Mesogenic Heterocycles Formed by Quinoxalines, Bis–pyrazoles, and Bis–1, 3, 4–Oxadiazoles

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/68095

Title:	Mesogenic Heterocycles Formed by Quinoxalines, Bis–pyrazoles, and Bis–1, 3, 4–Oxadiazoles
Authors:	林冠廷;Lin,Kuan-Ting
Contributors:	化學學系
Keywords:	盤狀液晶;喹喔啉;惡二唑;columnar liquid crystal;quinoxaline;oxadiazole;thiophene;pyrazole;smectic C
Date:	2015-07-15
Issue Date:	2015-09-23 10:44:20 (UTC+8)
Publisher:	國立中央大學
Abstract:	此論文主要分為四個系列，在第一系列中，成功合成及研究兩種不對稱1,3,4oxa(thia)diazoles具有quinoxaline及naphthalene結構1ab和2，我們利用偏光顯微鏡、熱微差掃描分析儀鑑定化合物具液晶性質，同時也藉由TGA鑑定化合物的熱穩定性，再利用X–Ray粉末繞射儀判斷其液晶相為Colh相，並將粉末繞射所得到的數據做理論計算模擬出化合物在液晶相中的堆疊情形，最後我們對化合物的發光性質做探討。　　第二系列中，成功合成及研究四種具有quinoxaline和四種1, 3, 4–oxadiaozles spacer的結構1ad，我們利用偏光顯微鏡、熱微差掃描分析儀，鑑定化合物具液晶性質，同時也藉由TGA鑑定化合物的熱穩定性，再利用X–Ray粉末繞射儀判斷其液晶相為Colh以及ColL相，並將粉末繞射所得到的數據做理論計算模擬出化合物在液晶相中的堆疊情形，最後我們對化合物的發光性質做UV和PL的探討。　　　第三系列中，成功合成及研究三種具有quinoxaline, bisoxazoles, 和bisthiazoles的catenar 液晶結構1ac，我們利用偏光顯微鏡、熱微差掃描分析儀鑑定化合物具有液晶性質，同時也藉由TGA鑑定化合物的熱穩定性，再以X–Ray粉末繞射儀判斷其液晶相為Colh相，並將粉末繞射所得到的數據做理論計算模擬出化合物在液晶相中的堆疊情形，最後我們對化合物的發光性質做探討。　　第四系列中，成功合成及研究具有thiophene, pyrazoles 和1, 3, 4–oxadiazoles的結構1ac，我們利用偏光顯微鏡、熱微差掃描分析儀鑑定化合物具有液晶性質，同時也藉由TGA鑑定化合物的熱穩定性，再以X–Ray粉末繞射儀判斷其液晶相為SmA, SmC和Colh相，並將粉末繞射所得到的數據做理論計算模擬出化合物在液晶相中的堆疊情形，最後我們對化合物的發光性質做UV、PL探討。 ;This thesis is devided into four different series. In series 1, two new structures of unsymmetric 1, 3, 4–oxa(thia)–diazoles 1a–b and 2 containing both quinoxaline and naphthalene moieties were prepared and their mesomorphic properties were investigated. The mesomorphic behavior of compounds 1–2 was studied by DSC analysis and polarized optical microscopy. All compounds 1a and 2 exhibited hexagonal columnar phases (Colh), which were also confirmed by powder XRD diffractometer. Ncell and Rar values equal to 5.23 and 22.73 Å within a slice of 9.0 Å thick were also obtained for 1a (n=16), indicating that a more disc-like structure constructed by two molecules lying side-by-side was correlated in Colh phases. In contrast, all compounds 1b were not mesogenic, and the lack of mesomorphic properties in 1b might be due to their unfavorable conformations. The PL spectra of all compounds 1a, b showed one intense peak at λmax = 509–512 nm, and these photoluminescent emissions originated from quinoxaline moiety. In series 2, four new series of quinoxaline with four kind of 1, 3, 4–oxadiazoles spacer 1a–d were designed and prepared. Their mesomorphic properties were investigated. The mesomorphic behavior of compounds 1a–1d was studied by DSC analysis and polarized optical microscopy. All compounds 1a and 1d exhibited hexagonal columnar phases (Colh), which were also confirmed by powder XRD diffractometer. Ncell values equal to 2.85 and 2.16, Rar values are 20.49 and 22.74 Å within a slice of 9.0 Å thick were also obtained for 1a (n=12) and 1d (n = 12), indicating that a single molecule was packed within the columns in Colh phases. In contrast, all compounds 1c were not mesogenic, and the lack of mesomorphic properties in 1c might be due to their unfavorable conformations. The PL spectra of all compounds 1a–1d showed one intense peak at λmax = 517–529 nm, and these photoluminescent emissions originated from quinoxaline moiety. In series 3, three new materials of catenar liquid crystals 1a–c derived from heterocyclic bisoxazoles and bisthiazoles exhibiting columnar phases were reported. All compounds 1a–c exhibited hexagonal columnar phases, which were also confirmed by powder XRD diffractometer. Compounds 1a have a slightly wider temperature range of columnar phases than those of compounds 1b, which might be attributed to higher core dipole polarized in 1a. A Ncell and Rar value equal to 2.54–2.76 and 19.99–20.45 Å within a slice of 9.0 Å thick were obtained for three derivatives 1a–c (all n = 12), indicating that a single molecule was packed within the columns in Colh phases. All derivatives showed good stabilities at temperature below T = 408.8 C on TGA analysis. The PL spectra of all compounds 1a–c showed one intense peak at λmax = 505–510 nm, and these photoluminescent emissions originated from quinoxaline moiety. In series 4, three new series of multiple heterocyclic compounds 1a–c constructed by bis–pyrazoles, bis–1, 3, 4–oxadiazoles and thiophene exhibiting mesophases were reported. Crystallographic data showed that the crystal 1a (n = 8) is a linear–shaped molecule with a molecular length of ca. 40.57 Å. However, three heterocyclic rings were not coplanar. All compounds 1a formed smectic A/C phases, and all compounds 1c exhibited columnar phases, which were confirmed by powder XRD diffractometer. A Ncell and Rar value equal to 3.91 and 18.29 Å within a slice of 9.0 Å thick were obtained for derivatives 1c (n = 8), indicating that two molecule was correlated within columns in Colh phases. All derivatives showed good stabilities at temperature below T = 383–426 C on TGA. The PL spectra of all compounds 1b–c (n = 8) showed one intense peak at λmax = 418–496 nm, and these photoluminescent emissions originated from 1, 3, 4–oxadiazole moiety.
Appears in Collections:	[Graduate Institute of Chemistry] Electronic Thesis & Dissertation

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