Synthesis and spectroscopic characterization of chiral biphenyl-cholesterol gels.
Synthesis and spectroscopic characterization of chiral biphenyl-cholesterol gels.
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DOI：
10.1021/la503954b
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发表时间：
2014-11
期刊：
影响因子：
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通讯作者：
H. Geiger;Melissa Lamson;Daniel J Galka
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文献类型：
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作者：
H. Geiger;Melissa Lamson;Daniel J Galka
报道了4-（3-胆固醇氧羰基丙氧基）联苯（BO_4-chol）、4-（7-胆固醇氧羰基庚氧基）联苯（BO_8-chol）和4，4 ′-双（7-胆固醇氧羰基庚氧基）联苯（BBO_8-chol）的合成。这些胶凝剂在正辛醇中形成1%和2%（w/w）的稳定凝胶。由单一胆固醇胶凝剂（BO 4-chol和BO 8-chol）形成的凝胶表现出比由双胆固醇胶凝剂BO 8-chol（96 - 98 ° C）获得的凝胶更低的相变温度（Tg）（62 - 65，68 - 69 ° C）。所有三种胶凝剂在正辛醇中形成手性凝胶，如通过诱导圆二色性（ICD）光谱所观察到的。通过圆二色谱（CD）、吸收光谱和荧光光谱研究了两个胆固醇部分与一个胆固醇单元通过柔性链连接到联苯分子上的效果，以及链长对这三种新型胶凝剂的胶凝能力的影响。从BO_4-chol和BO_8-chol得到的凝胶显示具有相反手性的双相圆二色性光谱。在室温下，BO 8-chol和BBO 8-chol凝胶的ICD光谱均显示出正ICD带，随后是负带。然而，虽然B08-chol凝胶ICD吸收随着温度升高而同等地降低，但是BB08-chol凝胶显示出在50 ° C和60 ° C之间的科顿效应带的反转，直到在相变温度以上完全消失。利用扫描电镜对干凝胶的形貌进行了研究。XRD数据和分子模拟的基础上，我们提出了形成的有机凝胶剂聚集体的包装模式。
The synthesis of 4-(3-cholesteroxycarbonylpropyloxy)biphenyl (BO4-chol), 4-(7-cholesteroxycarbonylheptyloxy)biphenyl (BO8-chol), and 4,4'-bis(7-cholesteroxycarbonyl heptyloxy)biphenyl (BBO8-chol) is reported. These gelators form 1% and 2% (w/w) stable gels in n-octanol. The gels formed from single cholesterol gelators (BO4-chol and BO8-chol) exhibit lower phase transition temperatures (Tg) (62-65, 68-69 °C) than the gel obtained from the bischolesterol gelator BBO8-chol (96-98 °C). All three gelators form chiral gels in n-octanol as observed by induced circular dichroism (ICD) spectroscopy. The effect of two cholesterol moieties versus one cholesterol unit linked to a biphenyl molecule by a flexible chain, and the effect of the chain length on the gelation ability of these three novel gelators was investigated by circular dichroism (CD), absorption, and fluorescence spectroscopies. The gels obtained from BO4-chol and BO8-chol exhibit biphasic circular dichroism spectra with opposite chirality. The ICD spectra of both BO8-chol and BBO8-chol gels show a positive ICD band followed by a negative band at room temperature. However, while BO8-chol gel ICD absorptions decrease equally as temperature increases, BBO8-chol gel shows an inversion of the Cotton effect bands between 50 and 60 °C until completely disappearing above the phase transition temperature. SEM was used for the investigation of the morphology of the xerogels. On the basis of XRD data and molecular modeling, we propose packing modes for the formation of the organogelator aggregates.