| Summary: | 碩士 === 國立中央大學 === 化學學系 === 104 === 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.
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