氫鍵型錯合物與雙元體藍相液晶之研究暨膽固醇液晶材料於金屬離子檢測之應用

Abstract

含氫鍵型彎曲狀分子之錯合物藉由各式砒碇(T)與苯酸(D)衍伸物間之超分子作用力製備，並比較其類似結構錯合物之物理與化學特性，更進一步將氫鍵型彎曲狀液晶分子與相似之共價鍵型分子相互比較。氫鍵型雙元體分子藉由相同莫耳數之砒碇與苯酸衍伸物製備而得，而氫鍵型錯合物藉由不同莫耳數之砒碇與苯酸衍伸物製備而得。藉由導入氫鍵於彎曲狀液晶分子之不同位置，可以影響分子產生液晶相之溫寬，當氫鍵於彎曲狀液晶分子後具有寬廣之膽固醇相時，也有助於含氫鍵型彎曲狀液晶分子之錯合物誘導與穩定藍相。於含氫鍵型彎曲狀液晶分子之錯合物中，錯合物之藍相液晶溫寬會受到砒碇與苯酸衍伸物之莫耳比例、氫鍵型彎曲狀液晶分子烷基鏈長度、苯酸衍伸物之側向氟取代基與旋光中心所影響。當氫鍵受體PIIIC9與氫鍵予體AIIF*以莫耳數比為三比七混合時具有最寬廣之藍相一溫寬(12.0 °C)，此錯合物即為最佳化後之藍相液晶錯合物。因為相較於含氫鍵型彎曲狀液晶分子之錯合物，含共價鍵型彎曲狀液晶分子之混合物只具有較窄的藍相三溫寬，因此氫鍵的導入確實有利於藍相一的生成與安定化。 具有寬廣藍相溫寬(13.7°C)之棒狀與氫鍵彎曲狀分子結合之不對稱結構超分子液晶雙元體C/D首次被成功設計與合成，此超分子液晶雙元體之結構具有雙旋光中心分為於氫鍵受體與予體上，此外分子不具有側向極性取代基(氟基)。藉由分子模擬結果可以得知，在超分子液晶雙元體中分子結構具有較大的雙軸參數(W1/W2 ≥ 3.2)與適當的螺旋扭曲功率(4.2-4.8 μm-1)可以有效的誘導藍相一之生成並穩定之。在超分子液晶雙元體中，氫鍵於分子結構上之位置與旋光中心於分子結構上之位置與數目皆影響分子之彎曲角度、雙軸參數與偶極矩。此外側向氟取代不利於藍相液晶於超分子液晶雙元體之生成，最佳化之藍相一於具有適當的彎曲角度與較大雙軸參數，但較小之偶極矩與無側向氟取代基之分子PIII*/AII*。 本研究之膽固醇液晶金屬離子感測器藉由混合市售膽固醇液晶混合物與高濃度(約30 mol%)之新穎探針分子(3EOCB)製備，本新穎探針分子具有三-環氧乙烷與氰基之雙探頭結構，此膽固醇液晶金屬離子感測器對於三價鐵離子(Fe3+)具有非常高的選擇性。本膽固醇液晶金屬離子感測器利用肉眼可觀測之顏色變化進而分辨金屬離子種類，在偵測大多數金屬離子時本膽固醇液晶金屬離子感測器之顏色為由藍綠色(509 nm)變化為藍色(ca. 484-468 nm)。由於協調機制的不同，此膽固醇液晶金屬離子感測器偵測三價鐵離子時顏色由藍綠色變化為紅色(ca. 663 nm)，且在偵測鉀離子(K+)時顏色由藍綠色變化為綠色(ca. 541 nm)。在相同金屬離子價電子數下，本膽固醇液晶金屬離子感測器之顏色藍位移變化量與金屬離子之離子半徑有關。本研究內容也對於第一次發現膽固醇液晶金屬離子感測器偵測不同種類金屬離子同時產生紅位移與藍位移之現象進行說明，並發現此現象為新穎探針分子之雙探頭皆會與金屬離子產生鍵結作用所導致。並發現當膽固醇液晶載體(E7)具有可與金屬離子鍵結之官能基(氰基)時，本膽固醇液晶金屬離子感測器偵測三價鐵離子之紅位移顏色變化量可藉由協同效應大幅提升。

