Artificial ribofuranoside receptors were designed and synthesized. The design of the polypyridinemacrocyclic receptors was based on the multipoint hydrogen bond complementarity between the receptors and methyl /3-D-ribofuranoside. The binding affinity of the receptors for the ribofuranoside in CDCl3 was very high (up to Ka = 5.2 x lo3 M-'), so that even native ribose was extracted by them into such nonpolar solvents. Selective extraction of ribose by the receptors was observed: the extractabilities, or affinities to the receptors of various pentoses and hexoses decreased in the following order: ribose > deoxyribose r lyxose xylose > fructose > arabinose > glucose mannose = galactose. The selectivity is governed by the OH direction and the whole size of the sugars as well as their shapes. Furthermore, fluorescence emission of the receptors was largely enhanced in the presence of methyl /3-D-ribofuranoside or ribose, and the degree for the fluorescence enhancement by the addition of various sugars was almost compatible with that of the extractabilities. The polypyridine-macrocycles represent rationally designed multifunctional artificial receptors for ribofuranosides.

We developed a new class of water-soluble cyclophanes, pyrenophanes, capable of encompassing a neutral cavity, in which the hydrophobic area is constructed by aligning two flat polynuclear aromatic rings parallel at an appropriate space that could interpose just one layer of aromatic plane. The height, depth, and width of the cavity in an open conformation of the pyrenophane are 0.46, 0.95, and 1.31 nm, respectively, i.e., the area of this cavity is so large that even porphirin compounds might be incorporated. In the fluorescence spectra, the pyrenophanes showed only excimer-emission, reflecting the existence of two proximal pyrene rings. Treatment of the pyrenophanes with anionic and cationic aromatic compounds revealed the formation of complexes in the UV and fluorescence spectra, suggesting that the binding affinities of the pyrenophanes for aromatic compounds were mainly governed by hydrophobic and/or π-stacking interactions. The macrocyclic structures of the pyrenophanes were found to be indispensable for the complexation.

We newly prepared para- and meta-linked alkynylpyrene oligomers and examined their photophysical properties. Oligomerization of monomeric building blocks was performed by CuI-promoted oxidative coupling reaction. The resulting oligomers mainly consist of 2-mer to 6-mer that were assigned on the basis of MALDI-TOF mass spectra, and the 2-mer, 3-mer, and 4-mer were isolated and fully characterized. From their absorption and fluorescence spectra, the para-linked oligomers were found to be somewhat pi-conjugated compared with meta-linked ones, and the fluorescence quantum yields decreased with increasing oligomer length (Phif = 0.79-0.55).