A branched [4]rotaxane containing three switching arms with both secondary ammonium cation and aniline binding sites for threaded crown ethers was prepared. 1H NMR spectroscopy was used to show the translational isomerisation of the [4]rotaxane, and different absorption maxima and the oxidation potential for the [4]rotaxane possessing a 1,3,5-tris(4-aminophenyl)benzene centre were monitored by ultraviolet spectroscopy and electrochemical studies, respectively, as the [4]rotaxane was exposed to encircling dibenzo[24]crown-8 species.

This Letter describes the base- and acid-mediated four-state (partially five-state) translational isomerization of a mixture of two [2]rotaxanes, each containing N-alkylamine and N-arylamine centers as binding sites for threaded crown ethers. Gradual changes in the molecular shuttling of each [2]rotaxane were achieved in response to both the amount and strength of the added acid or base.

This communication describes the base- and acid-induced five-state translational isomerization of a [3]rotaxane containing two pairs of N-arylamine and N-alkylamine centers as binding sites for two dibenzo[24]crown-8 components. Gradual molecular shuttling of this [3]rotaxane is achieved in response to both the amount and strength of the added acid or base.

This Letter describes the formation of pseudo[3]rotaxanes containing calix[4]-bis-crowns, exhibiting a 1,3-alternate conformation and large crown cavities, and secondary ammonium ions. The first and second association constants of pseudo[3]rotaxane formation are moderate (K1 = 175, K2 = 100 M−1) and are higher than that of the corresponding pseudo[2]rotaxane (K = 24 M−1), consisting of a calix[4]-mono-crown and the same secondary ammonium ion.

This paper describes the acid/base-mediated three-state translational isomerization of two [2]rotaxanes, each containing N-alkylaniline and N,N-dialkylamine centers as binding sites for threaded dibenzo[24]crown-8 units. Under neutral conditions, the dialkylamine unit predominantly recognized the crown ether component through cooperative binding of a proton; when both amino units were protonated under acidic conditions, both translational isomers were generated; the addition of a strong base caused aniline–crown ether interactions to dominate. The three states of the [2]rotaxane featuring the 3,5-diphenylaniline terminus in its dumbbell-shaped component were accompanied by distinct absorptive outputs that were detectable using UV spectroscopy.

This Letter describes a series of [2]rotaxanes featuring a 3,5-diphenylaniline terminus in their dumbbell-shaped component and crown ethers as the macrocyclic component, prepared through imine formation and hydrogen bond—guided self-assembly. Electrochemical studies of these [2]rotaxanes revealed that the oxidation potential of the aniline moiety when positioned within the cavity of a crown ether was shifted negatively relative to that of the corresponding dumbbell-shaped compound, and that a crown ether possessing a small cavity and a large number of aromatic rings had a more negative effect on the oxidation potential of the aniline moiety than did a large-cavity crown ether featuring no aromatic rings. UV experiments showed that absorption band of the rotaxanes bearing small crowns shifted to longer wavelengths as compared to those of the rotaxanes having large crowns.

In this study, we investigated the effect of pressure on the formation and decomplexation of [2]pseudorotaxanes. High pressure accelerated the formation of [2]pseudorotaxanes in an aprotic nonpolar solvent (CDCl3/CD3CN) via the slipping approach when using two crown ether/secondary ammonium salt systems: dibenzo[24]crown-8/bis(cyclohexylmethyl)ammonium salt (1a/2a) and tetrabenzo[24]crown-8/dibenzylammonium salt (1b/2b). The influence of pressure on the rate constants for the formation of the [2]pseudorotaxanes 3a and 3b revealed activation volumes (ΔV⧧) of −2.5 and −4.6 cm3 mol−1, respectively, at 303 K and zero pressure. We also investigated the effect of pressure on the decomplexation of the [2]pseudorotaxanes 3a and 3b in a polar solvent (DMSO-d6/CDCl3), obtaining activation volumes of −0.9 and −0.4 cm3 mol−1, respectively, at 303 K and zero pressure. Moreover, we calculated the activation parameters for the decomplexation processes on the basis of transition state theory at each pressure.

A 50% EtOH extract of the dried endosperms of melinjo (Gnetum gnemon L.) was purified by a combination of column chromatography, including highly porous polymer, octadecylated silica (ODS), hydroxypropylated dextran (LH-20), and silica gel, resulting in the isolation of a new stilbenoid 1, named gnetin L, along with five previously identified stilbenoids 2−6 (gnetin C, gnemonosides A, C, and D, and resveratrol). All of these stilbenoids showed 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity similar to that of ascorbic acid and dl-α-tocopherol. With the exception of gnemonoside A (3), these stilbenoids showed moderate antimicrobial activity. Inhibition of lipase from porcine pancreas was recognized in four stilbenoids excluding gnemonoside A (3) and resveratrol (6). Gnetin C (2), gnemonoside C (4), and gnemonoside D (5) inhibited the hydrolysis of starch by α-amylase from porcine pancreas. An EtOH extract containing these stilbenoids also showed DPPH radical scavenging effect, lipase and α-amylase inhibition activity, and antimicrobial activity against food microorganisms and enterobacteria. The present study indicates that melinjo and extracts containing these constituents are useful as health supplements.

This communication describes the base- and acid-induced five-state translational isomerization of a [3]rotaxane containing two pairs of N-arylamine and N-alkylamine centers as binding sites for two dibenzo[24]crown-8 components. Gradual molecular shuttling of this [3]rotaxane is achieved in response to both the amount and strength of the added acid or base.

This paper describes the acid/base-mediated three-state translational isomerization of two [2]rotaxanes, each containing N-alkylaniline and N,N-dialkylamine centers as binding sites for threaded dibenzo[24]crown-8 units. Under neutral conditions, the dialkylamine unit predominantly recognized the crown ether component through cooperative binding of a proton; when both amino units were protonated under acidic conditions, both translational isomers were generated; the addition of a strong base caused aniline–crown ether interactions to dominate. The three states of the [2]rotaxane featuring the 3,5-diphenylaniline terminus in its dumbbell-shaped component were accompanied by distinct absorptive outputs that were detectable using UV spectroscopy.