Cyclodextrin (CD) based supramolecular complexes have been prepared using a stilbene bis(β-CD) dimer and a ditopic adamantyl guest. The conformation of the stilbene bis(β-CD) dimer in aqueous solutions could be photochemically controlled. The ROESY spectra of the β-CD dimer with the adamantyl dimer showed NOE between the protons of adamantyl moieties and the inner protons of the CD. When the host cyclodextrin dimer was in trans conformation, supramolecular dimers or small assemblies are formed in solutions, whereas in its cis conformation supramolecular linear polymers with high molecular weight were observed. Thus the structure of the supramolecular polymers could be controlled by an external stimulus.

A pseudo[1]rotaxane formed by a flexible cyclodextrin (CD) derivative (1-R) with a bulky end group has been investigated on kinetic quantitation. 1-Rs have the cinnamamide moiety as a guest and a bulky end group (R) as a rate-determining moiety of the threading process. The R groups play an important role for the formation of pseudo[1]rotaxane, and kinetics of the self-inclusion process was found to be controlled by the size and shapes of the R groups. 1-Ad and 1-Me derivatives, which have an adamantyl and methyl end group, respectively, formed self-inclusion complexes by threading of the arm moiety with a conformational conversion of altrose from (1)C(4) form to (4)C(1) form. Flexibility of the altro-alpha-CD cavity resulted in an induced fit (from (1)C(4) to (4)C(1)) to the arm moiety, and introducing a bulky end group allowed the stability of this pseudo[1]rotaxane to be enhanced.

Poly[2]rotaxane and supramolecular assembly have been prepared by modified cyclodextrins bearing an adamantyl group in an aqueous medium.

An alkyl altro-alpha-CD dimer was converted to the pseudo[1]rotaxane dimer through tumbling of the altropyranose unit of altro-alpha-CD in D(2)O. The tumbling of the altropyranose unit was found to be a rotational vibration with 1.18 x 10(-3) s(-1) at 293 K. The activation free energy (DeltaG(double dagger)(288K)) for the conformational change from an alkyl altro-alpha-CD dimer to pseudo[1]rotaxane dimer was 88.0 kJ mol(-1), which corresponds to the breakage of the hydrogen bond network for the tumbling of an altropyranose unit.

A double-threaded dimer bearing a long substituent part and a large stopper group has been prepared and showed a conformational change with increased solvent polarity. [structure: see text]