Research Theme

Structure Control of Supramolecular Complexes by External Stimulus-Responsive

External Stimulus-Responsive Supramolecular Structures

A double-threaded dimer bearing a long substituent part and a large stopper group has been prepared and showed the conformational change with increased solvent polarity.

Tsukagoshi, S.; Miyawaki, A.; Takashima, Y.; Yamaguchi, H.; Harada, A.
Contraction of Supramolecular Double-Threaded Dimer Formed by alpha-Cyclodextrin with a Long Alkyl Chain
Org. Lett. 2007, 9 (6), 1053-1055.

We prepared a stilbene bis(β-CD) dimer and controlled its trans-cis conformation by photoirradiation in aqueous solution. With a ditopic adamantyl guest molecule, in trans conformation, it formed dimer or small supramolecular assemblies (oligomers), whereas in cis conformation, supramolecular linear polymer with high molecular weight were observed. The control of the structure of the supramolecular polymers by an external stimulus may open the way to various applications.

Kuad, P.; Miyawaki, A.; Takashima, Y.; Yamaguchi, H.; Harada, A.
External Stimulus-Responsive Supramolecular Structures Formed by a Stilbene Cyclodextrin Dimer
J. Am. Chem. Soc. 2007, 129 (42), 12630-12631.

We have succeeded in controlling formation of a double threaded dimer and that of non-threaded supramolecular self-assembly consisting of stilbene amide α-CD by photoirradiation as shown in Figure 4. First, we thought that 3-trans-Sti-α-CD would form a supramolecular polymer, and then 3-cis-Sti-α-CD would decompose it after photoirradiation. The facts are contrary to what we expected. Formations of these supramolecular complexes might be due to p-p stacking interactions between stilbene amide groups. These interactions are presumed to inhibit the formation of a supramolecular polymer. Instead, it created more interesting supramolecular system, in other words, "Switching between supramolecular dimer and non-threaded supramolecular self-assembly". The unit of α-CD and the cis-stilbene group play an important role to form supramolecular assembly as a hydrophilic and hydrophobic part, respectively. These interaction and environment promote the p-p stacking of the cis-stilbene group and affect cooperatively the formation of the supramolecular assembly.

Yamauchi, K.; Takashima, Y.; Hashidzume, A.; Yamaguchi, H.; Harada, A.
Switching between Supramolecular Dimer and Non-Threaded Supramolecular Self-Assembly of Stilbene Amide alpha-Cyclodextrin by Photoirradiation
J. Am. Chem. Soc. 2008, 130 (15), 5024-5025.