| 摘要: | 本論文研究主要分成三個系列。所有化合物經由1H-NMR、13C-NMR、Mass與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)來觀測相種類及熱微差掃描分析儀(DSC)測量相變化時之溫度與熱焓值，最後以變溫粉末X光繞射儀(XRD)確認相的種類。 系列一：合成出具有benzoxazole環的液晶分子，探討不同碳數(n = 1, 4, 8, 12, 16)及有無OH官能基對液晶相的影響；系列二：利用配位基與不同金屬(Cu, Ni, Pd, Co, Zn)產生配位，結果發現配位方式為平面四邊形的Cu, Ni, Pd錯合物具有液晶相，而配位方式為四面體的Co、Zn則無液晶相。系列三：探討不同取代基對於液晶相生成之影響，實驗發現當取代基為越強拉電子基時為SmA相，而推電子基時為N相，且利用理論計算預測出HOMO及LUMO的電子雲分布，因而推出推拉電子基對energy gap的影響。 Three series of mesogenic compounds were prepared and studied in this thesis. All compounds described were characterized via 1H-NMR, 13C-NMR, mass spectroscopy, and elemental analysis. The mesophases were studied polarized optical microscopy (POM) and differential scanning calorimeter (DSC), and the structures of the mesophases were also confirmed by variable temperature X-ray diffraction experiments. In the first series, a new type of mesogenic compounds derived from heterocyclic benzoxales were prepared and studied. All compounds exhibited nematic or/and smectic phases depending on the carbon length attached. In the second series, numberous metal complexes including copper, palladium, cobalt, zinc and nickel ion coordinated with substituted benzoxales were prepared and their mesomorphic behavior studied. Their mesomorphic properties were dependent on the metal incorported. All Cu2+, Ni2+ and Pd2+ complexes exhibited nematic, or/and smectic plases, however, Zn and Co were crystalline phases. The mesomorphic properties were attributed to the geometries (tetrahedral or square planar) and electronic configuration (paramagnetic or diamagnetic) of the metal ions incorporated. In the third series, the effect of substituent groups on the formation of the mesophases was invistigated. A variety of benzoxale derivatives with a substituent including CN, NO2, Cl, Br, OCF3, F, OCH3 were studied. The data indicated that the formation of the mesophase were strongly dependent on the electronic properties of the substituents. A SmA phase was observed for derivatives with a strong electrondrawing substituent, and a N phase was observed for the derivative with an electrondonating substituent. Electron cloud distribution between HOMH and LUMO precticted by theoretical calculation is studied, and the data showed that there is an energy gap of the electrondrawing and electrondonating substituent. |
