Akihiko Ueno

Excimer formation in inclusion complexes of modified cyclodextrins

Abstract A β-cyclodextrin derivative, which possesses a polyether chain with a naphthyl moiety at its end, shows excimer emission in its concentrated solutions. The excimer was suggested to be formed between the two naphthyl moieties included in the long cylindrical cavity of the cyclodextrin dimer.

Tight inclusion of an acid guest into the cavity of cyclodextrin bearing an amino moiety in dimethyl sulfoxide

Abstract Circular dichroism measurements show that β-cyclodextrin with an amino moiety has a strong binding ability for ferrocenecarboxylic acid in dimethyl sulfoxide via an acid-base interaction.

Photoresponsive binding ability of azobenzene-appended γ-cyclodextrin

Abstract Azobenzene-appended γ-cyclodextrin, which can form 1:1 complexes with a variety of guests in its trans form, exhibits promoted binding ability for (−)-borneol and (+)-fenchone by photoirradiation.

Exciton coupling, excimer emission and unique binding behavior of γ-cyclodextrin substituted by two naphthyl residues

Abstract A modified γ-cyclodextrin substituted by two naphthyl residues, which exhibits exciton coupling band and excimer emission, binds various guests by changing the location of the naphthyl residues.

Exciton coupling, intramolecular self-complexation, and host-guest complex formation of 6A,6X-bis-(anthracene-9-carbonyl) derivatives of cyclomalto-octaose

Abstract The four regioisomers of 6 A ,6 X -bis(anthracene-9-carbonyl)cyclomalto-octaose ( 1-4 , X = B-E) exist in solution in aqueous 10% ethylene glycol as intramolecular complexes, in which two anthracene moieties are included in the cavity of cyclomalto-octaose. Spectroscopic data suggest that the arrangement of the two anthracene rings is nearest to face-to-face in 4 and the most remote in 2 . The c.d. spectra of the regioisomers reveal excition coupling bands in the 1 B b region with the patterns of R -helicity for 1, 2 , and 4 , and S -helicity for 3 . The regioisomers changed the intensities and shapes of the exciton coupling bands on complexation with l -borneol. The host-guest association constants were in the order 4 3 1 2 , indicating that the intramolecular complexes stabilized by the face-to-face interaction of the anthracene moieties are difficult to convert into intermolecular complexes.

Photo-excitable membranes. Photoinduced membrane potential changes across poly(vinyl chloride) membranes doped with azobenzene-modified crown ethers

The membrane potentials across a plasticized poly(vinyl chloride)(PVC) membrane entrapping azobenzene-modified 15-crown-5 (1) or 18-crown-6 (2) were measured under conditions of u.v. and visible light irradiation. Irradiation induced significant potential changes across the membranes, of a magnitude depending on the cation species, on the ionic concentration in the solution, and on the crown ether content in the membrane. The sign of the potential shift was dependent upon the direction from which the membrane was irradiated. The results are explained in terms of surface potential changes at both surfaces of the membrane, associated with the release of cations from the membrane phase into the solution upon irradiation.

Binding and catalytic behavior of modified ?-cyclodextrins

Modified γ-cyclodextrins appended by an aromatic moiety show unique binding behavior, including a guest molecule together with the appended moiety in their γ-cyclodextrin cavities. Excimer formation, photoresponsive binding, association with (s-cyc lodextr in and enhanced catalytic activity have been explained on this basis.

Inclusion and Reaction Chemistry of Two Anthracene-Appended γ-Cyclodextrins

The anthracene moieties of regioisomers of 6A,6X-bis(anthracene-9-carbonyl)-γ-cyclodextrins undergo photodimerization, affording a trans photodimer for AC, AD, and AE isomers and a cis photodimer for the AB isomer. The photodimers of the AD and AE isomers were stable, but those of AB and AC were unstable, returning to the original anthracene monomers. The dissociation of the photodimers was suggested to be due to the inherent instability of the cis photodimer of the AB isomer and the strain-rich nature of the trans photodimer of the AC isomer. The photodimerization followed by hydrolysis of 6A,6X-bis-(anthracene-1-carbonyl)-γ-cyclodextrins afforded four photodimers of 1-anthracenecarboxylic acid, the relative yields of the photodimers being controlled by the locations of the anthracene moieties in the regioisomers. These results demonstrate that the γ-cyclodextrin template method is useful to make chemical reactions proceed stereoselectively as well as to produce new photochrome systems.