| 摘要: | 在系列一中成功合成出以substituted tetraketonates 1-5為配位基，與boron difluoride (BF2) 形成錯合物1-BF25-BF2，其中化合物1-BF2與2-BF2並無液晶相產生，而化合物3-BF25-BF2 (n = 10, 12, 14) 因達適合的軟端硬核比例，經由偏光紋理圖與powder X-ray diffraction實驗結果判定為Colh盤狀液晶。化合物1-5, 1-BF25-BF2 ( n = 12) 以UV可見光光譜、螢光光譜及固態螢光光譜探討該分子的光學性質，從結果可得知增加推電子的烷氧基數目與從tetraketonates形成含雙BF2錯合物時皆使得最大放光波長紅移。化合物3-BF25-BF2為目前少見含雙BF2結構之盤狀液晶，且為室溫液晶。
在系列二中成功合成出以苯環為中心硬核且含有兩個pyrazole及isoxazole 之對稱同雜環衍生化合物1a-6b，本實驗藉由引入雜環系統、改變分子軟硬端比、改變位相、引入氫氧基來觀察以上因素對化合物液晶行為的影響。經由偏光紋理圖與powder X-ray diffraction實驗結果能判定含有pyrazole的化合物2a、3a及含有isoxazole的化合物4b、5b皆有Colh盤狀液晶的出現，且在4b (n = 10, 12) 只有單向型液晶發現。而含有氫氧基6a則有SmX相發現。最後置入氫氧基的6a、6b的OH的氫鍵使分子間作用力增加，使其澄清點溫度較沒置入氫氧基1a、1b的高。化合物1a-6a ( n = 12) 以UV可見光光譜、螢光光譜譜探討該分子的光學性質，可以發現擁有最長共軛的5a其吸收吸收波長最紅位移，而置入氫氧基的6a螢光波長較1a藍位移。
在系列三中成功合成出以苯環為中心硬核且含有三個pyrazole及isoxazole 之同雜環衍生化合物7a、7b，可以發現含有pyrazole的化合物7a有較強的分子間氫鍵作用力因此澄清點較7b高。而在7a中可以觀察到黏滯性大、流動性差的SmX相；搭配變溫IR，藉由升降溫peak變化，可發現從固態到液態分子間氫鍵作用力變化。
;Complexes or adducts containing boron difluoride (BF2) have been paid much attention during the past years. Many known boron difluoride complexes, widely investigated as fluorescent materials showed potential applications in many areas; such as biological imaging, molecular probes, electroluminescent devices, photosensitizers and others. However, only a few examples were reported among mesogenic applications.
In the first part, five new series of bis(boron difluoride) complexes 1-BF25-BF2 derived from substituted tetraketonates 1-5 were reported, and their mesomorphic and optical properties were also investigated. Results appeared that bis(BF2) complexes 1-BF2、2-BF2 were nonmesogenic and 3-BF25-BF2 (n = 10, 12, 14) exhibited enantiotropic columnar mesophases. A value of Ncell = 3.143.76 within a column slice of 9.0 Å thick was obtained for compound 3-BF25-BF2, indicating that a single discshaped molecule was stacked within columns in Colh phases. Bis(BF2) complexes 1-BF25-BF2 (n = 12) possess a pronounced greenyellow emission in solution at room temperature and possess a pronounced orangered emission in solid at room temperature. The luminescent emission also showed a strong dependence with structural moiety incorporated. To our best knowledge, there are rare examples of columnar bis(BF2) complexes.
Nowadays more and more liquid-crystalline compounds containing five-membered heterocycles are the subject of much investigation. 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, isoxazole, 1,3,4-oxaziazoles, 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.
In the second series, a system of twin mesogens containing pyrazoles and isoxazoles was synthesized and characterized by 1H NMR, 13C NMR, Mass spectrometry and Elementary anaylysis. In this experiment, the effect of the above factors on the liquid crystal behavior of the compound was observed by introducing a heterocyclic system, changing the ratio of the hard and soft terminals, changing the patern, and introducing a hydroxyl group. The results of POM and powder X-ray diffraction experiments indicate that compounds 2a, 3a, 4b and 5b show the Colh liquid crystals.And the presence of hydroxyl 6a has SmX phase found.In UV absorption spectra, the reddish shift of 5a is due to its longest conjugation length
In the third series,the heterocyclic derivative 7a, 7b with a benzene ring as the central hard core and three pyrazole and isoxazole compounds were successfully synthesized, and 7a clean point is higher than 7b, because 7a has strong intermolecular hydrogen bonding force.In the 7a, the SmX phase can be observed. With the variable temperature IR, the change of the hydrogen bonding force from the solid state to the liquid state can be found by the change of the peak. |
