本篇論文主要包含具有quinoxaline結構之有機液晶。所有化合物經由1H-NMR、13C-NMR、元素分析以鑑定其結構及純度，液晶相性質則是利用偏光顯微鏡(POM)來觀測相種類及熱差式掃描分析儀(DSC)測量相變化時之溫度與熱焓值，也藉由氫譜的訊號位移去探討分子內雜環的推拉電子性質，並進一步與UV—可見光光譜的訊號位移相互佐證，最後以變溫粉末X光繞射儀確認相的種類及單晶X光繞射得到的單晶數據去探討其分子的作用力與排列。 在本篇論文中，以分子中心的quinoxaline分別接上長碳鏈、帶有imine的基團或benzoxazole雜環去合成系列一的1a、1b、1c及1d四種化合物，並對其液晶相、排列還有UV—可見光吸收所造成的影響。而在系列二將探討以quinoxaline為中心但具有不同imine位向的Schiff Base化合物1c及2，我們發現由於分子連結基部份的C = N位置差異，產生不同種類的氫鍵進而對相變化、液晶性質、推拉電子效應及分子排列造成影響。系列三則是將quinoxaline雜環各別與isoxazole、pyrazole及oxadiazole做連結即化合物3a、3b與3c，探討此三者雜環對液晶相的影響以及不同雜環下推拉電子特性對其吸收光譜的差異討論。;In this three series , new compounds were prepared and their mesomorphic properties were investigated. All organic derivatives were characterized by 1H-NMR and 13C-NMR spectroscopy. The mesomorphic behavior of these compounds were investigated by polarized optical microscopy (POM), differential scanning calorimetry (DSC), and powder X-ray diffraction (XRD) measurement. In series I, rod-like molecules based on quinoxalines 1a was synthesized. Furthermore, the similar compounds containing an imine moiety 1b 、 1c and its cyclized product, Benzoxazoles 1d are also described and their mesomorphic properties examined. In series II, heterocyclic quinoxaline Schiff Base 2 were prepared, characterized and their mesomorphic properties investigated. These compounds 1c and 2 are in fact geometric isomers in which an inime moiety (e.g. –C=N) is inversely incorporated into quinoxaline, leading to an opposite local dipole. Intra- and intermolecular H-bonds were found in both crystals. In series III, Both Quinoxaline and three different kinds of five membered rings contained molecules, 3a、3b and 3c, were synthesized. All compounds are rod-lke mesogens. Due to the different five-membered ring, the electron-withdrawing abilities were examined by NMR spectrum.
