Synthesis, Characterization And Liquid Crystalline Behavior Of [1,2,3]- Triazole-Based Bidentate Schiff Bases And Related Cu(Ii) Complexes

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dc.contributor.authorHeng, Boon Teck
dc.date.accessioned2018-04-03T06:31:16Z
dc.date.available2018-04-03T06:31:16Z
dc.date.issued2016-10
dc.description.abstractSeven new homologous series of Cu(II) complexes with ligands derived from [1,2,3]-triazole-based bidentate Schiff bases had been successfully synthesized. All the molecular structures were elucidated by elemental analysis and various spectroscopic techniques (UV-visible, FT-IR, 1D, 2D 1H and 13C-NMR). The optical properties and phase transition temperatures were investigated by polarising optical microscope (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The first series is Cu(II) complexes with ligands bearing F, Cl, Br and I atoms as terminal substituent or without substituent. This is notable that fluorosubstituted Cu(II) complexes (C14H29 and C16H33) showed enantiotropic N phase which was absent in their corresponding ligands. X-ray diffraction studies had suggested the alkyl chain self-ordering of SmA and SmC phases in complexes with even parity C14H29 to C18H33. In second series, the effects due to the presence of two terminal flexible chains in ligands had been investigated. X-ray diffraction studies had substantiated the emerging of SmC phase in all ligands and complexes with tilt angle of 37.2-39.5o. This study revealed that the existence of two terminal flexible chains at both sides of ligands could prevent the change in aspect ratio through complexation. The third series is the Cu(II) complexes containing halogenated ligands with three rings system instead of the four rings system in first and second series. The ligands with fluoro and iodo-substituent showed non-stable SmA phase. The ultimate Cu(II) complexes show stable SmA phase. This indicated the important of Cu(II) ion in enhancing the colinearity and molecular anisotropic of ligands. Comparison studies discovered the introduction of an extra aromatic ring could also lead to the stabilization of mesophase. The ligands and complexes in fourth series comprised either bromine atom as terminal substituent or an additional terminal nhexadecyloxy flexible chain. All the ligands are enantiotropic but their corresponding Cu(II) complexes were non-mesomorphic. Comparison studies with ligands and complexes in third series showed that the various location of ortho-hydroxyl group could greatly affect the thermal and mesomorphic behavior. In the fifth series, all the ligands and complexes demonstrated the similar mesomorphic behaviour. This finding further supported the concept as mentioned in second series whereby the aspect ratio will not be affected by complexation due to the presence of two terminal flexible chains in ligands. The sixth series is the complexes with dimesogenic ligands containing cholesterly moiety. The ligands with dodecanoate chain exhibited enantiotropic N* and SmC* phase while the other members exhibited SmC* only. This is worth to mention that all Cu(II) complexes exhibited SmA* phase which was not observed in their respective ligands. This suggested that a new molecular architecture had achieved through the formation of Cu(II) complexes. The final series had molecular structures that are approximately analogous to the aforementioned series but all the ligands and complexes in this series were incorporated with ferroceny moiety instead of the cholesteryl moiety. All the ligands prepared in the final series are non-mesomorphic. However, all their respective Cu(II) complexes showed enantiotropic SmC and SmA phases. The comparison studies had further evidenced the suppression of mesophase by the repulsive effect in between the L-shaped ligands.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/5511
dc.publisherUniversiti Sains Malaysiaen_US
dc.subjectSeven new homologous seriesen_US
dc.subjectof Cu(II) complexesen_US
dc.titleSynthesis, Characterization And Liquid Crystalline Behavior Of [1,2,3]- Triazole-Based Bidentate Schiff Bases And Related Cu(Ii) Complexesen_US
dc.typeThesisen_US
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