具雙偶氮苯衍生物之二芐環庚烷為骨架的螺旋烯類化合物在光學切換和自組裝的研究與探討 Diazobenzene-derivated helicenes of dual mode and further discussion of the completely developed helicene in the photoswitch in our lab and the performance of the behavior of photochemistry.

Date
2008
Authors
李翊瑋
Yi-Wei, Lee
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Abstract
本篇論文合成了具雙光學切換模式之雙偶氮苯衍生物取代之螺旋烯化合物,並與本實驗室發展完整之螺旋烯系統在光學切換及光化學行為上的表現作進一步的討論。掌性雙偶氮苯衍生物取代之螺旋烯分子1具有兩個光學切換部分,一個為掌致變色(chirochromic)螺旋烯分子之 (P) - (M) form 間切換;另一個為光致變色(photochromic)偶氮苯分子之 cis 與 trans 間切換。螺旋烯分子於基態吸收能量而躍遷至激發時,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;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;偶氮苯分子部份則是利用氮氮雙鍵經由照光後,在 cis 與 trans 間進行切換。本論文藉由照射波長 280 nm 的光,可得到幾乎是單一 M 形式的非鏡像立體異構物(P/M = 4/96),接著照射波長 365 nm 的光4小時,可達到(trans/cis = 67/32)光異構化的選擇性;而照射波長 435 nm 的光7小時,則可得到幾乎是單一trans 形式的非鏡像異構物(trans/cis = 99/1)。 在液晶分子摻雜的部份,我們嘗試改變不同的濃度及升溫或降溫過程,透過偏光顯微鏡觀察其液晶紋理圖,其中包含了指紋狀(fingerprint)、扇片狀(fan-like)、多角形(polygonal)等膽固醇相液晶。我們亦利用不同波長的光照射經加入配製樣品後的楔型槽,歸納出(P) - (M) form 間切換造成螺距改變較順反式之間的異構化為大。利用照射不同波長的光,可以選擇性異構化各官能基,微調整個分子立體化學結構,改變膽固醇相液晶排列的方式。就我們所知,我們的系統是第一個結合螺旋烯分子與偶氮苯衍生物的例子,相信未來在液晶光學開關的發展與應用上是深具潛力的。
This essay contains the diazobenzene-derivated helicenes of dual mode and further discussion of the completely developed helicene in the photoswitch in our lab and the performance of the behavior of photochemistry. Chiral diazobenzene-derivated helicene 1 contaons 2 parts of photoswitch. One is the switch in the (P)-(M) form of chirochromic helicene; the other one is the switch between the cis of photochromic azobenzene and the transformation. When helicene excites to the excrtacl state because it absorb the energy from at the ground state, the double bond at connect up and down point will transform to a diradical state. And this diradical excited state will goes back to the ground state to release the energy by 2 methods: First of all, the diradical part formed after absorb the energy may release from molecular rotate to another isonner due to the disappearance of double bond characteristic. Secondly, the absoured energy intends to go back to the ground state by by light because the rotation energy gap is bigger. The part of azobenzene, on the other hand, uses illuminated N-N double bond switching between cis and transformation. This essay may get diastereomers (P/M = 4/96) in a form very much closed to a single M. Then, it illuminates the light with a wavelength of 365 nm which lasts 4 hours and may reach (trans/cis = 67/32) photoselectivity; when it illuminates the light with a wavelength of 435 nm for 7 hours, may gain disatereomers (trans/cis = 99/1) in a form very much closed to single trans. At the part of liquid crystal dopond , we tried to change different condensity and the process of heating and cooling.We observe its texture through partial optical microscope . And it contains cholestic liquid crystal such as fingerprint shape, fan-like shape, and polygonal shape. We may also the light with different wavelength illuminates wedge cell added with sample packing to conclude that the pitch change caused by the switch of the (P)-(M) form is greater than the isomer between cis-trans form. By illuminating the light with different wavelength, we may selectively isomerize each funtional group, slightly orgnize the stereochmical structure of the entire molecule, and change the way of the arranfement of cholectic liquid crystal. So far as we know, our system is the first example which combines helicene and azobenzene-derivated. And we believe that it has great potential at the development and the application of liquid crystal and photoswitch in the future.
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Keywords
光學切換, photoswitch
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