Various hydrogen-bonded (H-bonded) bent-core liquid crystal complexes consisting of pyridyl and benzoic acid derivatives were synthesized and compared with their covalent analogues in this study. The molar ratios of pyridyl and benzoic acid derivatives could be tuned to form various H-bonded liquid crystal (LC) diads (with 1 : 1 molar ratio of H-acceptors T and H-donors D) and complexes (with different molar ratios of T and D). By insertion of H-bonds into different positions of bent-core supramolecules, the mesophasic properties of H-bonded bent-core LC complexes were optimized, which could facilitate the most suitable LC components and compositions to be utilized in H-bonded blue phase (BP) LC complexes. In BPLC complexes, the molar ratios, alkyl chain lengths, the lateral fluoro-substitution and the chiral center of H-bonded bent-core supramolecules would affect the temperature ranges of BPs. Accordingly, H-bonded bent-core complex PIIIC9/AIIF* (3/7 mol mol1) displayed the widest BPI range of ΔTBPI = 12.0 °C at the correspondent H-acceptor T = PIIIC9 and H-donor D = AIIF*. Since the covalentbonded bent-core mixture only had narrow ranges of BPIII, we could summarize that the introduction of H-bonds into the bent-core center effectively stabilizes the BPs and easier induces the BPI. The first series of liquid crystalline supramolecular diads C/D containing asymmetric rod-like and H-bonded bent-core mesogens were designed and synthesised, among which supramolecular diad PIII*/AII* with two chiral centers on both H-accepter/H-donor and non-lateral fluoride substitution possessed a wide blue phase I (BPI) range of 13.7°C. According to the molecular modeling, a large biaxial parameter (W1/W2 ≥ 3.2) and an appropriate HTP value (4.2-4.8 μm-1) are the most important factors to stabilize the double twisted cylinder structure (i.e., BPI) in supramolecular diads. Moreover, the bent angles, biaxial parameters and dipole moments of supramolecular diads are mainly affected by the locations and numbers of H-bonds and chiral centers. Not only larger bent angles and biaxial parameters but also smaller dipole moments and HTP values were obtained by removing the lateral fluoride substitution on supramolecular diads to achieve the BPI of PIII*/AII* (without lateral fluoride substitution). We develop novel cholesteric liquid crystal sensor (CLCS) materials containing commercially available cholesteric liquid crystal (CLC) hosts with a saturated concentration (ca. 30 mol%) of a simple sensor probe (3EOCB) possessing bi-functional moieties (tri-ethylene oxide and CN), which reveal high selectivities towards particular metal ion, i.e., including ferric (Fe3+) ion. Generally, as mixed with most metal ions the CLCS materials show blue-shifted reflections, which demonstrate color changes from blue-green (509 nm) to blue (ca. 484-468 nm) observed by naked-eyes. Due to different coordination mechanisms of particular metal ions with 3EOCB, only ferric (Fe3+) and potassium (K+) ions illustrate red-shifted color changes, i.e., from blue-green (509 nm) to red (ca. 663 nm) and green (ca. 541 nm), respectively. Overall, the blue-shifted reflection wavelengths of CLCSs towards most metal ions were proportional to the ionic radius of metal ions with the same valence number. The special binding mechanisms of tri-ethylene oxide and CN moieties in probe 3EOCB towards metal ions are proposed to explain the special phenomena of both blue- and red-shifted (i.e., dual-wavelength-shifted) reflection color changes in the CLCSs for the first time of metal ion detections ever been observed by naked eyes. In addition, the largest red-shifted reflection wavelength of CLCS with specific LC host E7 are ascribed by the synergism of 3EOCB and E7 for ferric (Fe3+) ion detection.