Helical ribbon aggregate composed of a crown-appended cholesterol derivative which acts as an amphiphilic gelator of organic solvents and as a template for chiral silica transcription
Helical ribbon aggregate composed of a crown-appended cholesterol derivative which acts as an amphiphilic gelator of organic solvents and as a template for chiral silica transcription
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DOI：
10.1021/ja010508h
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发表时间：
2001-09-12
影响因子：
15
通讯作者：
Shinkai, S
中科院分区：
文献类型：
--
作者：
Jung, JH;Kobayashi, H;Shinkai, S
合成了一种新的冠醚修饰的胆固醇基有机凝胶剂1，它具有两个胆固醇骨架作为手性聚集体形成位点，两个氨基作为酸性质子结合位点，一个冠醚部分作为阳离子结合位点，并在有机溶剂中评价了它的凝胶化能力，在1.0wt%以下，它可以凝胶化乙酸、乙腈、丙酮、乙醇、正丁醇、正己醇、DMSO和DMF，表明1作为各种有机溶剂的通用胶凝剂。为了表征有机凝胶系统中的聚集模式，我们观察了乙酸凝胶1的CD光谱。在CD光谱中，λ（θ =0）值出现在353 nm处，这与吸收最大值λ（max）= 353 nm相同。第一个柯顿效应的正号表明偶氮苯发色团的偶极矩倾向于顺时针方向取向。非常令人惊讶的是，1 +乙酸凝胶的TEM图像产生螺旋带和管状结构。在凝胶相中使用1进行正硅酸乙酯的溶胶-凝胶聚合。从1 +乙酸凝胶获得的二氧化硅显示出具有1700-1800-nm节距的螺旋带和具有类似于560-nm外径的二氧化硅的管状结构。据可以认识到，所有的螺旋性具有右手螺旋基序。由于激子耦合带的有机凝胶也显示R（右手）螺旋，我们认为微观螺旋反映了宏观螺旋。
New crown-appended cholesterol-based organogelator 1, which has two cholesterol skeletons as a chiral aggregate-forming site, two amino groups as an acidic proton-binding site, and one crown moiety as a cation-binding site, was synthesized, and the gelation ability was evaluated in organic solvents, It can gelate acetic acid, acetonitrile, acetone, ethanol, 1-butanol, 1-hexanol, DMSO, and DMF under 1.0 wt %, indicating that 1 acts as a versatile gelator of various organic solvents. To characterize the aggregation mode in the organogel system, we observed a CD spectrum of the acetic acid gel 1. In the CD spectrum, the lambda (theta =0) value appears at 353 nm, which is the same as the absorption maximum lambda (max) = 353 nm. The positive sign for the first Cotton effect indicates that the dipole moments of azobenzene chromophores tend to orient in a clockwise direction. Very surprisingly, the TEM images of the 1 + acetic acid gel resulted in the helical ribbon and the tubular structures. Sol-gel polymerization of tetraethoxysilane was carried out using 1 in the gel phase. The silica obtained from the 1 + acetic acid gel showed the helical ribbon with 1700-1800-nm pitches and the tubular structure of the silica with similar to 560-nm outer diameter. As far as can be recognized, all the helicity possesses a right-handed helical motif. Since the exciton-coupling band of the organogel also shows R (right-handed) helicity, we consider that a microscopic helicity is reflected by a macroscopic helicity.