•Isophthalamide based on 5-(2-phenylethynyl)isophathalilc acid was prepared.•The corresponding receptors showed UV–vis and fluorescence changes with guests.•The skeleton can be applied to various receptors.We have successfully prepared 5-(2-phenylethynyl)isophathalilc acid as a signaling unit and the corresponding derivatives for an anion receptor 2 and a barbiturate receptor 4. Receptor 2 showed characteristic UV–vis changes and dramatic fluorescence quenching upon the addition of anions and receptor 4 showed UV–vis and an OFF-ON fluorescence changes upon the addition of dibutylbarbituric acid based on the diphenylethyne moiety.Download high-res image (152KB)Download full-size image

A cyclic bisurea derivative 2a has been successfully prepared from the corresponding diamine and diisocyanate in the presence of tetrabutylammonium chloride as a template. A more soluble cyclic bisurea 2b has also been prepared by introduction of sterically bulky tert-butyl groups. X-ray crystal analyses of [2a·Cl]− and [2b·Cl]− revealed that overall structure was saddle like and the chloride anion was located in the center of the cavity. The bound chloride anion was hydrogen bonded by four N–H of urea groups and weakly hydrogen bonded by four 1-C–H of naphthyl groups, respectively. After removal of the bound chloride anions of [2b·Cl]− with silver nitrate, two different X-ray crystals of free 2b were obtained; one was intermolecular hydrogen bonded shrunken structure and the other was extended structure. Receptor 2b showed large binding ability for Cl–, however, the selectivity for Cl– against basic anions, such as AcO– and F–, has been insufficient. In aqueous MeCN, the association constant of 2b for Cl– was reduced but still large, and the selectivity for hydrophobic Cl– was greatly improved. In this solvent, 2b also selectively recognized alkaline metal chloride salts. Therefore, cyclic bisurea 2b is highly selective and effective Cl– selective receptor.

Di(1-pyrenyl)silane and di(1-pyrenyl)methane derivatives showed unprecedented intramolecular excimer emission in polar organic solvents such as DMSO and the ratio of excimer/monomer emissions strongly depends on the dielectric constants of the solvents.

Novel fluororeceptors 2 and 3 based on tetraamide bearing 1-isoquinolyl and 2-quinolyl moieties were designed and synthesized. Highly selective and significant changes in the UV–vis and fluorescence spectra of the receptors upon the addition of H2PO4– were found. In particular, receptor 3 bearing 2-quinolyl groups shows selective and nearly perfect quenching by H2PO4–, whereas 3 shows small or no fluorescence changes by another anion.

Two silanediol derivatives bearing 9-anthryl (2) and 1-pyrenyl (3) groups have been developed for fluorescence detection of anions. Receptor 3 showed favorable ratiometric response by fluorescence spectroscopy upon the addition of biologically relevant anions, such as acetate and dihydrogen phosphate in acetonitrile.

Two trimethylsilyl groups were introduced at 5- and 5′-positions of 2,2′-binaphthalene to improve the solubility of 2,2′-binaphthalene-based receptors. The X-ray crystallographic analysis revealed the twisted structure of 2 in the solid state. The solubility of 2 was moderately improved by 3.1-fold comparing with mother skeleton 1. As a practical example of 2, receptor 8 bearing two aza-15-crown-5 moieties was prepared and the selective binding of 8 with Ba2+ can be observed by the formation of sandwich-like complex, which shows no prevention of binding ability of the receptor by introduction of the bulky substituents.

As a novel chromofluorophore, 9,9′-dimethyl-2,2′-bianthracene 3 has been successfully synthesized by reductive coupling of 2-chloro-9-methylanthracene. Absorbance and fluorescence maxima of 3 can be shifted to visible-region comparing to the former 2,2′-binaphthyl-based receptors. Receptor 2 bearing aza-15-crown-5 moieties via methylene spacer provides selective UV–vis and fluorescence responses for Ba2+ due to the restriction of the conformational change through the formation of an intramolecular sandwich-complex by two azacrown ethers, resulting in the presence of Ba2+ that can be detected by naked eye in aqueous acetonitrile.

Anion recognition properties of d-ribose-based receptors α- and β-1 were measured by 1H NMR in CDCl3 and MeCN-d3. Receptor β-1 showed effective binding with anions by cooperative hydrogen bonds of cis-diol. The anomeric isomer α-1 is a less effective anion receptor which has similar cis-diol as a recognition site, indicating that the stereo configuration of the anomeric position is of significant influence on the anion recognition ability.