Kawano Shin-Ichiro, Tamaru Shun-Ichi, Fujita Norifumi, Shinkai Seiji
Department of Chemistry & Biochemisry, Graduate School of Engineering, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
Chemistry. 2004 Jan 23;10(2):343-51. doi: 10.1002/chem.200305042.
Sugar-appended porphyrins (1 a-e) with monosaccharide groups at their periphery have been rationally designed for a new class of gelating reagents. A few of these compounds have the tendancy to form one-dimensional aggregates stable enough to show successful gelation ability for DMF-alcohol mixed solvents. The aggregation mode in the specific columnar super structures has been evaluated in detail by UV-visible spectrometry (UV/Vis), circular dichroism (CD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). All UV-visible spectra of sugar-appended porphyrinic gels obtained from 1 a-c exhibit Soret band absorptions, which shift to lower wavelength and are significantly broadened. This phenomenon indicates that these porphyrin cores strongly interact with each other in an H-aggregate fashion, which drives the generation of a one-dimensional porphyrin-stacking array. The CD spectra of the organogels from 1 a and 1 b, which are in anomers, exhibit an almost symmetric pattern, whereas the gel from 1 c gives a completely different pattern. This implies that the gel fibrils wind themselves in a right- or left-handed fashion; this reflects chirality in the specific molecular structure of the gelators. The results from SEM for the gel fibrils are in good agreement with the CD patterns. The gel fibrils in 1 a possess left-handed helicity, whereas those in 1 b wind themselves right-handedly. Macroscopic helical morphology reflects the microscopic structure well at a molecular level, which gives structural variety of the gel fibrils, which can be defined by the sugar library. Inorganic conversion of the organic helical fibrils by a sol-gel transcription process successfully gives the helical-silica structures, which finely inherit the organic morphology. A striking observation is that a unimolecular porphyrin-stacking array is also transcribed into silica fibers when the optimized sol-gel reaction conditions are selected. A sugar-based organic-fiber library in porphyrinic gels thus provides a variety of inorganic materials through the sol-gel transcription process.
在其外围带有单糖基团的糖基化卟啉（1 a - e）已被合理设计用于一类新型的胶凝剂。其中一些化合物倾向于形成一维聚集体，其稳定性足以使其对DMF - 醇混合溶剂表现出成功的胶凝能力。通过紫外 - 可见光谱法（UV / Vis）、圆二色性（CD）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）对特定柱状超结构中的聚集模式进行了详细评估。从1 a - c获得的糖基化卟啉凝胶的所有紫外 - 可见光谱均显示出Soret带吸收，该吸收峰向较低波长移动并显著变宽。这种现象表明这些卟啉核以H - 聚集体的方式强烈相互作用，从而驱动一维卟啉堆积阵列的生成。1 a和1 b的有机凝胶的CD光谱（它们是异头物）呈现出几乎对称的模式，而1 c的凝胶给出了完全不同的模式。这意味着凝胶原纤维以右手或左手方式缠绕；这反映了胶凝剂特定分子结构中的手性。凝胶原纤维的SEM结果与CD模式高度一致。1 a中的凝胶原纤维具有左手螺旋性，而1 b中的则以右手方式缠绕。宏观螺旋形态在分子水平上很好地反映了微观结构，这赋予了凝胶原纤维结构多样性，这可以由糖库来定义。通过溶胶 - 凝胶转录过程对有机螺旋原纤维进行无机转化成功得到了螺旋二氧化硅结构，其精细地继承了有机形态。一个引人注目的观察结果是，当选择优化的溶胶 - 凝胶反应条件时，单分子卟啉堆积阵列也被转录到二氧化硅纤维中。因此，卟啉凝胶中的基于糖的有机纤维库通过溶胶 - 凝胶转录过程提供了多种无机材料。
