, Musashi Inst. Tech., and accepted October 28, 2004 (received for review August 23, 2004) Synthesis, Crystal Structure, and Mesomorphic Properties of Liquid Crystals with a Bis(tropon-2-yl)-4,4’-azobisbenzoate Core ＊ Correspondence to: Kanji KUBO, Institute for Materials Chemistry and Engineering, Kyushu University, Kasuga-koen, Kasuga, Fukuoka 816- 8580, JAPAN E-mail: kubo-k@cm.kyushu-u.ac.jp JOURNAL OF OLEO SCIENCE Copyright ©2005 by Japan Oil Chemists’ Society J. Oleo Sci., Vol. 54, No. 3, 179-183 (2005) Abstract: New troponoid liquid crystals with bis(tropon-2-yl)-4,4’-azobisbenzoate core were prepared. Compound (1) had enantiotropic nematic and/or smectic C phase. The crystals of 1a had intermolecular p-p interactions between azobenzene planes and between tropone rings. The nematic liquid crystal (1a) did not form any layer structure in crystal state. X-ray diffraction studies revealed that 1c and 1d formed the tilted layers in the smectic C phase. Key words: tropone, azobenzene, liquid crystal, nematic phase, crystal structure