Hierarchical self-assembly of chiral complementary hydrogen-bond networks in water: Reconstitution of supramolecular membranes

被引:167
作者
Kawasaki, T [1 ]
Tokuhiro, M [1 ]
Kimizuka, N [1 ]
Kunitake, T [1 ]
机构
[1] Kyushu Univ, Dept Appl Chem, Fac Engn, Higashi Ku, Fukuoka 8128581, Japan
关键词
D O I
10.1021/ja010035e
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Spontaneous formation of complementary hydrogen-bond pairs and their hierarchical self-assembly (reconstitution) into chiral supramolecular membranes are achieved in water by mixing amphiphilic pairs of glutamate-derived melamine 6 and ammonium-derivatized azobenzene cyanuric acid 4. Electron microscopy is used to observe formation of helical superstructures, which are distinct from the aggregate structures observed for each of the single components in water. In addition, a spectral blue-shift and induced circular dichroism (ICD) with exciton coupling are observed for the pi-pi* absorption of the azobenzene chromophores. These observations are consistent with the reconstitution of the hydrogen-bond-mediated supramolecular membrane 6-4. Spectral titration experiments indicate the stoichiometric integration of the complementary subunits with an association constant of 1.13 x 10(5) M-1. This value is considerably larger than those reported for the artificial hydrogen-bonding complexes in aqueous media. The remarkable reconstitution efficiency is ascribed to the hydrophobically driven self-organization of the amphiphilic, linear hydrogen-bond networks in water. Molecular structure of the complementary subunits plays an important role in the complexation process since it is restricted by the photoisomerized cis-azobenzene subunit. On the other hand, thermally regenerated trans-isomer 4 undergoes facile complexation with the counterpart 6. The present reconstitution of supramolecular membranes provides the first example of complementary hydrogen-bond-directed formation of soluble, mesoscopic supramolecular assemblies in water.
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页码:6792 / 6800
页数:9
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