The ability of macroheterocyclic compounds to complex with ionic species has led to the synthesis and investigation of many multidentate macroheterocyclic species . The most stable complexes are formed between macrocyclic polyetheral ligands (crown ethers) with alkali or alkaline earth metal iona. There is an excellent correlation of the stability of these complexes with the size of the cation ...

Crown ethers have the remarkable property of recognizing and binding specific metal cations in complex mixtures. We propose to combine molecular recognition with molecular electric conductance. The question we address is: can the event of binding a cation be sensed by a change in conductance? Specifically, we study a short molecular wire (MW) containing a crown-6 molecule connected via sulfur a...

VI.

Nitrobenzofurazan derivatives are well known for their fluorescence, whilst crown ethers complexing capacity toward cationic species. In this study, we present the synthesis and structural characterization of a new derivative containing both nitrobenzofurazan moieties ether core. The compound was obtained from dibenzo-18-crown-6 ether, which first nitrated, reduced to corresponding amine, subse...

An efficient procedure for preparing enantiopure polycyclic ethers is reported. The protocol is based on the photo-oxidation/conjugate addition sequence over a chiral functionalized furan, which was prepared from commercially available tri-O-acetyl-D-glucal. The Michael addition step afforded two products with the same absolute configuration from a mixture of diastereomers.

The asymmetric ring-opening of meso-aziridines with primary alcohols is realized using an N,N'-dioxide-Mg(OTf)2 complex as the catalyst. The desired vicinal trans-β-amino ethers are afforded in good yields and enantioselectivities. Aniline and water could also be used as the nucleophiles for the ring-opening in an identical catalyst system.

Single-crystal to single-crystal transformations are possible by ion-exchange and transport reactions through supramolecular channels that are composed of crown ether molecules and use trihalide ions as scaffolds. Kinetic measurements of ion transport at different temperatures provide activation energy data and show that a very fast exchange of K(+) ions with Na(+) ions occurs.