壹、以掌性二芐環庚烷為骨架之構形控制螺旋烯光學開關之研究; 貳、以二芐環庚烯為骨架之掌性螺旋烯光學開關及其偶氮苯衍生物結合的雙調控光學開關之研究

Abstract

我們成功的合成以C2對稱(10R,11R)-雙庚氧甲基取代之掌性二苄環庚烷 (DBS) 為上盤骨架，下盤骨架為7-Br--tetralin之構形控制螺旋烯光學開關1a；利用波長290及330 nm的光分別照射(P)-1a的己烷溶液，可測得P/M’-form的比例由<1/>99至90/10；當以波長310 nm的光照射1a的己烷溶液後，可使P/M’-form的比例切換至50/50。利用波長290、310及330 nm的光照射(P)-1a所誘導生成的膽固醇相液晶進行光異構化反應，可以調控膽固醇相液晶的螺距大小並分別得到(-)、off及(+)的訊號，成為具有三元 (ternary) 邏輯概念的記憶材料。 我們也發展以二苄環庚烯 (DBE) 為上盤骨架，並且在上盤C3、C7位置分別引入偶氮苯側鏈，下盤骨架為具有薄荷醇衍生物之掌性輔助基的螺旋烯雙調控光學開關1i；當以己烷為溶劑時，利用波長380或480 nm的光照射，可以進行化合物1i之高選擇性光致變色偶氮苯的順反異構化(E,E-1i/Z,Z-1i, 19/81 to >99/<1)；以波長254及300 nm搭配480或380 nm的光進行掌致變色螺旋烯的光異構化反應，可以得到高選擇性的螺旋掌性反轉 (P/M, 92/8 to 3/97, 88/12 to 6/94)。利用上述波長的光對化合物1i所誘導生成的膽固醇相液晶進行光異構化反應，可以使化合物1i的四個半穩定態之間互相切換，達成調控膽固醇相液晶的螺距大小及相對的螺旋掌性變化。

We have documented a conformation-controlled optical switch of helicene 1a bearing C2-symmetric, (10R,11R)-diheptoxymethyl-dibenzosuberane (DBS) top template and a common 7-bromo--tetralin based bottom fragment. Photoisomerization of the diastereomerically pure (P)-1a at 290 or 330 nm in hexanes can lead the ratio of P/M’-form from<1/>99 to 90/10. Irradiation of either (P)-1a or (M’)-1a at 310 nm results in a pss with equal ammounts of both helicenes. Upon irradiation of the cholesteric mesophase induced by (P)-1a at 290, 330 or 310 nm result in photo-modulation of the pitch, reversal and turn-off of the helical handedness, and with a switch memory of ternary logic. We have also documented a dual-mode optical switch 1i by appending two azobenzene units onto the C3 and C7 positions of a dibenzosuberene (DBE)-based helicenebearing an 8-naphthylmenthol-derived chiral ester. The highly diastereoselective photochromic switchings of azobenzene moieties of 1i in hexanes can be effected upon irradiation at 380 or 480 nm (E,E-1i/Z,Z-1i, 19/81 to >99/<1). Irradiation at 254 or 300 nm collocated with a 480 or 380 nm excitation results in highly diastereoselective chirochromic switchings of helicene moiety of 1i (P/M, 92/8 to 3/97, 88/12 to 6/94). Photoisomerization of the dopant (1i) by judicious irradiation at these selected wavelengths can induce the cholesteric mesophase with modulable pitches and complementary handedness. It’s a new dual-mode optical switch possessing four different metastable states by combining helicene and bis-azobenzene in close proximity.