Synthesis and characterization of novel photoluminescent materials containing conjugated- rings with pyridine and alkoxy-substituted lateral groups
Dr. Hong-Cheu Lin
|關鍵字:||氫鍵液晶;有機發光;吡啶;共軛環;hydrogen bonding liquid crystal;organic light emitting;pyridine;conjugated ring|
本實驗主要是以McMurry coupling reaction、Heck coupling reaction合成出一系列含吡啶之芳香共軛環的螢光材料，所有化合物經由H1-NMR、C13-NMR 和元素分析加以鑑定其結構與純度，再與不同的質子予體酸製備成氫鍵錯合物。在熱性質方面，以熱重分析儀(TGA)得知熱裂解溫度(Td)為259℃~413℃。由熱微差掃瞄分析儀(DSC)與偏光顯微鏡(POM)觀察出合配製成的氫鍵錯合物中，只有PBBPOC4- ONA、PBBPOC8 -ONA顯現了向列型液晶的性質，其他的錯合物並沒有液晶相。化合物的螢光性質則由紫外光可見光光譜儀（UV-Vis）和螢光分光光譜儀測得，化合物在極稀(10-5M)的二氯甲烷溶劑中所得到的最大吸收波長範圍為388nm~448nm;最大螢光（PL）放射波長為454nm ~500nm，化合物PBBBrOC4、PBBBrOC8為發藍綠光材料，PBBPMe、PBBPOMe、PBBPOC4、PBBPOC8為發綠光材料，量子效率為35％∼70％。當配置氫鍵錯合物時所取用的酸pH值越強，越容易形成氫鍵錯合物，由於拉電子效應變強，分子LUMO變低，energy band gap就變窄，所以酸度最強的THDA配成氫鍵錯合物後，其造成紅位移的現象最為明顯。循環伏安法(CV)測得不可逆氧化電位，得知本系列化合物HOMO位於5.30 eV ~ 5.82 eV。由於還原電位不明顯，經由λmax onset推算得知LUMO位於2.89 eV ~3.58 eV。在液晶性質和發光特性相結合的偏極化實驗中，成功發現共軛螢光分子在液晶相(配位後)中可發出具有方向性的偏極化光，且Polarization ratio 約有1.43倍的差距。|
Synthesis and characterization of novel photoluminescent materials containing conjugated-rings with pyridine and alkoxy-substituted lateral groups Graduate student: Boon-Seng Ng Advisor:Dr. Hong-Cheu Lin Department of Materials Science and Engineering National Chiao Tung University Abstract A series of novel photoluminescent materials with conjugated aromatic segment including end-capping pyridine and substituted alkoxy group were synthesized successfully via Mcmurry, and Heck reaction. Hydrogen bonding complexes were obtained from the mixing of these photolumines -cent compounds with different proton donors containing carboxylic acids groups in THF/CH2Cl2. The thermal properties of these materials were measured by TGA. The decomposition temperature at 5% weight loss (Td) of all compounds ranged from 259℃~413℃. DSC and POM claimed that most of these compounds have no mesogenic phase except PBBPOC4-ONA and OBBPOC8-ONA. The optical properties of these materials were measured by UV-Vis and PL (photoluminescence) spectroscopic studies. These compounds exhibited maximum absorption in the range of 388nm ~448nm in diluted CH2Cl2. They emitted blue-green to green fluorescence around 456~500nm in CH2Cl2. The quantum efficiency of them were ranged from 35%~70% comparing to coumarin 6. For a good formation of Hydrogen-bonding complexes, the highly acidic proton donor should be used . The energy band gap was shortened once the Hydrogen- bonding complexes were formed. According to the PL spectra, the complexes whose contains THDA showing the most apparent red-shifted emission due to its lowest pka value. The CV showed that the HOMO and LUMO of these compounds were located at 5.30 eV ~ 5.82 eV and 2.89 eV ~3.58 eV respectively. The polarization measurement showed the existence of the polarized light and the polarization ratio is about 1.43 .