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| 題名: | 含pyrazole, 1,3,4 - thiadiazole雜環以及BF2-chelated 結構之桿狀液晶性質探討 |
| 作者: | 許圓君;Hsu, Yuan-Chun |
| 貢獻者: | 化學學系 |
| 關鍵詞: | 液晶;mesogen;liquid crystal |
| 日期: | 2018-07-10 |
| 上傳時間: | 2018-08-31 11:32:05 (UTC+8) |
| 出版者: | 國立中央大學 |
| 摘要: | 本篇論文主要分為兩個系列，在系列一中成功合成以pyrazole及1,3,4-thiadiazole雜環為中心硬核之1a-b與2為配位基，與boron difluoride (BF2) 形成錯合物1a-BF2、1b-BF2及2-BF2。藉由引入以雜環系統為主結構之配位基再接上boron difluoride (BF2) 成為硼錯合物來觀察其對液晶形為表現的影響。研究發現中心雜環為pyrazole的化合物1a-b具有SmA或SmC的桿狀液晶相而將雜環換成1,3,4-thiadiazole的化合物2則具有N、SmA或SmC相且液晶相範圍較1a-b廣，再來螯合上BF2的化合物1a-BF2、1b-BF2則無液晶相生成，而化合物2-BF2具有SmA相。從培養出的化合物1a (n = 5)、2 (n = 6) 以及2 (n = 10) 單晶探討分子排列以及其分子間之作用力並以XRD實驗結果推論其在液晶相之排列情形。化合物1a-b、2以及2-BF2 (長碳鏈總碳數相同) 以UV可見光吸收光譜以及螢光放光光譜來探討其光學性質，由結果得知化合物2-BF2的放光波長較2的波長藍移且量子產率也較高。另外，化合物2受excited state intramolecular proton transfer (ESIPT) effect 影響，其Stokes shift大於化合物2-BF2。
系列二成功合成出以淳洋學長之benzothiazole結構，化合物3為中心雜環作為配位基並與BF2進行螯合形成硼錯合物3-BF2 (n = 8, 10, 12)，經POM與XRD粉末繞射實驗之結果判斷3-BF2 (n = 8) 具有N相以及SmC相，而3-BF2 (n = 10-12) 則具有SmC相桿狀液晶。從培養出的化合物3-BF2單晶與淳洋學長培養的化合物3單晶比較並探討分子排列以及其分子間之作用力。另外化合物3 (n = 12)以及3-BF2 (n = 12) 以UV可見光吸收光譜以及螢光放光光譜來探討其光學性質，由結果得知化合物3-BF2的吸放光波長較3的波長紅移且量子產率也較高。
;Nowadays more and more liquid-crystalline compounds containing five-membered hetrocycles are the subject of many investigations. These heterocyclic structures generally incorporated of such electronegative atoms (S, O or N atom) often resulted in a reduced or lowering symmetry for the overall molecules or/and a stronger polar induction. Quite a few examples, including pyrazoles, isoxazoles, 1,3,4-oxadiazoles, 1,3,4-thiadiazoles and others have been prepared and investigated in our group. Most of them formed smectic phases whereas, only a few of them exhibited columnar phases.
Additionally, complexes containing boron difluoride (BF2) have been paid much attention in the past few years. Many of boron difluoride complexes have been investigated as fluorescent materials, thus showing potential applications in many fields; such as biological imaging, molecular probes, electroluminescent devices, photosensitizers and others. However, they seldom reported as mesogenic applcations.
In series I, a new series of symmetry pyrazole or 1,3,4-thiadiazole compounds 1a-b and 2, and mono-(boron difluoride) complexes 1a-BF2, 1b-BF2 and 2-BF2 derived from 1a-b and 2 was synthesized and their mesomorphic and optical properties were also investigated. The single crystals of mesogenic 1a (n = 5), 2 (n = 6), 2 (n = 10) were obtained, and its single crystal and molecular structures were resolved. The results suggested that compounds 1a-b, 2 and 2-BF2 exhibited enantiotropic smectic mesophases and 1a-BF2, 1b-BF2 were nonmesogenic. The luminescent emission showed that ligand 2 exhibited a larger Stokes shift than complexes 2-BF2 beacause of excited state intramolecular proton transfer (ESIPT) effect.
In series II, a new series of mono-(boron difluoride) complexes 3-BF2 derived from substituted benzothiazole Schiff base 3 were reported, and their mesomorphic and optical properties were also investigated. The single crystals of mesogenic boron complexes 3-BF2 (n = 8) was obtained, and its single crystal and molecular structures were resolved. The results suggested that mono-(boron difluoride) complexes 3-BF2 exhibited enantiotropic smectic mesophases. The luminescent emission showed that in the excited state, the position of the maximum appears to be dependent on the chelation of BF2 as visible red shifts from 524 nm to 565 nm of the emission bands are detected in compounds 3 and 3-BF2. |
| 顯示於類別: | [化學研究所] 博碩士論文
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