Imidazolium-based macrocycles as multisignaling chemosensors for anions?

Dalton Transactions Pub Date: 2008-05-28 DOI: 10.1039/B719115D

Abstract

A series of structurally novel anion receptors 3, 4, and 5 in which a ferrocene unit and a fluorescent moiety are linked to two imidazolium rings have been designed and prepared from 1,1′-bis(imidazolylmethyl)ferrocene. Their crystal structures revealed that these receptors are capable of incorporating anions such as PF6? and Br?. Consequently, the anion binding studies were carried out using various techniques including electrochemistry (CV and OSWV), fluorescence, UV-vis, and 1H NMR spectroscopy. All the receptors showed a special electrochemical response to the F? anion with a remarkable cathodic shift of more than 260 mV and displayed a unique selectivity for F? and AcO? anions with fluorescence enhancement over various other anions of present interest (Cl?, Br?, I?, HSO4?, H2PO4?). In addition, for receptor 5, obvious absorption changes were observed when the H2PO4? anion was added while other anions (F?, Cl?, Br?, I?, AcO?, HSO4?) showed only a minor influence on the UV-vis spectra. 1H NMR titrations demonstrated that receptors 3 and 4 can bind anions through (C–H)+?X?hydrogen bonds and showed strong affinity and high selectivity for the AcO? anion in acetonitrile.

Graphical abstract: Imidazolium-based macrocycles as multisignaling chemosensors for anions
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