Synthesis And Properties Of Chiral Dimeric Liquid Crystals And Chromophoric Aza Crown Ethers

The synthesis,characterization and mesomorphic properties of new dimerliquid crystalline compounds D-mn and their derivatives D2F-mn based on4-(trans-4-alkyl cyclohexyl)benzoic acid and cholesterol are described in this thesis. The cholesterol and 4-(trans-4-alkyl cyclohexyl)benzoic acid derivatives have been connected with different length spacers give 40 new dimerliquid crystals. The starting material substituted cyclohexyl benzoic acid was prepared from substituted phenyl ethanones by bromoform reactions. Ph enyl ethanones were synthesized using acyl chloride, cyclohexene and benze ne as starting materials by Dabrowski method. And another starting materialsubstituted benzoic acid derivatives were obtained from 4-alkyl-cyclohexano ne and substituted bromo-benzene by a general procedure. The mesogenic b ehavior has been studied using differential scanning calo rimetor(DSC)and p olarizing microscope(PM).For the dimers having C₆ spacer the only chiral n ematic(N*) mesophase were observed with broad transition temperature rang e and these compounds show a weak odd-even effect depending on the par ity of terminal alkyl substituent. For the dimers having 2,6-diflouro benzen e ring the lower clean point were found, probably because the introdution of fluoro broadened the dimeter of molecule.Several aza-18-crown-6 ethers having substituted troponyl have been sy nthesized by condensation reaction of aza-18-crown-6 ether and 2-methoxy t ropone or its derivatives. These compounds were characterized by ¹H-NMR.Their complexations with a series of metal ions were studied by UV-ViSspectroscopy and the complex constants of crown ethers were evaluated by spectroscopic titration method. The result showed that 4 new crown ethers all can complex with alkaline metal ions and exibit the best selective comp lexing ability with potassium ion. At the same time, the complexing abilityof l-(4-isopropyl-7-hydroxymethyltropon-2-yl-l-aza-18-crown-6 ether was be tter than that three of other crown ethers by comparing the complexing abil ity ethers with different metal ions (Li\ Na\ Cd2\ Ca2\ Hg2\ Pb2\ K\ Ba24\ NHU+). Finally, it should be pointed out that the synthetic crown ethe r compounds 12, 14 and 16 is readily soluble not only in water but in themost of organic solvents, and can be a useful reagent for analyses. Furthe r studies are in progress.