二芐環庚烯衍生之螺旋烯在光學開關和電致發光二極元件的應用

李泰瑋(Tai-Wei Li)

指導教授 ： 陳建添

國立臺灣師範大學/理學院/化學系/碩士(2000年)

摘要

中文摘要
螺旋烯類化合物的結構由於上、下盤發光集團的立體障礙而造成不共平面特性。而此類化合物於基態吸收能量而躍遷至激發態之時，位於連結上下盤的雙鍵部份會形成雙自由基狀態，而此雙自由基激發態欲回到基態釋放能量的方式有兩種：一、 吸收能量後，所形成的雙自由基部分，由於雙鍵特性已消失，能量可由分子轉動形成另一異構物而釋放，形成另一異構物。二、所吸收的能量由於轉動能障較大而趨向由放光方式回到基態。而本論文所採取的兩種系統，第一種為上盤以二芐環庚烯酮為基本骨架而下盤採用單一苯環C(2)具L-menthol及(1R, 2S)-2-(1-Methyl-1-phenyl-ethyl)-cyclohexanol光學輔助基合成的螺旋烯類化合物。L-menthol合成的螺旋烯前驅物：環硫化合物，其非鏡像超越值( diasteriomeric excess, de value)只有16 %，且無法直接以管柱層析法加以分離，而以銅粉加熱去硫所得相對應的螺旋烯化合物de值只有20 %，但以(1R, 2S)-2-(1-Methyl-1-phenyl-ethyl)-cyclohexanol光學輔助基合成的環硫化合物de值有34%，且兩種非鏡像異構物能以管柱層析法加以分離，而得到純的兩種異構物，並以X-ray確定其立體結構絕對組態(minor: (R)-pro-(M))，再配合HPLC沖堤順序及CD掌性激發子(exciton chirality)的關係來判別類似結構化合物立體化學(後沖提出者為(R)-pro-(M))，而此類環硫化合物在分離後，以六甲基磷醯胺在0℃下進行的去硫反應也可分別得到近乎diastereomeric pure的螺旋烯，並也能配合HPLC沖堤順序及CD掌性激發子(exciton chirality)的關係來判斷螺旋烯絕對立體化學。而對於此類螺旋烯化合物，我們也進行了其光化學行為及光學開關的探討。
而本實驗室在發展各種不同類型的螺旋烯化合物，研究其光物理行為時發現當改變不同上下盤結構時會有明顯不同系統區分，上述上盤以二芐環庚烯酮為基本骨架者為第一種系統，而本論文另一系統為上盤為二芐環庚酮以及下盤為β-naphthol-flavone的螺旋烯類化合物即屬第二種系統，其能量釋放方式較接近於第二種系統，我們利用結構上的差別，能使得第二種系統的吸收光譜到達可見光範圍(λmax = 358 nm in n-Hexane)，而其放射波長更可達到接近綠光範圍(λmax = 478nm in n-Hexane)，我們利用此特性將其應用到有機電致發光二極體元件(OLED)的應用上。配合循環伏安法我們可得知此類化合物能階及能階差(HOMO = -5.29e.v，LUMO = -2.21e.v)，在增加下盤共軛性及上盤結構C(10)，C(11)位置上增加甲氧基取代方面加強了放光效果，但無預期的加大Stokes Shift的效應。對於此類分子的設計仍有極大空間，而此類化合物對於OLED的主、客發光體的應用上本實驗室為第一個例子，相信對於此領域新型材料的開發將有所幫助。

關鍵字

二芐環庚烯

並列摘要

Abstract
The triarylethenes synthesized adopt helical shapes(ie. helicenes) due to the steric overlap of symmetrical upper-part(ie dibezosuberene or dibenzosuberane) and the unsymmetrical lower part (e.g a.-tetralone at (C2) substituted chiral auxilary or b-naphthol-flavone). The chirality in these inherently pseudoenatiomeric alkenes, was denoted as M or P for left- or right-handed helical handness. When the steric overcrowded alkenes were excited to the singlet excited states, the double bond connecting both parts would exhibits diradical character. It has been documented that the relaxation of the transition state to the ground state proceeds through two ways: Route I, planarization around the diradical single bond with overcomes the torsional and ring strain to a perpendecular excited state enroute to another photostationary isomer. Route II, the energy relaxation is another phenomena often refer to a general term fluorescenct emission procedure. We have so far examined two systems adopted here, the first system consists of dibenzosuberene upper part and a.-tetralone (C2) substituted with L-menthyl and (1R,2S)-2-(1-methyl-1-phenyl-ethyl)-cyclohexy esterl lower part. The de values of L-menthyl based episulfide is 16%, and we can not separate the two diastereomers by flash column chromatography. The de values of Cu-desulfuration helicene of L-menthyl type is 20%. However, we treat another chiral auxilary: (1R, 2S)-2-(1-Methyl-1-phenyl-ethyl)-cyclohexanol, the de values of the episulfide is 34%, and we can get diastereomeric pured episulfides. We demonstrated the absolute configuration by X-ray diffraction. By correlating the retention order in chiral HPLC and CD exciton chirality, we can construct a rule of absolute stereochemistry. The separated episulfides could be treated more mild desulfurized process by HMPT in ice bath. The absolute configuration of helicenes after desulfuration by HMPT is almost diastereomeric pure, and we also construct the rule in determining the absolute stereochemistry. The last work of this system is the study of photochemistry if the helicenes are suitable for optical switches.
The other system consists of dibenzosuberane upper part and b-naphthyl-flavone lower part . The energy relaxation of this system we suggested it to be a fluorescence process by the forward works( Route II). We using the difference in energy relaxation route to design the structure based on DBS and b-naphthyl-flavone helicenes. The absorption band λmax = 358 nm ( in n-Hexane ) and the emission bandλmax = 478nm ( in n-Hexane ). The Stokes shift are 120nm. We applied the compounds to the OLED ,and the properties of EL and PL are almost the same( DBS or DBS(MeO)2/PVK(dopant/host)). From the results of cyclic voltammetry and absorption spectrum, we can calculate the energy levels of the helicences( HOMO = -5.92 e.v, LUMO = -2.21e.v). The C(10), C(11) dimethoxy substituted helicence enhanced the quantum yield, but the red shift does not matcht our expectation. This is the first time using this type helicences acted as OLED dopant and host materials. We believed it would be helpful for designing new OLED materials.

並列關鍵字

dibenzosuberene

參考文獻

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